13355 Learner Guide web 15Sept06 - AgriSeta · 2006. 10. 12. · Dear Learner - This Learner Guide contains all the information to acquire all the knowledge and skills leading to

LLeeaarrnneerr GGuuiiddee PPrriimmaarryy AAggrriiccuullttuurree

TThhee eennvviirroonnmmeenntt aanndd iittss rreellaattiioonnsshhiipp ttoo ssuussttaaiinnaabbllee

ccrroopp pprroodduuccttiioonn

My name: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Company: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commodity: . . . . . . . . . . . . . . . . . . . . Date: . . . . . . . . . . . . . . .

NQF Level: 1 US No: 13355

The availability of this product is due to the financial support of the National Department of Agriculture and the AgriSETA. Terms and conditions apply.

Demonstrate an understanding of the physical and biological environment and its relationship to sustainable crop production

Primary Agriculture NQF Level 1 Unit Standard No: 13355 22

Version: 01 Version Date: July 2006

BBeeffoorree wwee ssttaarrtt…… Dear Learner - This Learner Guide contains all the information to acquire all the knowledge and skills leading to the unit standard:

Title: Demonstrate an understanding of the physical and biological environment and its relationship to sustainable crop production

US No: 13355 NQF Level: 1 Credits: 4

The full unit standard will be handed to you by your facilitator. Please read the unit standard at your own time. Whilst reading the unit standard, make a note of your questions and aspects that you do not understand, and discuss it with your facilitator.

This unit standard is one of the building blocks in the qualifications listed below. Please mark the qualification you are currently doing:

Title ID Number NQF Level Credits Mark

National Certificate in Animal Production 48970 1 120

National Certificate in Mixed Farming Systems 48971 1 120

National Certificate in Plant Production 48972 1 120

You will also be handed a Learner Workbook. This Learner Workbook should be used in conjunction with this Learner Guide. The Learner Workbook contains the activities that you will be expected to do during the course of your study. Please keep the activities that you have completed as part of your Portfolio of Evidence, which will be required during your final assessment.

You will be assessed during the course of your study. This is called formative assessment. You will also be assessed on completion of this unit standard. This is called summative assessment. Before your assessment, your assessor will discuss the unit standard with you.

EEnnjjooyy tthhiiss lleeaarrnniinngg eexxppeerriieennccee!!

Are you enrolled in a: Y N

Learnership?

Skills Program?

Short Course?

Please mark the learning program you are enrolled in:

Your facilitator should explain the above concepts to you.




HHooww ttoo uussee tthhiiss gguuiiddee …… Throughout this guide, you will come across certain re-occurring “boxes”. These boxes each represent a certain aspect of the learning process, containing information, which would help you with the identification and understanding of these aspects. The following is a list of these boxes and what they represent:

What does it mean? Each learning field is characterized by unique terms and definitions – it is important to know and use these terms and definitions correctly. These terms and definitions are highlighted throughout the guide in this manner.

You will be requested to complete activities, which could be group activities, or individual activities. Please remember to complete the activities, as the facilitator will assess it and these will become part of your portfolio of evidence. Activities, whether group or individual activities, will be described in this box.

Examples of certain

concepts or principles to help you contextualise them easier, will be shown in this box.

The following box indicates a summary of concepts that we have covered, and offers you an opportunity to ask questions to your facilitator if you are still feeling unsure of the concepts listed.

MMyy NNootteess …… You can use this box to jot down questions you might have, words that you do not understand,

instructions given by the facilitator or explanations given by the facilitator or any other remarks that

will help you to understand the work better.

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WWhhaatt aarree wwee ggooiinngg ttoo lleeaarrnn??

What will I be able to do? ................................................................................... 5

Learning Outcomes .............................................................................................. 5

What do I need to know? .................................................................................... 5

Session 1: Identify and describe the nature of soil …………………………… 6

Session 2: Climatic factors that influence crop production ………………… 23

Session 3: The importance of water in crop production ……………………… 28

Session 4: The influence of topography on crop production …………………. 33

Session 5: Biological organisms which influence crop production ……….. 38

Session 6: The effects of crop production practices on the sustainability of the environment ………………………………………………………

48

Glossary ……………………………………………………………………… 52

Bibliography ............................................................................... 55

Terms & Conditions .................................................................... 55

Acknowledgements .................................................................... 56

SAQA Unit Standard




WWhhaatt wwiillll II bbee aabbllee ttoo ddoo?? When you have achieved this unit standard, you will be able to:

Identify and describe the nature of soil

Analyse soil as a factor in crop production

Identify and describe climatic factors influencing crop production and their practical implications

Identify and describe the importance of water as a factor in crop production

Identify and describe the influence of topography on crop production

Identify, describe and explain the biological organisms as a factor influencing crop production

Assess the effects of crop production practices on the sustainability of the environment.

LLeeaarrnniinngg OOuuttccoommeess At the end of this learning module, you must is able to demonstrate a basic knowledge and understanding of:

crop production practices which enhance environmental sustainabililty,

mulching,

crop rotation,

stubble mulching,

green manure,

composting.

WWhhaatt ddoo II nneeeedd ttoo kknnooww??

No learning is assumed to be in place.




SSeessssiioonn 11

IIddeennttiiffyy aanndd ddeessccrriibbee tthhee nnaattuurree ooff ssooiill

After completing this session, you should be able to: SO 1: Identify and describe the nature of soil.

SO 2: Analyse soil as a factor in crop production.

In this session we explore the following concepts: What are the physical properties of soil? “Soil is a product of its environment” Let’s identify soil components

Let’s identify soil texture The descriptions of soil textures Let’s identify soil structure

What are the reasons why soil is a factor in crop production? Which factors affect the role of soil in crop production? Which factors improve soil productivity and crop production?

Ways to overcome soil limitations in crop production

Why Is Soil Important?

Soil is important for plants because it holds roots, stores nutrients, and provides support for plants. This module helps you search for secrets in the soil. It will help you uncover the ingredients of soil that are important to plant growth.

What do all living things need in order to live?

Which of these things do plants get from the soil?

What part or parts of the soil do you think contain these things?

Please complete Activity 1 in your learner workbook

MMyy NNootteess …… . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .




1.1 UUnnddeerrssttaannddiinngg tthhee bbaassiiccss ooff ssooiill pprrooppeerrttiieess..

Soil is the thin layer of eroded mineral material, broken down organic matter and community of animals, plant roots and micro organisms that cover the terrestrial surface of the earth.

Although we rarely notice the soils around us, we rely on soil to produce our food, to clean our water, to play on and in (and with!) and as a solid base for our buildings.

Soil is our greatest resource, yet every year, soil that could be growing crops or pastures is lost, through erosion, acidity, salinity, pollution and housing estates.

We are going to look at what soil is, how it works, what we do with it, how we damage it and how we can restore it.

Erode To break down into smaller pieces.

Organic Derived from living organisms such as plants, animals, fungi or bacteria.

Micro-organism An organism so small, that it can often only be seen under a microscope.

Terrestrial Of the land (opposite to aquatic, aerial). Living on the ground.

The diagram below lists the basic features of soil.




1.2 SSooiill tteexxttuurree aanndd ssttrruuccttuurree

Soil texture

Texture: The coarseness or fineness of the soil.

Sand Particles: The largest of the soil particles. It is huge when it is compared to clay.Silt Particles: This is the medium-sized soil particle. It is between sand and clay in

size. Clay particles: Very fine soil particles.

The way soil "feels" is called the soil texture.

Soil texture depends on the amount of each size of particle in the soil. Sand, silt, and clay are names that describe the size of individual particles in the soil.

Sand Is the largest particles (0.05 to 2.0 mm in diameter) and it feels "gritty."

• Sand (excluding gravel) is the largest of the soil particles. • When you rub it, it feels rough. • This is because it has sharp edges. • Sand doesn't hold many nutrients or a lot of water.

Silt Is medium sized (more than 0.002 mm but less than 0.05 mm in diameter), and they feel soft, silky or "floury."

• Is a soil particle whose size is between sand and clay. • Silt feels smooth and powdery. • When wet it feels smooth but not sticky.

Clay Is the smallest sized particles (less then 0.002 mm in diameter), and they feel "sticky" and they are hard to squeeze.

• Is the smallest of the soil particles. • Is smooth when dry and sticky when wet. • Soils high in clay content are called heavy soils. • Hold a lot of water and nutrients, but too much water can

replace the air




Particle size has a lot to do with a soil's drainage and nutrient holding capacity. To better understand how big these three soil particles are, think of them like this:

If a particle of sand were the size of a soccer ball, then silt would be the size of a tennis ball, and clay would be the size of a table tennis ball. Line them all up, and you can see how these particles compare in size ratio.

Please complete Activity 2 & 3 in your learner workbook

MMyy NNootteess …… . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The importance of soil texture

♦ The texture of a soil influences how the soil responds to different stresses.

♦ Sandy soils are much better drained than clay soils.

