Animal, Plant & Soil Science E6-2 Growing Corn

Interest Approach

Display an ear of dent corn, an ear of popcorn, and an ear of Indian corn. Ask the students whether they think all three were grown in the same way. If they think so, ask them what practices must be followed to produce corn. If they think they are grown differently, ask what production practices are different.

Objectives 1 Identify and describe the components of a corn seed, and

explain the production practices involved in the seedbed preparation and planting of corn.

2 Compare and contrast the characteristics of corn varieties, and examine the corn hybrid selection process.

3 Determine the nutrient requirements, and calculate the proper amount of fertilizer to apply in various situations.

4 Examine the developmental stages of a corn plant, and determine factors that affect each stage.

5 Identify specific weeds, insects, nematodes, and diseases that affect corn, and describe management practices that can be used to prevent or minimize damage.

6 Determine the harvest readiness of corn, calculate yield estimates, and determine harvest loss.

7 Estimate the fixed and variable costs to produce an acre of corn, estimate the income from an acre of corn, and determine factors that affect the profitability of corn production.

8 Identify the equipment that is typically used in corn production, and describe how it is used.

Terms aflatoxin cost per acre cost per bushel crown embryo endosperm fixed costs growing degree day

(GDD) hilum

hybrid kernel lodging plant population return per acre seed coat standability variable costs variety

What are the components of a corn seed? What are theproduction practices involved in the seedbed preparation and planting of corn?

I. Corn seed is composed of several parts, and successful corn production depends on cultural practices, which are the procedures used in producing a crop (e.g., selecting a variety, planting, fertilizing, controlling pests, and harvesting). These practices vary with the crop being produced.

What are the components of a corn seed? What are theproduction practices involved in the seedbed preparation and planting of corn? A. Corn is produced through sexual means. Typically,

corn seeds are planted at the proper time in prepared soil.

1. The kernel is the part of the individual grain within the seed coat. Corn kernels are enclosed in a seed coat, which is the outer covering of a seed. Inside the seed are the embryo (undeveloped seedling) and the endosperm.

2. Corn kernels contain two types of endosperm: starchy and flinty. The endosperm is the food for the seedling inside the seed. Starchy endosperm is soft, and flinty endosperm is hard. The amount of each type determines how the corn can be used.

3. The ends of the corn kernel are the crown and the hilum. The crown is the outer end of the corn kernel, and the hilum is the point of attachment on the seed.


B. Grain crops, such as corn, require moderate rainfall, frost-free temperatures, warm weather, and sunshine. Medium-textured soils will help to provide optimum corn yields.

1. Corn is a warm season crop and germination is best when temperatures are warm.

2. Planting should occur after the danger of frost has passed.

3. A rule of thumb is to plant corn at a depth of two inches after soil temperatures are above 50°F (10°C).


C. Corn requires fertile soil for growth. Specific nutrient requirements vary by cultivar, but the optimum soil pH is between 5.0 and 8.0.

What are the components of a corn seed? What are theproduction practices involved in the seedbed preparation and planting of corn? D. Corn should be planted in a prepared seedbed,

which can be prepared by plowing with a chisel or moldboard plow followed by a disk harrow or do-all. Plowing and disking reduces soil clods and prepares a fine seedbed.

1. No-tillage planting is a widely accepted practice. In this case, corn seeds are slightly deeper, but because of crop residue, less soil covers the seed.

2. Corn is planted in rows 20 to 40 inches apart and 1 to 2 inches deep. Yields per acre increase with narrower rows. A planter is used to open the seed drill and place the seed.


E. The number of plants grown per acre or plant population is important. The desired plant population for corn is typically 24,000 to 32,000 plants per acre. Planters can be set to achieve a desired plant population.

1. Plant population is easy to calculate. First, determine the row width. Divide the width in feet into 43,560 (square feet per acre) to determine the total length of all rows in an acre. Divide the number of plants into the row length to calculate the distance between the seed.

How do the characteristics of corn varieties compare? How are corn hybrids selected? II. In the United States, all varieties

of corn sold for commercial grain production are hybrids. A variety is a cultivated plant within a species that shows significant difference from other plants in the species and retains its features when reproduced. A hybrid is an offspring from genetically different parents. Hundreds of hybrids are available for planting; many are bred for use in local areas.

How do the characteristics of corn varieties compare? How are corn hybrids selected?

A. A variety should be chosen that matures according to the date of the first local frost. Days to maturity range from 50 to 330 days.


B. Corn varieties are selected by height and number of ears per stalk. Corn plants are commonly 6- to 8-feet tall, but the plants can grow from 2- to 20-feet tall. On average, corn plants will produce 1 to 3 ears.

How do the characteristics of corn varieties compare? How are corn hybrids selected? C. The corn variety should be

selected based on the climate of the area. The optimum temperatures for corn growth are 70 to 86°F (21.1 to 30°C). Adequate rainfall is also important. Frosts are detrimental to the production of a quality corn crop. Early frosts cause damage to the plant by damaging leaves and delaying growth. Late season frosts may cause more damage than spring frosts by causing severe leaf injury or death.

How do the characteristics of corn varieties compare? How are corn hybrids selected? D. Corn varieties are selected based on

growing degree days. A growing degree day (GDD) is a measure of the temperature requirements for best corn growth. The GDD is calculated by adding the maximum temperature and the minimum temperature in a day, dividing by two, and subtracting 50. Because corn grows very little at 50°F (10°C) or cooler temperatures, 50 is a constant. The maximum temperature used is 86, because temperatures above 86°F (30°C) do not increase the rate of growth. Temperatures above 86 are counted as 86.

How do the characteristics of corn varieties compare? How are corn hybrids selected? E. Corn standability is a

consideration in selecting corn varieties. Standability can be equated to the percentage of stems that grow erect and resist lodging. Some varieties have stronger stems and are less susceptible to lodging (falling over or suffering from a broken stem). Corn plants that fall over or break are difficult to harvest. The plant population, weather conditions, excess nitrogen, insect issues, and disease problems can affect standability.


F. Resistance to insect pests and diseases is another important consideration when selecting varieties. Resistant varieties can provide savings on pest management costs and produce better yields than less resistant varieties.

What are the nutrient requirements? How is the proper amount of fertilizer to apply in various situations calculated?

III. A healthy corn plant requires a good fertilizer due to the nutrient requirements.

A. Corn requires more nutrients than most other crops. To yield 150 bushels per acre, a corn crop will require 170 pounds of N, 35 pounds of P2O5, and 175 pounds of K2O.

What are the nutrient requirements? How is the proper amount of fertilizer to apply in various situations calculated?

B. Proper calculation of nitrogen fertilizers is essential due to rising costs for nitrogen and water quality concerns.

1. Research has shown that modern high-yielding corn hybrids should be given no more than 1.2 pounds of nitrogen per bushel.

2. Nitrogen fertilization also should be based on expected crop yields minus credits for residual soil nitrates, estimated nitrogen mineralized from soil organic matter, previous legume crop residues, manure or other organic wastes, and nitrogen present in irrigation water.

What are the developmental stages of a corn plant? What factors affect each stage?

IV. Corn development is divided into vegetative (V) and reproductive (R) stages. The vegetative growth stages come before the reproductive stages, and different factors affect each stage.

What are the developmental stages of a corn plant? What factors affect each stage? A. Subdivisions of the vegetative stages for

corn are designated numerically.

1. VE represents the emergence of the plant. 2. V1 is the first fully expanded leaf with the

leaf collar. 3. V2 is the second fully expanded leaf with

the leaf collars. 4. Each successive leaf development and leaf

collar is given a V and a number. 5. The last vegetative stage (VT) occurs when

the last tassel branch is fully visible.

What are the developmental stages of a corn plant? What factors affect each stage? B. Reproductive (R) stages are designated R1 through

R6.

1. R1 (silking) occurs when silks are visible outside of husks.

2. R2 (blister) is when the liquid in the kernel is the color and consistency of a blister. The endosperm turns white and becomes thicker as solid starch is deposited.

3. R3 is designated as the milk stage. 4. R4 is designated as the dough stage. 5. During R5, a dent forms at the tip as the center of the

kernel collapses because of shrinkage. After R5, a milk line forms and marks the layer between solid and liquid starch in the endosperm.

6. At R6, physiological maturity occurs when kernels have obtained their maximum dry weight and an abscission layer (black or brown) forms near the bottom of the kernel.

What are specific weeds, insects, nematodes, and diseases that affect corn? What management practices can be used to prevent or minimize damage?

V. Common corn pests include weeds, insects, nematodes, and diseases. Each of these pests includes several types, but certain management practices can be utilized to prevent or minimize yield loss.


A. Weeds are generally controlled through cultivation practices and the use of herbicides. Denser plant populations also reduce weed problems.