♦ In a heavy rain, sandy soils allow the water to freely enter and wash through.

♦ Clay soils can be poorly drained and water might start accumulating on the surface.

♦ However, sandy soils dry out much quicker than clay soils.

For most agricultural plants, loamy soils are generally the best because they are well drained, but still retain water longer than sandy soils.

In general, the finer the texture;

• the more difficult a soil is to work or till, • the greater the water holding capacity, • the slower water will enter and move through the soil profile, • the more difficult plant root penetration, • the more readily surface soil will crust, and • the more nutrient rich the soil.

Regardless of textural class, all soils in South Africa contain sand, silt, and clay, although the amount of a particular particle class may be small.




Soil structure Soil structure is the shape that the soil takes based on its physical and chemical properties. Each individual unit of soil structure is called a ped. Take a sample of undisturbed soil in your hand (either from a shovel or auger). Look closely at the soil in your hand and examine its structure.

Possible choices of soil structure are:

Granular: Resembles cookie crumbs and is usually less than 0.5 cm in

diameter.

Blocky: Irregular blocks that are usually 1.5 - 5.0 cm in

Prismatic: Vertical columns of soil

that might be a number of cm long. Usually found in lower

horizons.

Columnar: Vertical columns of soil that have a salt "cap" at the top. Found in soils of arid climates.

Platy: Thin, flat plates of soil that lie horizontally. Usually found in

compacted soil.

Single Grained: Soil is broken

into individual particles that do not stick together. Always

accompanies a loose consistence. Commonly found

in sandy soils.

Massive: Soil has no visible structure, is hard to break apart and appears in very large clods.




Soil with structure:

Granular

Blocky

Prismatic

Columnar

Platy

Structureless soils:

Single grained

Massive




Soil types

Textural Class Shape of sausage Clay Content Illustration

Sand It is not possible to roll a sausage in the palm. The soil does not stick together.

Less than 10%

Loamy Sand (LoSa)

It is possible to roll a sausage, but the sausage cannot be bent at all without cracking or breaking.

10 to 15%

Sandy Loam (SaLo)

The sausage can be bent slightly, with the tips bent downwards for about 10mm without the sausage cracking in the middle.

15 to 25%

Sandy Clay Loam (SaClLo)

The sausage can be bent down at the tips to about 20mm without cracking in the middle.

25 to 35%

Sandy Clay The sausage can be bent to form a semi-circle without cracking in the middle.

35 to 50%

Clay

The sausage can be bend to form a complete circle without cracking in the middle.

>50%

Any soil can be placed within the Soil Textural Triangle, once the relative proportions of clay, silt and sand are known.

The texture of a soil influences how the soil responds to different stresses.





MMyy NNootteess …… . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Soil Consistency Soil Consistency the feel of the soil, reflecting relative resistance to pressure: e.g. friable, firm, hard, loose, plastic. The term soil consistency is used to describe the resistance of a soil at various moisture contents to mechanical stresses or manipulations. It is commonly measured by feeling and manipulating the soil by hand or by pulling a tillage instrument through it. The consistency of soils is generally described at three soil moisture levels: wet, moist and dry.

Terms used to describe soil consistency at these three moisture levels are shown in the Table below.

Wet soils

Stickiness Plasticity Moist soils Dry soils

Non-sticky No plastic Loose Loose

Slightly sticky Slightly plastic Very friable Soft

Sticky Plastic Friable Slightly hard

Firm Hard

Very firm Very hard Very sticky Very plastic

Extremely firm Extremely hard




The organic content of soil


MMyy NNootteess …… . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The soil cycle describes, in brief, the processes through which soil is formed. Rocks are weathered though physical processes by the wind and water. When the rocks weather water carries mineral particles originating from the rocks to lower lying areas. Soil microbes degrade dead animal and plant material as well as faecal material forming organic matter. The organic matter combines with the mineral particles, forming the basis of soil. This process does not occur quickly, but rather over a period of hundreds to thousands of years.

The further decay of organic matter releases nutrients that are taken up by plants, and used for plant growth. The plants will develop, form seed and die according to its specific life-cycle. The dead plant material is then fed back into the system becoming organic matter.

Living plants are used by animals as a food source aiding in the growth process for the animals that feed on the plants. The animals leave behind faecal matter and residues from the plants that cannot be fully utilised. Eventually the animals die, and are also returned to soil as organic matter. This cyclic process that occurs in the formation and upkeep of soil is an ongoing process leading to enrichment of the soil and providing a basis for ecosystem development.




In the same way in which soil is formed and cycled, so also individual nutrients go though a cycling process. The end result is that no physical matter is lost, it merely goes through various phases of transformation. In the diagram above, natural weathering of rock releases mineral particles. These combine with organic matter deposited by birds on the land. The organic matter originates from the oceans, either as marine plants or animals that are eaten by the birds. Nitrogen from the atmosphere, is fixed in the soil through micro-organisms, thereby enhancing the soil nitrogen content. Elements such as sulphur originating from the ocean may be cycles ending up in soil. As soil is degraded, or as soil is transported into the oceans, these nutrients are again released into water. The elements can then again escape the water environment though various processes.




Type of Soil Example of Test Jar

Sandy soils are found throughout South Africa, and are very common near the mountain foothills, along rivers and streams and certain coastal areas. Sandy soils are typically comprised of approximately 80 - 100% sand, 0 - 10% silt and 0 - 10% clay by volume. Sandy soils are light and typically very free draining, usually holding water very poorly due to very low organic content.

Loam soils are also common in Southern Africa, particularly in the valleys and flat areas (flood plains) surrounding rivers and streams. Loam soils are typically comprised of approximately 25 - 50% sand, 30 - 50% silt and 10 - 30% clay by volume. Loam soils are somewhat heavier than sandy soils, but also tend to be fairly free draining, again, due to typically low organic content.

Clay soils are very common in certain areas, particularly around urban areas where fill soils have been used to establish grade in subdivisions and developments. Clay soils are typically comprised of approximately 0 - 45% sand, 0 - 45% silt and 50 - 100% clay by volume. Clay soils are not typically free draining, and water tends to take a long time to infiltrate. When wet, such soils tend to allow virtually all water to run-off. Clay soils tend to be heavy and difficult to work when dry.

Biodiversity A measure of the number of different types of species. An area with a

high biodiversity (such as a rainforest or a tropical reef) has many different kinds of organisms present.

Virus A tiny, simple micro-organism that replicates itself by invading the cells of other organisms and changing the function of the cells so that they start producing viruses.

Bacteria Single-celled micro-organisms. Decompose The process whereby soil microbes and animals eat organic material,

breaking it down into smaller and smaller pieces. This process recycles the nutrients found in the organic material, making the nutrients available for further plant growth.

Aerate Expose to air, usually by mixing material with air, or creating spaces for air to move into.




Identifying soil structure and texture with simple tests and observations.

Soil Horizons: - In the diagram below, you can see the different layers of soil.

Non decomposed litter

Partly decomposed debris

Zone of humus accumulation

Zone of strongest leaching

Transition to B horizon

Transition to A horizon

Zone of strongest deposition

Transition to C horizon

Unconsolidated rock

Simple tests and observations can help us determine soil composition and texture.

Soil Consistency.

Take a ped from the topsoil horizon. If the soil is very dry, moisten the face of the profile using a water bottle with a squirt top, and then remove a ped to determine consistence. Holding it between your thumb and forefinger, gently squeeze the ped until it pops or falls apart.

Loose You have trouble picking out a single ped and the structure falls apart before you handle it.* * Soils with "single grained" structure always have a loose consistency.

Friable The ped breaks with a small amount of pressure.




Firm The ped breaks when you apply a good amount of pressure and dents your fingers before it breaks.

Extremely Firm The ped can't be crushed with your fingers (you need a hammer!).

Presence of roots and rocks in your soil.

Presence of Roots Observe and record if there are none, few, or many roots in the horizon.

Presence of Rocks Observe and record if there are none, few, or many rocks* in the horizon. * A rock is defined as being larger than 2 mm in size.


MMyy NNootteess …… . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .




Water holding and drainage capacity of different soil types.

A simple check will help you identify problems and note things that may need changing. Doing this before you start planting will make gardening a whole lot more fun and keep you from having to correct mistakes when plants are growing.

Check for good drainage. Does water sit on top of the ground for a long time? Does the soil stay wet for a long time? A spot like this might be good for mud pies but not for gardening.

♦ Soil drainage is defined as the rate and extent of water movement in the soil, including movement across the surface as well as downward through the soil.

♦ Slope is a very important factor in soil drainage. The steeper the slope, the more and the faster water will run downhill if cultivation was not adapted (contouring) to these conditions.

♦ Other factors include texture, structure, and physical condition of surface and subsoil layers.

♦ Soil drainage is indicated by soil colour. Clear, bright colours indicate well-drained soils.

♦ Mixed, drab, and dominantly grey colours indicate poor drainage.

♦ Low-lying areas within the landscape receive run-off water.

♦ Frequently, the water from these areas must escape by lateral movement through the soil or by evaporation from the surface, as poor structure and other physical influences do not allow drainage through the soil.

♦ Continuous, cemented hardpan layers such as caliche also greatly reduce the internal drainage through a soil profile.

Sandy soils are much better drained than clay soils. In a heavy rain, sandy soils allow the water to freely enter and wash through. But clay soils can be poorly drained and water might start accumulating on the surface. However, sandy soils dry out much quicker than clay soils. For most agricultural plants, loamy soils are generally the best because they are well drained, but still retain water longer than sandy soils.

Water holding capacity refers to the soil’s ability to stay wet after irrigation/rainfall. Clay soils stay wet for longer than sandy soils. This implies that sandy soils should receive less water, more often than clay soils to prevent the crops from experiencing water stress.




Air and water movement in Soil

♦ Air and water movement within the soil is closely related to soil structure.

♦ Good soil structure allows rapid movement of air and water, while poor soil structure slows down this movement.

♦ Other things being equal, water can enter a surface soil that has granular structure more rapidly than one that has little structure.

♦ Soil compaction due to excessive vehicle or foot traffic or excessive tillage can greatly reduce soil aggregation and water infiltration.

♦ Since plant roots move through the same channels in the soil as air and water, good structure allows extensive root development whereas poor structure discourages it.

♦ Water, air, and plant roots move more freely through sub soils that have blocky structure than those with a flaky horizontal structure.

♦ Good structure of the surface soil is promoted by an adequate supply of organic matter.

♦ Soil structure can be protected, by working the soil only when moisture conditions are correct.

The importance of soil pH

pH is a measure of how acidic or basic things are and is measured using a pH scale between 0 to 14, with acidic things having a pH between 0-7 and basic things having a pH from 7 to 14. For instance, lemon juice and battery acid are acidic and fall in the 0-7 range, whereas seawater and bleach are basic (also called "alkaline") and fall in the 7-14 pH range. Pure water is neutral, or 7 on the pH scale.

The pH of soil, or more precisely the pH of the soil solution, is very important because the soil solution carries nutrients such as Nitrogen (N), Potassium (K), and Phosphorus (P) that plants need in specific amounts to grow, thrive, and fight off diseases.




If the pH of the soil solution is increased above 5.5, Nitrogen (in the form of nitrate) is made available to plants. Phosphorus, on the other hand, is available to plants when soil pH is between 6.0 and 7.0.

Certain bacteria help plants obtain N by converting atmospheric Nitrogen into a form of N that plants can use. These bacteria live in root nodules of legumes (like alfalfa and soybeans) and function best when the pH of the plant they live in is growing in soil within an acceptable pH range.

For instance, alfalfa grows best in soils having a pH of 6.2 - 7.8, while soybean grows best in soils with a pH between 6.0 and 7.0. Peanuts grow best in soils that have a pH of 5.3 to 6.6. Many other crops, vegetables, flowers and shrubs, trees, weeds and fruit are pH dependent and rely on the soil solution to obtain nutrients.

If the soil solution is too acidic plants cannot utilize N, P, K and other nutrients they need. In acidic soils, plants are more likely to take up toxic metals and some plants eventually die of toxicity (poisoning). If the soil is, however, too alkaline, the soil mobility of especially micronutrients reduces and plants experience deficiencies. These deficiencies can lead to poor growth, reproduction and yield in the crop.

Herbicides, liquid fertilisers, fungicides and other chemicals are used on and around plants to fight off plant diseases and get rid of bugs that feed on plants and kill plants. Knowing whether the soil pH is acidic or basic is important because if the soil is too acidic the applied liquid fertilisers, herbicides, and fungicides will not be absorbed (held in the soil) and they will end up in garden water and rain water runoff, where they eventually become pollutants in our streams, rivers, lakes, and ground water.

Deep vs. shallow soils

Very Shallow — surface is less than 20cm from a layer that retards root development. Shallow — Soil surface is 20-40 cm from a layer that retards root development.

Moderately deep — Soil surface is 40-60 cm from a layer that retards root development. Deep — Soil surface is 70-120 cm from a layer that retards root development. Very deep — Soil surface is 120 cm or more from a layer that retards root development.




Concept I understand this concept

Questions that I still would like to ask

Identify and describe the nature of soil.

Physical properties of soil

The principle that soil is a product of its environment is described.

Soil components are identified.

Soil texture is identified.

Soil texture is described.

Soil structure is identified.

Analyse soil as a factor in crop production.

Reasons why soil is a factor in crop production are provided.

Factors affecting the role of soil in crop production are described.

The concept of soil productivity is explained.

Factors that improve soil productivity and crop production are investigated.

Soil limitations in crop production are identified.

Ways to overcome soil limitations in crop production are explained and justified.





SSeessssiioonn 22

CClliimmaattiicc ffaaccttoorrss tthhaatt iinnfflluueennccee ccrroopp pprroodduuccttiioonn After completing this session, you should be able to: SO 3: Identify and describe climatic factors that influence crop production and explore their practical implications.

In this session we explore the following concepts:

Identify the climatic factors influencing crop production

Describe climatic factors influencing crop production

Influence of climatic factors on crop production

Crop production practices that can be adapted to climatic factors

2.1 Identify the climatic factors influencing crop production

Weather and Climate

Do you know the difference between weather and climate?

Weather

Climate

Weather is the day-to-day condition of the atmosphere. This includes temperature, precipitation (rainfall, snow, hail), humidity and wind.

Climate is the average weather conditions of a place, usually measured over one year. This includes temperature and rainfall.


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2.2 Describe climatic factors influencing crop production

Climate vs crop

Specific crops need specific climates in order to produce an optimum quality and quantity crop. Deciduous Fruit, Stone Fruit, Pome Fruit & Wine Grapes: Cultivars differ with respect to the intensity of cold required for them to drop their leaves and then to begin budding again simultaneously.

Some apple cultivars need more sunshine to develop good colour. Cold, wind, rain, sunshine and humidity together constitute the climate, which determines the growth vigour and the crop quality, and size produced by the fruit trees.

Subtropical fruit: Different cultivars, of the same species, are tolerant of a wide range of climatic conditions. It is successfully cultivated under conditions which vary from very hot, very humid to cool and dry, to very hot and arid. Climatic conditions in a specific area will, firstly determine whether mangoes can be cultivated commercially in the given area, and secondly, will influence the choice of cultivars. It is advised that the average temperature during winter should preferably be above 5 ˚C. For optimum growth, and production, the average maximum temperature should be between 27 and 36 ˚C.

Other crops: Each plant species, has it’s own critical temperatures at which it performs best. It is therefore important to know these temperature requirements in order to choose the best crop for the specific climate in your production area. The optimum temperatures for growth of some crops are given in the table below. In general the cool weather crops like beetroot, beans, carrot etc. have an optimum growth temperature of between 15 and 20°C, while the warm weather crops like tomato, pumpkin, cotton etc. have an optimum of 20 to 30°C.




2.3 Influence of climatic factors on crop production

Optimum growth temperatures for some vegetable and field crops.

Crop Optimum temperature (°C) Green beans 15 – 20 Beetroot 15 – 20 Carrot 15 – 20 Cucumber 20 – 34 Lettuce 15 – 20 Onion 12 – 24 Pumpkin 20 – 24 Swiss chard / Spinach 15 – 24 Tomato 22 – 24 Watermelon 22 – 30 Cotton 20 – 30 Groundnuts 22 - 28

If one does not adhere to the recommended temperatures, the crops can experience stress, which makes them more prone to disease, and insect attacks and they also produce and grow very poorly. Temperature stress is usually experienced at temperature extremes like frost (±0°C for all crops) or very high temperatures like averages of 25 - 30°C for cool weather crops and 35 – 40°C for warm weather crops.

Hail can partially or totally destroy a crop or cause such severe damage that the fruits and vegetables cannot be sold. It is thus important that one should know what the changes and frequency of hail in a specific area is, to take steps in protecting the crop. Ways to protect the crop include the erection of hail nets over tomato and other fruit/berry crops or the planting of crops which bears the crop below the soil.

Wind can also damage our crops. Again, make sure what the chances of strong winds are in your area and plant or erect wind breaks to protect the crop.


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2.4 Crop production practices that can be adapted to climatic factors

Dry land Farming

Dry land farming is an agricultural technique of cultivating land which receives little rainfall. In addition no dams or irrigation systems will be available.

OR Dry land farming is practiced in areas that receive sufficient rainfall to sustain the crop through sufficient soil moisture – thus no irrigation is necessary. Annual crops can only be established under dry land conditions when sufficient water has accumulated in the soil profile to facilitate germination. In this case planting dates should be adjusted according to rainfall.

Irrigated Farming

Irrigation is a key factor in the agricultural economy of many parts of the world. Irrigation farming refers to a system where water is moved from a water source to the area where farming activities are taking place trough furrows, pipes or other systems. The water is then applied manually or mechanically to the farming activity by means of sprinklers, dripping etc.