B. Corn is vulnerable to a number of insect pests, including bud worms and ear worms.

1. Corn earworm, fall armyworm, European corn borer, and cornstalk borers boar into the whorl, stalks, or ear. Wireworms and rootworms feed on seeds, roots, and the lower stems. These insect larvae can cause significant damage to a crop.

2. Corn root aphids, corn leaf aphids, chinch bugs, and mites pierce and suck sap from corn plants.

3. Insect pests are controlled by cultural, biological, mechanical, and chemical means.


C. Many nematode species affect corn plant health. Two management strategies are available if it is determined that the corn crop is being damaged by corn nematodes. Neither option minimizes damage to the current corn crop. However, both may be useful in reducing the potential for damage to future corn crops.

1. Farmers may produce nonhost crops.

2. Nematicides also may be used.


D. Many diseases of corn exist. Some common corn diseases include Stewart’s wilt, stalk rots, leaf blights and spots, and common smut. Most of the diseases are caused by fungi.

1. Planting resistant varieties can help reduce disease problems.

2. Certain cultural practices also can assist in reducing disease problems. Cultural practices are the procedures used in producing a crop; they include selecting a variety, planting, fertilizing, controlling pests, and harvesting. Irrigation is also considered a cultural practice.

How is the harvest readiness of corn determined? How are yield estimates calculated? How is harvest loss determined?

VI. Corn harvesting should be timed for maximum yield. Farmers use specific methods to determine corn readiness, calculate yield estimates, and determine harvest loss.

How is the harvest readiness of corn determined? How are yield estimates calculated? How is harvest loss determined? A. Grain corn should be harvested at 20 to

28 percent moisture, and corn should be dried to approximately 15.5 percent.

1. Higher moisture corn requires increased artificial drying.

2. Corn in more humid areas may need to be dried to 11 percent. The increased drying should help avoid aflatoxin buildup. An aflatoxin is a highly poisonous substance in grain caused by the fungi Aspergillus florus. Aflatoxins in animal feed can cause death.

How is the harvest readiness of corn determined? How are yield estimates calculated? How is harvest loss determined? B. Estimating yields before the corn is

harvested helps when making plans for storage and marketing. Estimating corn yields is accomplished by counting the number of ears per acre and the number of kernels per ear and then multiplying these two numbers to get an estimate of the number of kernels per acre. It is followed by dividing by an average number of kernels in a normal bushel to get the yield in bushels per acre. Corn yields can be estimated about two weeks after the end of pollination. By that time, the kernel number is fixed. The following steps are suggested.


1. Planning in advance is necessary before entering a field to take a sample. For instance, the plan may be to go 20 rows from the edge of the field and 40 paces from the end of the field. There is a tendency to stop where the crop looks better than average, but it is necessary to stop exactly where planned.

2. For each field to be estimated, a length of row equal to 1/1000th acre should be measured off. The row length required to equal 1/1000 acre depends on the width (For example, a row width of 20 inches would be equal to 26 feet and 1 inch. Additionally, a row width of 28 inches would be equal to 18 feet and 8 inches; a row width of 30 inches would be equal to 17 feet and 5 inches, etc.). The number of ears (not stalks) in that distance should be counted.


3. The number of ears on the plants in the 1/1000th acre of row that are harvestable should be counted and recorded. Then three ears should be taken from the row that was counted. Taking only good ears should be avoided by removing the third, sixth, and tenth ears in the length of the row. Ears with so few kernels that they were not included in the ear count should not be taken.

4. The number of complete kernel rows per ear and the average number of kernels per row should be recorded. Then each ear’s row number should be multiplied by its number of kernels per row to calculate the total number of kernels per ear.


5. The average number of kernels per ear should be calculated by summing the values for all the sampled ears and dividing by the number of ears.

6. The yield for each site should be estimated by multiplying the ear number by the average number of kernels per ear. Divide that result by 90. The value of “90” represents the average number of kernels (90,000) in a bushel of corn.

How is the harvest readiness of corn determined? How are yield estimates calculated? How is harvest loss determined? C. Corn left behind when the field is combined

represents a harvest loss and a loss of profits. There will always be some harvest loss, but measures can be taken to limit the losses.

1. The total ear loss can be determined by counting the number of full-size ears, or the equivalent, in a 1/100-acre area (Table 1). Each full-size ear represents approximately 1 bushel per acre loss.

2. To measure kernel loss, the loose kernels on the ground and those still attached to threshed cobs in a 10-square-foot area for each row behind the combine can be counted. The area should have width equal to the planted row width (Table 2). The presence of two kernels per square foot equals a 1 bushel per acre loss.