Hydroponic Farming

Hydroponics farming is: The growing of plants in a water medium without soil There are nutrients added to the water. It is the most productive way to grow all varieties of plants, and those raised in a hydroponics system will exhibit maximum yield, flavour, vitamin and essential oil content. To set up a hydroponics system requires considerable capital.

Other ways to adapt production practices to climatic factors it to make use of windbreaks and hail netting to protect the crop against wind and hail respectively (See section on climatic factors influencing crop production). Shade netting can be used to protect fruit against sunburn. If high temperature is prevalent, and irrigation water is available, regular light irrigation can be used to cool down the plants preventing heat stress.







Climatic factors influencing crop production are identified.

Climatic factors influencing crop production are described.

The influence of climatic factors on crop production is explained.

Crop production practices that can be adapted to climatic factors are investigated and reported.

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SSeessssiioonn 33 TThhee iimmppoorrttaannccee ooff wwaatteerr

iinn ccrroopp pprroodduuccttiioonn After completing this session, you should be able to: SO 4: Identify and describe the importance of water as a factor in crop production.


Identify sources of water

How water plays a role in crop production

Water as a finite resource in crop production

Optimal use of water resources in crop production

Significance of water in crop production

3.1 Identify water sources

Water Sources

Water sources include water provided by municipalities, wells, ponds, reservoirs, canals, ditches, streams or rivers. The water used needs to be clean in order to be used within the small holes of dripper or micro jet irrigation devices, in order to prevent the clogging of pores.

Ground water from wells is generally of good quality and should be used when possible. It may contain sand or chemical precipitates.

Surface water such as streams, springs and ponds can be used, but you should guard against bacteria, algae and other aquatic life.


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3.2 How water plays a role in crop production

Water is important in the plant's ability to make food, take up and transport nutrients in the plant itself. Without water or with too much water, a plant dies. For this reason, watering is an important part of plant care. Most plants like to be watered when the soil is slightly dry to the touch. When watering a pot plant, moisten the soil by using enough water so that it starts to come out of the hole in the bottom of the container.

(This is why it is important to use containers with drainage holes.) How often you water depends on a lot of things. Plant size, time of the year, and type of plant are a few. Your best guide, though, is to feel the soil. If you stick your finger one inch into the soil and it is dry, then water your plant.

Without water no plants can grow!

Apart from the mentioned role of water in the plant, one also has to remember that plants can overheat. To prevent that, the plants transpire (same as people perspiring). If there is no water or too little water, plants can thus overheat.

3.3 WWaatteerr iiss aa ffiinniittee rreessoouurrccee iinn ccrroopp pprroodduuccttiioonn

Water is necessary to all living things.

Water is all around us, in the air and in the ground. It is in milk, vegetables, fruit, meat, leaves, trunks, roots, and branches of a tree; it is even in stones.

Despite that water is in and around us it is a limited resource. If it does not rain, the dams become empty and there is no water in the boreholes, plants will die. We humans are not able reproduce (make) water, so if it is finished it is finished.




3.4 Optimal use of water in crop production

In order to understand irrigation systems and the need for irrigation systems, we first have to understand what happens when water land on soil whether it comes from rain or irrigation. It also does not matter what irrigation system is used because we want to deal with water being applied on the soil and what happens with it after that.

One could ask why should we know what happens with water after it landed on the soil? Is it important? Is our job, as irrigators not finished when we put the water on the soil?

A few things can happen to water on the soil. It could infiltrate into the soil or some can run off and get back into the river. As we have heard before if there is too much water it can cause erosion or over irrigation or water logging or a combination of all three. If we apply too little water the crop will suffer and we could get a build up of salt.

In irrigation farming one of the most common problems is over irrigation.

We need to be aware how it affects our crop, our soil and thus our farming profits.

What happens exactly during the irrigation process? Let us look at it when water reached the ground surface. Water starts to move down into the soil, mainly because of the "sucking power" of the soil. The dryer the soil is the more is this sucking power of the soil. This is also why water moves sideways in soil and not only downward. Just after irrigation the soil is "wet", that means that all the air is pushed out of the little openings in the soil. After a day or so the soil is "damp", that means some of the openings in the soil is filled with water and some with air. When the soil is damp like this the plant roots can easily "drink water" and "breathe air". This is the best condition of the soil for plant growth. When soil is dry, plants cannot get any water from it and plants are damaged. Irrigation should take place before it gets too difficult to get water from the soil or simply before the soil gets too dry.

In irrigation farming, one then has to apply the right amount of water at the right time. In doing so, only the water needed by the plant will be applied and water can be saved and or be used more efficiently.




Even in dry land farming water can be managed. Rainwater can be used more efficiently by making use of mulches. These mulches prevent excessive evaporation from the soil surface, improve infiltration and prevent soil erosion.

Other ways to preserve rainwater is by making use of rainwater harvesting. A simple way of doing it is by making small dams in the rows between the crop. When it then rain, the water can pond in these dams and not simply flow away along the soil surface.


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3.5 Significance of water in crop production

Water is needed during the process which carbohydrates are produced in the plant cells. The carbohydrate gives energy to the plant to grow and reproduce. Without water, none of these processes can happen and the farmer has little or nothing to harvest.

In South Africa most crops have to be irrigated in order to become viable commercial farming crops.




Concept I

understand this concept


Identify and describe the importance of water as a factor in crop production.

Sources of water are identified.

The role of water in crop production is explained.

The principle of water as a finite resource in crop production is explained.

The optimal use of water resources in crop production is explained.

Conclusions regarding the significance of water in crop production are drawn.

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SSeessssiioonn 44

TThhee iinnfflluueennccee ooff ttooppooggrraapphhyyoonn ccrroopp pprroodduuccttiioonn.. After completing this session, you should be able to: SO 5: Identify and describe the influence of topography on crop production.


What is topography?

How topography influences crop production

Evaluate topography as a factor influencing crop production practices

How to overcome topographical limitations in crop production

4.1 What is topography?

Topography is the natural factors that will influence a specific area situated in a specific place, such as:

♦ the shape and lie of the land (geography),

♦ its relation to oceans and mountain ranges,

♦ its climate,

♦ its geographical history,

♦ its slope directions and elevation,

♦ its location in terms of latitude and longitude.




Topography of South Africa

South Africa lies between 22 and 35 degrees south, flanked on the west by the Atlantic Ocean and on the east by the Indian Ocean, whose waters meet at the country's most southern tip, Cape Agulhas. The long coastline stretches more than 2 500 kilometres from a desert border in the north-west, down the icy and treacherous Skeleton Coast to Cape Agulhas, then up along rolling green hills and wide beaches fronting the warm Indian Ocean, to a border with subtropical Mozambique in the north east.

Geography and climate of South Africa

South Africa occupies the southern tip of Africa, its long coastline stretching more than 2 500km from the desert border with Namibia on the Atlantic coast southwards around the tip of Africa and then north to the border with subtropical Mozambique on the Indian Ocean.

The low-lying coastal zone is narrow for much of that distance, soon giving way to a mountainous escarpment that separates it from the high inland plateau. In some places, notably the province of KwaZulu-Natal in the east, a greater distance separates the coast from the escarpment.

Although the country is classified as semi-arid, it has considerable variation in climate as well as topography.

The great inland Karoo plateau, where rocky hills and mountains rise from sparsely populated scrubland, is very dry, and gets more so as it shades in the north-west towards the Kalahari desert. Extremely hot in summer, it can be icy in winter.

In contrast, the eastern coastline is lush and well watered, a stranger to frost. The southern coast, part of which is known as the Garden Route, is rather less tropical but also green, as is the Cape of Good Hope - the latter especially in winter. This south-western corner of the country has a Mediterranean climate, with wet winters and hot, dry summers. Its most famous climatic characteristic is its wind, which blows intermittently virtually all year round, either from the south-east or the north-west.

The eastern section of the Karoo does not extend as far north as the western part, giving way to the flat landscape of the Free State, which though still semi-arid receives somewhat more rain. North of the Vaal River the Highveld is better watered and saved by its altitude (Johannesburg lies at 1 740m; its annual rainfall is 760mm) from subtropical extremes of heat. Winters are cold, though snow is rare.




Further north and to the east, especially where a drop in altitude beyond the escarpment gives the Lowveld its name, temperatures rise: the Tropic of Capricorn slices through the extreme north. This is also where one finds the typical South African Bushveld of wildlife fame.

Those looking for an opportunity to ski in winter head for the high Drakensberg mountains that form the eastern escarpment, but the coldest place in the country is Sutherland in the western Roggeveld Mountains, with midwinter temperatures as low as -15ºC. The deep interior provides the hottest temperatures: in 1948 the mercury hit 51.7ºC in the Northern Cape Kalahari near Upington.

Average temperatures in ºC

Summer Winter

Cape Town 20 12.6

Durban 23.6 17

Johannesburg 19.4 11.1

Pretoria 22.4 12.9

Source: Lew Leppan: The South African Book of Records. Cape Town, Don Nelson, 1999.

By far South Africa's biggest neighbour is the ocean - or two oceans, which meet at the south-western corner. Its territory includes Marion and Prince Edward Islands, nearly 2 000km from Cape Town in the Atlantic Ocean.

The cold Benguela current sweeps up from the Antarctic along the Atlantic coast, laden with plankton and providing rich fishing grounds. The east coast has the north-to-south Mozambique/Agulhas current to thank for its warm waters. These two currents have a major effect on the country's climate, the ready evaporation of the eastern seas providing generous rainfall while the Benguela current retains its moisture to cause desert conditions in the west.

Several small rivers run into the sea along the coastline, but none are navigable and none provide useful natural harbours. The coastline itself, being fairly smooth, provides only one good natural harbour, at Saldanha Bay north of Cape Town. A lack of fresh water prevented major development here. Nevertheless, busy harbours now exist at Cape Town, Port Elizabeth, East London, Durban and Richard's Bay.

On dry land, going from west to east, the country shares long borders with Namibia and Botswana, touches Zimbabwe, has a longitudinal strip of border with Mozambique to the east, and lastly curves in around Swaziland before rejoining Mozambique's southern border. In the interior, nestled in the curve of the bean-shaped Free State, is the small mountainous country of Lesotho, completely surrounded by South African territory.




There are only two major rivers: the Limpopo, a stretch of which is shared with Zimbabwe, and the Orange (with its tributary, the Vaal) which runs with a variable flow across the central landscape from east to west, emptying into the Atlantic Ocean at the Namibian border. In so dry a country, dams and irrigation are extremely important: the largest dam is the Gariep on the Orange River.

4.2 The influence of topography on crop production

Site Selection

Minimizing potential production problems is essential to all farming operations. This is especially true for organic producers. One of the most effective means of reducing potential problems is through proper field site selection. Three points should be considered when selecting a field to produce vegetables: field topography, soil type, and water availability and quality.

Field topography

Topography refers to the physical characteristics of the overall field site and includes such conditions as; contour, soil depth, water and air drainage, and, the presence of rock out cropping and trees. These characteristics can have a significant influence on crop production and management. Poorly drained fields or those with low areas can become water logged during periods of excessive rain. Such conditions can enhance the incidence of diseases, reduce plant vigour and yield, and, under excessive conditions, cause plant death. Brush areas or abandoned fields and pastures can harbour insects and severe as host for plant diseases, some of which can be vectored by insects. Rock out cropping and trees within a field can become impedance to farm implements and increase difficulty of land preparation and crop establishment. Sites with slopes of 1.5 % (18" elevation change per 100') or more should be avoided to prevent excessive erosion problems. An ideal topography for vegetable production is one that is nearly flat to slightly sloping, well drained, and, free of trees, rocks and low areas. Efficiency of crop maintenance, irrigation and harvest operations is greatly enhanced in fields with this type topography (6).

Topography as a factor influencing crop production

In addition to the internal soil requirements of plants, a number of external soil requirements are of importance, such as:

Soil slope, topography and characteristics determined by micro- and macro-relief of the soil;

Occurrence of flooding as related to plant susceptibility to flooding and water-logging during the growing period, and

Soil accessibility and traffic carrying ability under defined management conditions.





MMyy NNootteess …… . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

How to overcome topography as a factor influencing crop production


MMyy NNootteess …… . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Identify and describe the influence of topography on crop production.

Topography is defined and explained.

Topography as a factor influencing crop production is explained.

Topography as a factor influencing crop production practices is evaluated.

Practices for overcoming topographical limitations to crop production are investigated and reported.




SSeessssiioonn 55

BBiioollooggiiccaall oorrggaanniissmmss wwhhiicchh iinnfflluueennccee ccrroopp pprroodduuccttiioonn..

After completing this session, you should be able to: SO 6: Identify, describe and explain the biological organisms as a factor influencing crop production.


Benefits of micro-organisms on crop production

Harmful effects of micro-organisms on crop production

Benefits of invertebrates in crop production

Harmful effects of invertebrates on crop production

How to control weeds in crop production

How to control harmful micro-organisms in crop production

5.1 BBeenneeffiittss ooff mmiiccrroo oorrggaanniissmmss oonn ccrroopp pprroodduuccttiioonn

Micro organisms

There are beneficial micro organisms and disease forming micro organisms. Some micro organisms are so small that they are only visible with the aid of a microscope. These include bacteria, fungi, and/ or viruses. Micro organisms can be very beneficial; this means that they have a good effect on your crops. There are many types of beneficial micro-organisms in soil that to decompose (breakdown) plant and animal waste turning it into organic matter. They play an important role in the recycling of dead remains and waste products. Micro-organisms also play a vital role in the environment, as they participate in the Earth's element cycles (such as the carbon cycle and nitrogen cycle).




5.2 HHaarrmmffuull eeffffeeccttss ooff mmiiccrroo--oorrggaanniissmmss

What are Fungi?

Fungi are plant-like organisms that lack chlorophyll. Fungi are one of the 5 Kingdoms of living organisms. Some fungi are useful (like mushrooms we eat), but there are also fungi that cause problems and infect plants and animals, lowering their production, growth and yield. In severe cases, fungi can cause death of parts of, or the whole plant. They multiply by releasing spores. Fungi can be yeasts or moulds.

What is a virus?

Viruses are ultra-microscopic organisms that cannot replicate without being inside a host cell.

How do viruses affect a plant?

The effect of viruses is described using the example of Leaf roll virus in vines. This virus blocks the food- and water distribution pathways of the plant. This leads to the reddening of the veins in red cultivars with the curling of the leaves in both white and red cultivars. The berries are influenced in that the sugar content is reduced.

The effects that other types of viruses such as Fan leaf and Yellow speckle virus are seen as the symptom of flattened shoots, vein clearing and consequent decrease in fruit yields.

Viruses seldom cause the plant death, but it often leads to dwarfing of the plant due to the blocked food and water transport pathways in the plant. Viruses are often spread by insects.

What are bacteria?

Individual bacteria consists of a single and can be seen with the aid of a microscope. Masses of bacteria can sometimes be seen with the naked eye as strands of a mucus like substance.

Bacteria affect the growth, yield and quality of plants and animals. Some bacteria act as pathogens and cause tetanus, typhoid fever, pneumonia, syphilis, cholera, food borne disease, leprosy and tuberculosis (TB) in animals. In plants, bacteria cause leaf spot, fire blight and wilt. Insects are often involved in the spread of bacteria.

What are nematodes?

Nematodes are microscopic, worm like soil organisms. They attack roots, peanut pods, tubers, bulbs etc. of plants. These attacks can lead to poor water and nutrient uptake (root damage) resulting in stunted plant growth or a reduction in quality (damage to tubers, pods, etc.).




5.3 BBeenneeffiittss ooff iinnvveerrtteebbrraatteess Invertebrate

Invertebrate is a term coined by Jean-Baptist Lamarck to describe any animal without a spinal column, which include insects, jellyfish, roundworms, earthworms, starfish, sea urchins, sea cucumbers, squids and snails. For the sake of this study, we will only be looking at insects, earthworms and snails.

Earthworms

Earthworms play an important role in soil . In compacted soils the earthworm actually eats its way through the soil, cutting a passage with its muscular pharynx and dragging the rest of the body along. The ingested soil is ground up, digested, and the waste deposited behind the worm. This process aerates and mixes the soil, and is constructive to nutrient uptake by vegetation. In addition, earthworms often come to the surface and graze on the higher concentrations of organic matter present there, mixing it with the mineral soil. Because a high level of organic matter is associated with soil fertility, an abundance of earthworms is beneficial to the organic gardener.

The major benefits of earthworm activities to soil fertility can be summarised as:

Biological. The earthworm is essential to composting; the process of converting dead organic matter into rich humus, a medium vital to the growth of healthy plants, and thus ensuring the continuance of the cycle of fertility. This is achieved by the worm's actions of pulling down below any organic matter deposited on the soil surface (eg, leaf fall, manure, etc) either for food or when it needs to plug its burrow. Once in the burrow, the worm will shred the leaf and partially digest it, then mingle it with the earth by saturating it with intestinal secretions.

Chemical. As well as dead organic matter, the earthworm also ingests any other soil particles that are small enough into its 'crop' wherein minute fragments of grit grind everything into a fine paste, which is then digested in the stomach. When the worm excretes this in the form of casts, which are deposited on the surface or deeper in the soil, a perfectly balanced selection of minerals and plant nutrients is made available in an accessible form. Investigations in the US show that fresh earthworm casts are 5 times richer in available nitrogen, 7 times richer in available phosphates and 11 times richer in available potash than the surrounding upper 150 mm of soil. In conditions where there is plenty of available humus, the weight of casts produced may be greater than 4.5 kg per worm per year, in itself an indicator of why it pays the gardener or farmer to keep worm populations high.