How is the harvest readiness of corn determined? How are yield estimates calculated? How is harvest loss determined? 3. Manufacturer’s settings should be followed

to minimize losses. The proper combine setting maximizes income by reducing harvest loss and reducing volunteer corn issues the following growing season. The deck plates or snapping rolls should be adjusted to match the size of the ear and stalks, which helps prevent shelling on the ear and slipping ears through the front of the machine.


How are fixed and variable production costs estimated for an acre of corn? How is the income from an acre of corn estimated? What are the factors that affect the profitability of corn production?

VII. A corn enterprise must be profitable to justify the cost and effort to produce a crop. Certain steps can be followed to estimate production costs and corn income, but additional factors that affect profitability also should be considered.

How are fixed and variable production costs estimated for an acre of corn? How is the income from an acre of corn estimated? What are the factors that affect the profitability of corn production? A. Costs and returns for each acre under production

can be estimated.

1. Cost per acre is the total of seed, fertilizer, chemical, drying, interest, equipment, and land costs.

2. Cost per bushel is the cost per acre divided by the yield.

3. Return per acre is the quantity of yield multiplied by the price; then cost per acre is subtracted. Return per acre is the amount of money left over to pay for other items not easily accounted for, such as overhead, utilities, improvements, management, building costs, taxes, etc.

How are fixed and variable production costs estimated for an acre of corn? How is the income from an acre of corn estimated? What are the factors that affect the profitability of corn production? B. The profitability of a crop can be determined by following a

number of steps.

1. The first step is to estimate the total corn yield and the expected output price. The estimated yields and prices should be based on normal conditions.

2. The second step is to estimate variable costs. Variable costs are costs that vary with the amount of product produced. These are the out-of-pocket costs that must be incurred if the enterprise is produced or grown. Some examples of variable costs include seed, fertilizer, hired labor, repairs, supplies, and fuel.

3. The third step is to evaluate fixed costs, which remain about the same no matter how much is produced. Some examples of fixed costs are insurance, taxes, and depreciation.

4. The last step is calculating net receipts, which represent the income that is left for the farmer and family to live on, pay debt, invest, or save.

How are fixed and variable production costs estimated for an acre of corn? How is the income from an acre of corn estimated? What are the factors that affect the profitability of corn production?

C. The profitability of corn depends on many factors. Economic factors, such as commodity prices and input costs, are among the most important. Cultural practices including crop rotation, the selection of varieties well suited for environmental conditions, harvest efficiency, and pest management also play an important role in determining profitability.

What equipment is typically used in corn production, and how is it used?

VIII. The large scale production of corn in the United States depends on the use of equipment and technology.

A. Tillage implements are used for multiple purposes. For example, tillage equipment is used for seedbed preparation and to incorporate residues, fertilizers, etc. into the soil. Weeds also can be controlled with tillage equipment. In some cases, tillage equipment is used to roughen the soil surface to slow the velocity of the wind and, therefore, to reduce erosion.


B. Planters are used to place seeds in the soil in rows usually 20 to 40 inches apart.

C. Cultivators come in a variety of shapes, sizes, and attachments. They are used to keep the area between the rows clean and free of weeds.

D. Spray equipment is typically used to apply chemicals, such as pesticides.


E. Corn can be harvested with a picker or combine. A combine is fitted with a corn head, which is specifically designed to harvest corn. It performs the tasks of harvesting, threshing, and cleaning the grain.

F. Farm tractors are used for many purposes, including the pulling of implements and providing power to attachments through the power take-off (PTO).


G. Grain storage structures hold grain until it is ready for market.


H. A global positioning system (GPS) provides the farmer with the technological means to practice precision agriculture.

REVIEW 1. What are the components of a corn seed? What are the

production practices involved in the seedbed preparation and planting of corn?

2. How do the characteristics of corn varieties compare? How are corn hybrids selected?

3. What are the nutrient requirements? How is the proper amount of fertilizer to apply in various situations calculated?

4. What are the developmental stages of a corn plant? What factors affect each stage?

5. What are specific weeds, insects, nematodes, and diseases that affect corn? What management practices can be used to prevent or minimize damage?

6. How is the harvest readiness of corn determined? How are yield estimates calculated? How is harvest loss determined?

7. How are fixed and variable production costs estimated for an acre of corn? How is the income from an acre of corn estimated? What are the factors that affect the profitability of corn production?

8. What equipment is typically used in corn production, and how is it used?

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Animal, Plant & Soil Science E6-2 Growing Corn