Physical. By its burrowing actions, the earthworm is of great value in keeping the soil structure open, creating a multitude of channels, which allow the processes of both aeration and drainage to occur.




It is, however, not only earthworms, which can be to the benefit of the crop, but also insects such as bees, predatory - and parasitic insects.

Bees, and some other insects also, play an important role in pollination and thus fruit formation.

Predatory- and parasitic insects act as biological control agents of harmful insects. Examples are wasps laying their eggs in the bodies or eggs of other insects. The wasp offspring then feed on the inside of the other insect bodies or eggs, killing those insects.

Ladybirds are well known predators feeding on aphids and thus play an important role in controlling aphid numbers.

Some other insects can also be parasitic on plants and can help in the biological control of weeds. A well known example is the use of cochineal on prickly pears.

5.4 HHaarrmmffuull eeffffeeccttss ooff iinnvveerrtteebbrraatteess iinn ccrroopp pprroodduuccttiioonn

♦ Snails may become serious pests when feeding on cultivated plants. A list of 49 plant species has been identified in South Africa, which are regularly predated by snails. These include:

Vegetables

cabbage, carrot, cauliflower, celery, bean, beet, brussels sprouts, lettuce, onion, peas, radish, tomato, and turnips;

Cereals barley, oats, and wheat;

Flowers

alyssum, antirrhinum, aster, balsam, carnation, candytuft, chrysanthemum, dianthus, dahlia, delphinium, hollyhock, larkspur, lilies, marguerite, mignonette, nasturtium, pansy, pentstemon, petunia, phlox, stock, sweet-pea, verbena, and zinnia;

Trees apple, apricot, citrus, peach, plum

Shrubs hibiscus, magnolia, and rose.




Insects can feed on any part of the plant. Some examples are:

Roots

Soil living weevils, worms and grubs. When feeding on the roots, it reduces the plant’s ability to take up water and nutrients. Plant growth is thus retarded and yield as well of quality of the produce are negatively affected.

Seedling stems/shoots

Weevils, worms, beetles and grubs. These can live in or above the soil. It often leads to destruction of the young seedling stem resulting in poor plant stands.

Leaves

Aphids, caterpillars, thrips, leaf miners, etc.. These insects feed on the cell contents (aphids and thrips) or the whole leaf (caterpillars and leaf miners). When they feed on the cell contents, they cause the leaf to become deformed and dysfunctional and can also spread diseases.

The caterpillars and other leaf feeders chew the soft parts of the leaves, leaving the mid-rib and veins. The leaves are thus totally destroyed, and can no longer function normally.

Stem borers

The most well know example here is the American bollworm, which is not species specific and will attack any plant. The American bollworm and other stem borers feed on the inside of the stem. Depending on the type of borer, it will feed upwards in the stem or from one side straight through the stem to the other side. Stem borers usually case the stems to break, reduce the movement of water and nutrients in the stem and can also reduce pollination as in the case of maize. In maize plants the stem borer can feed on the tassel (male flowers with pollen) which is situated at the top of the stem.

Flowers, fruits and seeds

Larvae of moths and flies (codling moth and fruit flies), aphids, scales and spider mites to name a few. These insects can partially or completely destroy the flower, fruit or seed. If the fruit or seed is the product the farmer wanted to harvest, it can lead to serious income losses. Even if they do not destroy the plant part, the visual damage it causes, can lead to a degrading of the fruit/seed with again a loss in income.




Weeds as limiting factor in crop production

Weeds are plants, which grow alongside (in the same field) our crop and interfere with the growth of our crop plants. An example is Mexican marigold (khakibush) growing in a maize field.

The weed plants compete with the crop plants for light (photosynthesis), nutrients, water and space. The weeds are strong competitors and often out compete our crop plants, which cause the crop plants to get less nutrients, water etc. This intern causes the crop plant to grow poorly and yield lower and give products with lower quality. It is therefore important to control weeds to prevent these crop losses.

Noxious (poisonous) weed seeds mixed with grains (example maize) can lower the acceptability of the grain, leading to lower grades and thus a loss in income. Weeds in cotton production is also disastrous, as weed seeds and resins produced by the weeds can come in contact with the cotton fibre, which lower the quality because the fibre is no dirty and coloured.

5.5 HHooww ttoo ccoonnttrrooll hhaarrmmffuull mmiiccrroo--oorrggaanniissmmss,, iinnvveerrtteebbrraattee aanndd wweeeeddss iinn ccrroopp pprroodduuccttiioonn

Important Note

The most economic and reliable way of dealing with weeds, pests and diseases is to anticipate

and avoid them




Keep in mind that:

All pesticides are potentially dangerous to man, animals and the environment if not applied according to the instructions on the label and handled with care.

Normal cultivation practices can often be adapted to minimise pest damage. Crops which is growing well is less prone to attacks by pests and diseases and can often resist these attacks better than weaker crops.

Insects can often facilitate in the spread of diseases and therefore insect control should also be part of the management plan to protect plants against disease attacks.

Weed management is also important in disease control, as weeds can act as host to the disease, helping it to stay alive even when the crop is not on the field.

The following guidelines should help you manage pests and diseases crops.

Cultivar selection

• Select a cultivar, which is known to have a high yield and to produce a crop of high quality under local growing conditions.

• Consider a cultivar with resistance to or acceptable tolerance of certain diseases or nematodes.

• A cultivar, which is adapted to local conditions, should yield healthy plants.

• Stay informed about the latest cultivar developments concerning disease and insect resistance or tolerance.

Field selection

• It is easier to control pests and diseases on land that is well suited to the crop.

• The soil should have a sufficient depth, a uniform texture and good drainage.

• Make sure the soil is free of nematodes. Fumigate if necessary.

• The water-holding capacity of the soil should be suitable for the crop.

• Do a soil analysis to determine nutrient deficiencies and salinity. Rectify these before planting.




• Find out which pesticides, insecticides and herbicides have been used on the land previously. Take the waiting period of the product into account and make sure that it is safe to plant.

• Consider the history of the land, such as the occurrence of weeds, pests and diseases, and apply countermeasures (management practices).

Land preparation

• Well-prepared fields and seedbeds encourage healthy plant growth.

• Break up compacted soil layers before planting.

• Do not till soil which is too wet, because this could cause compaction.

• Level the soil.

• Deep ploughing destroys certain insects, nematodes and seeds of various weeds.

Planting time

• Some diseases, insects and weeds are more prevalent during certain times of the year when conditions favour their development. Manipulating planting dates can reduce the incidence of weeds, pests and diseases. Keep in mind, however, that planting dates for crops usually allow for optimum growth during specific weather conditions.

Fertilisation

• A well-balanced fertilisation programme will contribute to vigorous, healthy growth and high yields of good quality.

• Nutrient deficiencies and imbalances could cause poor growth, making the plants more prone to attacks by pests.

• Have the soil analysed and apply fertiliser as recommended.

Irrigation

• Irrigation scheduling is very important. An over or undersupply of water causes poor growth and resistance to pests and diseases.

• Apply sprinkler irrigation from planting to the seedling stage and then switch to furrow irrigation until harvest.

• When using sprinklers, do not apply more water than




can infiltrate the soil. Avoid runoff and the formation of surface puddles.

• Soil splashing onto leaves during sprinkler irrigation can spread diseases.

• Sprinkler irrigation on older plants may increase disease problems; furrow irrigation is therefore preferred.

Chemicals – insecticides, pesticides and herbicides

• Chemicals, when applied properly, provide convenient and economical protection against weeds, pest and diseases.

• Careless and excessive use, however, could result in poor control and crop damage and pose a threat to human health and the environment.

• Use chemicals only when necessary.

• The choice of a product depends on its efficacy, the degree of control required and the economic implications.

• Repeated application of the same pesticide can cause pests to become resistant.

• Always read the label before applying any chemical and follow the instructions.

Sanitation

• Dispose of residual plant material as soon as possible. This may be done by chopping the plants and deep ploughing the residue or even burning it.

• Adequate control of annual weeds, especially before seeding, will reduce weed competition and crop pests and diseases.

• To prevent the spread of nematodes it is important not to introduce contaminated soil into your land via equipment, transplants, manure or runoff.

• Use only disease-free seed for planting.

• Remove and destroy infested plant material whenever possible.

Rotation

• The populations of certain weeds, pests and diseases can be limited by planting lands with crops, which do not promote their development.

• Rotating crops restricts the use of a wider range of herbicides, e.g. you cannot plant broad-leaf crops such as sunflower, beans, potatoes, etc. after using atrazine (a broad leaf herbicide) on maize.




Please complete Activity 13 & 14 in your learner workbook

MMyy NNootteess …… . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Identify, describe and explain the biological organisms as a factor influencing crop production.

The beneficial effects of micro-organisms on crop production are identified and described.

The harmful effects of micro-organisms in crop production are identified and described.

Control options of harmful micro-organisms in crop production are identified and described.

The beneficial effects of invertebrates in crop production are identified and described.

The harmful effects of invertebrates on crop production are identified and described.

Control options for invertebrates in crop production are identified and described.

Weeds as a limiting factor in crop production is explained.

Control options for weeds in crop production are discussed.




SSeessssiioonn 66

TThhee eeffffeeccttss ooff ccrroopp pprroodduuccttiioonn oonn tthhee ssuussttaaiinnaabbiilliittyy ooff tthhee eennvviirroonnmmeenntt After completing this session, you should be able to: SO 7: Assess the effects of crop production practices on the sustainability of the environment.


What is sustainability?

Which existing crop production practices are there?

Crop production practices that enhance agricultural sustainability

Crop production practices that have a negative impact on the sustainability of the environment

6.1 What is sustainability?

Sustainability: The ability to provide for the needs of the world's current population without damaging the ability of future generations to provide for themselves. When a process is sustainable, it can be carried out over and over without negative environmental effects or impossibly high costs to anyone involved.




6.2 CCrroopp pprroodduuccttiioonn pprraaccttiicceess

Sustainable management is an introduction to issues surrounding today’s agricultural system and what is happening with our food, in particular, the meat supply.

Rather than feeling hopeless over the problems with our food, research and learning has been created to celebrate the possibilities and realities of this growing consumer movement. After learning about the problems we’re all confronted with, you’ll be introduced to organizations, people and programs that are changing the way we think about food.

Sustainable agriculture is more a way of life than a law or regulation. Each step you take benefits both you and your family, and helps preserve and protect the planet for future generations.

Sustainable agriculture is a way of raising food that is healthy for consumers and animals, does not harm the environment, is humane for workers and animals, provides a fair wage to the farmer, and supports and enhances rural communities.


MMyy NNootteess …… . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.3 CCrroopp pprroodduuccttiioonn pprraaccttiicceess tthhaatt eennhhaanncceeaaggrriiccuullttuurraall ssuussttaaiinnaabbiilliittyy

Characteristics of this type of agricultural actions for sustainability include:

Conservation and preservation

What is taken out of the environment is put back in, so land and resources such as water, soil and air can be replenished and are available to future generations. The waste from sustainable farming stays within the farm’s ecosystem and cannot cause build-up or pollution. In addition, sustainable agriculture seeks to minimize transportation costs and fossil fuel use, and is as locally-based as possible.




Biodiversity Farms raise different types of plants and animals, which are rotated around the fields to enrich the soil and help prevent disease and pest outbreaks. Chemical pesticides are used minimally and only when necessary; many sustainable farms do not use any form of chemicals.

Animal welfare Animals are treated humanely and with respect, and are well cared for. They are permitted to carry out their natural behaviours, such as grazing, rooting or pecking, and are fed a natural diet appropriate for their species.

Economically viable

Farmers are paid a fair wage and are not dependent on subsidies from the government. Sustainable farmers help strengthen rural communities.

Socially just Workers are treated fairly and paid competitive wages and benefits. They work in a safe environment and are offered proper living conditions and food.

In addition to the variety of species and habitats found on Earth (biodiversity), sustainability also takes humans into account.

Remember…why grass species are so important to Mankind: The Grass Family contains plants such as sorghum, maize, rice, millet etc, as well as large plants such as 'bamboo'. It is not surprising, therefore, that the bulk of the world's food supply comes from this family of plants. Meat comes from stock that have fed on grasses. Eggs come from poultry that have fed on grain that comes from 'grass'. Butter and cheese comes from milk, which comes from stock that has fed on grass, or grain from 'grass'. Sugar comes from ‘cane’, which is a grass. There is hardly any organic food item that doesn't originate from plants, with by far the greatest bulk of it originating from grass.

6.4 CCrroopp pprroodduuccttiioonn pprraaccttiicceess tthhaatt hhaavvee aa nneeggaattiivvee iimmppaacctt oonn tthhee ssuussttaaiinnaabbiilliittyy ooff tthhee eennvviirroonnmmeenntt

Low-external-input agricultural systems are generally located on dry lands, wetlands, uplands, savannahs, swamps, near-deserts, mountains and hills, and forests. Farming systems in these areas are complex and diverse, but agricultural yields are low, and rural livelihoods are often dependent on wild resources as well as agricultural produce. Farms are remote from markets




and infrastructure; they are located on fragile or problem soils that are liable to degradation.

Stalinization is the concentration of abnormally high levels of salts, for example, sodium, in soils due to evaporation. It frequently occurs in association with irrigation and leads to plant death of and loss of soil structure.

High usage rate of pesticides may lead contamination of soil, water and other environmental compartments. This leads to serious damage to the natural systems.

The loss of organic matter due to erosion and oxidation degrades the soil and in particular its value as a crop-growing medium. The loss of organic matter decreases the stability of soil aggregates, which under the impact of rainfall may then break up. This process may lead to the formation of soil crusts, which reduce infiltration of water into the soil and increase the likelihood of run-off and water erosion occurring. Soil crusts also inhibit the germination of seeds. In monoculture systems where soil organic matter is not preserved, erosion is promoted.

The loss of soil structure occurs when organic matter is lost, when compaction occurs due to the use of agricultural machinery and cultivation in wet weather, or dispersion of soil materials in the subsoil.




The concept of sustainability is explained and defined.

Existing crop production practices are identified.

Crop production practices that enhance agricultural sustainability are identified and explained.

Crop production practices that have a negative impact on the sustainability of the environment are identified and explained.




GGlloossssaarryy Term Description

Bacteria Bacteria are single celled organisms that can only be studied with the aid of a microscope.

Beneficial Something that is to the advantage of the crop. The opposite of a pest.

Clay particles Are the smallest sized soil particles (less then 0.002 mm in diameter), and they feel "sticky" and they are hard to squeeze. Very fine soil particles.

Climate Climate is the average weather conditions of a place, usually measured over one year.

Crop hygiene Keeping crops clean from diseases.

Decompose

The process whereby soil microbes and animals eat organic material, breaking it down into smaller and smaller pieces. This process recycles the nutrients found in the organic material, making the nutrients available for further plant growth.

Diseases Bacterial, fungal and virus organisms attacking the crop plant, preventing the crop plant from growing and producing optimally

Erode To break down into smaller pieces.

Evaporation It is the process whereby atoms or molecules in a liqud state gain sufficient energy to enter the gaseous state. It's the opposite process of condensation.

Fungi Fungi are microscopic thread-like, saprophytic or parasitic organisms. It can usually clearly be observed without a microscope.

Fungicide Chemical compounds (synthetic as well as natural products) used in managing fungal diseases

Herbicide Chemical compounds (synthetic as well as natural products) used in managing weeds

Hydroponics

Is crop production with mineral nutrient solutions instead of soil containing silt and clay. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as sand and gravel.




Term Description

Insecticide Chemical compounds (synthetic as well as natural products) used in managing insects

Invertebrate

Invertebrate is a term coined by Jean-Baptiste Lamarckto describe any animal without a spinal column, which include insects, jellyfish, roundworms, earthworms, starfish, sea urchins, sea cucumbers, squids and snails.

Micro-organism An organism so small, that it can often only be seen under a microscope

Mulching A layer of dead plant material on the surface of the soil to protect the soil against water and wind erosion.

Nematodes Nematodes are microscopic, worm like organisms living in the soil

Organic Derived from living organisms such as plants, animals, fungi or bacteria.

Parasitic An organism which life in close association with another organism, using it as food source without killing it. Exp a tick on a dog.

Ped A naturally formed unit of soil particles.

Pest An organism which causes damage to the crop. This can include insects and insect related organisms, rodents, farm animals, birds etc.

Pesticides Chemical compounds (synthetic as well as natural products) used in managing pests

pH A measure of how acidic or basic things are and is measured using a pH scale between 0 to 14, with acidic things having a pH between 0-7 and basic things having a pH from 7 to 14.

Photosynthesis

Is a fundamental biochemical process in which higher plants, algaei and some bacteria convert the energy of sunglight into chemical energy. The chemical energy is then used to fix carbon into simple sugars that are converted to glucose, the major food molecule of the cell.

Pollen Fine yellow dust produced by flower which represent the male sex cells of the plant

Pollination The process whereby the pollen comes in contact and adhere to a receptive stigma (female part of flower).

Predator An organism which capture other another organism, killing and feeding on it.

Produce That which will be harvested from the crop. Example tomato fruit, maize kernels, mango fruits, sunflower seeds etc.




Term Description

Sand Particles Are the largest soil particles (0.05 to 2.0 mm in diameter) and they feel "gritty." Very coarse soil particles.

Silt Particles Are medium sized soil particles (more than 0.002 mm but less than 0.05 mm in diameter), and they feel soft, silky or "floury."

Soil aggregate A single mass or cluster of soil particles

Soil Consistency The resistance to deformation or rupture of a soil mass (ped or aggregate)

Soil drainage The rate and extent of water movement in the soil

Soil structure Soil structure is the shape of the aggregates or peds and their arrangement in the profile, based on its physical and chemical properties.

Soil Texture The relative proportions of sand, silt and clay particles in the soil, thus how coarse or fine a soil is.

Sustainability

The ability to provide for the needs of the world's current population without damaging the ability of future generations to provide for themselves. When a process is sustainable, it can be carried out over and over without negative environmental effects or impossibly high costs to anyone involved.

Topography Is derived from the Greek "topos" (place) and "graphein" (to draw), and refers to the lie of the land, and is usually expressed in terms of the elevation, slope, and orientation of terrain features.

Transpiration Is the evaporation of water from aerial parts of plants, especially leaves but also stems, flowers and fruits.

Virus

They appear as rods or spheres when viewed under a microscope and consist of a nucleic acid rod (DNA) surrounded by a protein coat. On entering the cell, the virus takes over the functions of the cell nucleus to produce many more particles that spread to adjacent cells.

Water holding capacity

The soil’s ability to stay wet after irrigation/rainfall

Weather Weather is the day-to-day condition of the atmosphere. This includes temperature, precipitation (rainfall, snow, hail), humidity and wind.

Weed Any plant which prevents the crop plant from growing and producing optimally.




BBiibblliiooggrraapphhyy BBooookkss::

Encyclopaedia Brittanica – South African Version

Wikepedia – International Version

Guide to Grasses of South Africa by Frits van Oudtshoorn

Veld Management in South Africa, by Neil Tainton

People’s farming handbook by various authors

A glossary of Soil Science by Hennie v.H. van der Watt and Theo H. van Rooyen

South African plant disease control handbook by Sue Esterhuysen, Thelma Trench and Debbi Wilkinson

WWoorrlldd WWiiddee WWeebb::

wordnet.princeton.edu/perl/webwn

wordnet.princeton.edu/perl/webwn

http://en.wikipedia.org/wiki/Calculator#A_basic_calculator

www.en.wikipedia.org/wiki

http://www.mathwords.com/b.htm

enchantedlearning.com

http://www.safrica.info/doing_business/economy/key_sectors/542547.htm

TTeerrmmss && CCoonnddiittiioonnss This material was developed with public funding and for that reason this material is available at no charge from the AgriSETA website (www.agriseta.co.za). Users are free to produce and adapt this material to the maximum benefit of the learner. No user is allowed to sell this material whatsoever.




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All qualifications and unit standards registered on the National Qualifications Framework are public property. Thus the only payment that can be made for them is for service and reproduction. It is illegal to sell this material for profit. If the material is reproduced or quoted, the South African Qualifications Authority (SAQA) should be acknowledged as the source.

SOUTH AFRICAN QUALIFICATIONS AUTHORITY

REGISTERED UNIT STANDARD:


SAQA US ID UNIT STANDARD TITLE

13355 Demonstrate an understanding of the physical and biological environment and its relationship to sustainable crop production

SGB NAME NSB PROVIDER NAME

SGB Primary Agriculture

NSB 01-Agriculture and Nature Conservation

FIELD SUBFIELD

Agriculture and Nature Conservation Primary Agriculture

ABET BAND UNIT STANDARD TYPE NQF LEVEL CREDITS

ABET Level 4 Regular Level 1 4

REGISTRATION STATUS

REGISTRATION START DATE REGISTRATION END DATE

SAQA DECISION NUMBER

Registered 2000-12-06 2003-12-06 SAQA 1033/00

PURPOSE OF THE UNIT STANDARD

A candidate credited with this unit standard will be capable of: identifying and describing the nature of soil; soil as a factor in agricultural production; climatic factors influencing crop production and their practical implications; the importance of water as a factor in agricultural production; the influence of topography on agricultural production; biological organisms as a factor influencing crop production and assessing the effects of crop production practices on the sustainability of the environment.

LEARNING ASSUMED TO BE IN PLACE AND RECOGNITION OF PRIOR LEARNING

Open

Specific Outcomes and Assessment Criteria:

SPECIFIC OUTCOME 1

Identify and describe the nature of soil.

OUTCOME RANGE

Physical properties of soil

ASSESSMENT CRITERIA

ASSESSMENT CRITERION 1

1. The principle that soil is a product of its environment is described.


2. Soil components are identified.


ASSESSMENT CRITERION RANGE

sand; loam; clay


3. Soil texture is identified.


4. Soil texture is described.


5. Soil structure is identified.


structured and structureless soil

SPECIFIC OUTCOME 2


ASSESSMENT CRITERIA


1. Reasons why soil is a factor in crop production are provided.


2. Factors affecting the role of soil in crop production are described.


3. The concept of soil productivity is explained.


4. Factors that improve soil productivity and crop production are investigated.


5. Soil limitations in crop production are identified.


6. Ways to overcome soil limitations in crop production are explained and justified.

SPECIFIC OUTCOME 3


ASSESSMENT CRITERIA


1. Climatic factors influencing crop production are identified.



2. Climatic factors influencing crop production are described.


3. The influence of climatic factors on crop production is explained.


4. Crop production practices that can be adapted to climatic factors are investigated and reported.

SPECIFIC OUTCOME 4

Identify and describe the importance of water as a factor in crop production.

ASSESSMENT CRITERIA


1. Sources of water are identified.


Source, quality and quantity


2. The role of water in crop production is explained.


3. The principle of water as a finite resource in crop production is explained.


4. The optimal use of water resources in crop production is explained.


5. Conclusions regarding the significance of water in crop production are drawn.

SPECIFIC OUTCOME 5

Identify and describe the influence of topography on crop production.

ASSESSMENT CRITERIA


1. Topography is defined and explained.


2. Topography as a factor influencing crop production is explained.


3. Topography as a factor influencing crop production practices is evaluated.



4. Practices for overcoming topographical limitations to crop production are investigated and reported.

SPECIFIC OUTCOME 6

Identify, describe and explain the biological organisms as a factor influencing crop production.

ASSESSMENT CRITERIA


1. The beneficial effects of micro-organisms on crop production are identified and described.


2. The harmful effects of micro-organisms in crop production are identified and described.


3. Control options of harmful micro-organisms in crop production are identified and described.


4. The beneficial effects of invertebrates in crop production are identified and described.


5. The harmful effects of invertebrates on crop production are identified and described.


6. Control options for invertebrates in crop production are identified and described.


7. Weeds as a limiting factor in crop production is explained.


8. Control options for weeds in crop production are discussed.

SPECIFIC OUTCOME 7


ASSESSMENT CRITERIA


1. The concept of sustainability is explained and defined.


2. Existing crop production practices are identified.


3. Crop production practices that enhance agricultural sustainability are identified and explained.


4. Crop production practices that have a negative impact on the sustainability of the environment are identified and explained.


UNIT STANDARD ACCREDITATION AND MODERATION OPTIONS

UNIT STANDARD ESSENTIAL EMBEDDED KNOWLEDGE

Examples of crop production practices which enhance environmental sustainabililty include mulching, crop rotation, stubble mulching, green manure, composting, etc. This list is not all inclusive.

Critical Cross-field Outcomes (CCFO):

UNIT STANDARD CCFO IDENTIFYING

Identify and solve problems in which responses display that responsible decisions using critical and creative thinking have been made;

UNIT STANDARD CCFO WORKING

Work effectively with others as a member of a team, group organisation and community;

UNIT STANDARD CCFO ORGANIZING

Organise and manage oneself and one`s activities responsibly and effectively;

UNIT STANDARD CCFO COLLECTING

Collect, analyse, organise and critically evaluate information;

UNIT STANDARD CCFO COMMUNICATING

Communicate effectively using visual, mathematical and/or language skills in the modes of oral and/or written presentation;

UNIT STANDARD CCFO DEMONSTRATING

Demonstrate an understanding of the world as a set of related systems by recognising that problem-solving contexts do not exist in isolation.

UNIT STANDARD NOTES

Learners should be encouraged to work in groups when identifying and observing the factors influencing crop production. Developmental Outcomes: This unit standard supports the following developmental outcomes: 1. Reflecting on and exploring a variety of strategies to learn more effectively; 2. Participating as responsible citizens in the life of local, national and global communities; 3. Being culturally and aesthetically sensitive across a range of social contexts; 4. Exploring education and career opportunities; and 5. Developing entrepreneurial opportunities.

All qualifications and unit standards registered on the National Qualifications Framework are public property. Thus the only payment that can be made for them is for service and reproduction. It is illegal to sell this material for profit. If the material is reproduced or quoted, the South African Qualifications Authority (SAQA) should be acknowledged as the source.

Documents

13355 Learner Guide web 15Sept06 - AgriSeta · 2006. 10. 12. · Dear Learner - This Learner Guide contains all the information to acquire all the knowledge and skills leading to