Recycling of crop residues for

improved soil nutrient status

and farm income

Dr BASUDEV BEHERA

PROFESSOR & HEAD

DEPARTMENT OF AGRONOMY

CA, OUAT, BHUBANESWAR

05.02.2018

Crop residues• Crop residues are parts of the plants left

in the field after crops have been harvested and threshed.

• In India there are 500-550 million tones (Mt) of crop residues are produces annually

• Gadde et al. (2009) estimated that the • Gadde et al. (2009) estimated that the burning of rice straw contributed 0.05% of the total amount of greenhouse gas (GHG’s) emissions in India, which not only lead to loss of huge biomass, i.e. organic carbon, plant nutrients, but also cause adverse effect on soil properties as well as soil flora and fauna.

Crop residue – Types

a) Crop wastes of cereals, pulses,

oilseeds(Rice, wheat, jowar, bajra,

greengram, blackgram, cowpea,

pigeonpea, groundnut, linseed,

other crops)other crops)

b) Stalks of maize, cotton, jute,

tapioca leaves etc)

c) Other wastes – rice husk, saw

dust, tea waste

Crop residue availability-

Globally

Globally, the total crop residue

production is estimated at 3.8 billion

tons per year(Lal, 2005).

• 74% from cereals• 74% from cereals

• 8% from legumes

• 3% from oil crops

• 10% from sugar crops

• 5% from tubers

Crop residue potential in

India

The Ministry of New and Renewable Energy (MNRE, 2009), Govt. of India has estimated that about 500 Mt of crop residues are generated every year.

1. Cereals - 352 Mt

year.

1. Cereals - 352 Mt

2. Fibres - 66 Mt

3. Oilseeds - 29 Mt

4. Pulses - 13 Mt

5. Sugarcane - 12 Mt

Cereals - cereal crops (rice, wheat, maize, millets) contribute 70%. Rice crop alone contributes 34% to the crop residues. Wheat ranks second with 22% of the crop residues

Fibres - Fibre crops contribute 13% to the crop residues generated from all crops. Among fibres, cotton generates maximum (53 Mt) with 11% of crop maximum (53 Mt) with 11% of crop residues. Coconut ranks second among fibre crops with generation of 12 Mt of residues.

Sugarcane - Sugarcane residues comprising of tops and leaves, generate 12 Mt, i.e., 2% of the crop residues in India.

State Crop

residues

generation,

(MNRE,

2009)

Crop

Residues

surplus(MNR

E, 2009)

Crop

residues

burnt (based

on IPCC

coefficients)

Crop surplus

residues

burnt

(Pathak

et al. 2010)

HP 2.85 1.03 0.20 0.41

J & K 1.59 0.28 0.35 0.89

Jharkhand 3.61 0.89 1.11 1.10Jharkhand 3.61 0.89 1.11 1.10

Karnatak 33.94 8.98 3.05 5.66

Kerala 9.74 5.07 0.40 0.22

MP 33.18 10.22 3.74 1.91

Maharashtra 46.45 14.67 7.82 7.41

Manipur 0.*0 0.11 0.14 0.07

Meghalaya 0.51 .09. 0.10 0.05

Nagaland 0.49 0.09 0.11 0.08

Odisha 20.07 3.68 2.61 1.34

Punjab 50.75 24.83 9.84 19.62

Rajasthan 29.32 8.52 3.84 1.78

Sikkim 0.15 0.02 0.01 0.01

Tamilnadu 19.93 7.05 3.62 4.08Tamilnadu 19.93 7.05 3.62 4.08

Tripura 0.04 0.02 0.22 0.11

Uttarakhand 2.86 0.63 0.58 0.78

UIttar

Pradesh

59.97 13.53 13.34 21.92

West Bengal 35.93 4.29 10.82 4.96

India 501.76 140.84 91.25 92.81

Fate of crop residues

Left on the soil surface - Eaten by

roaming cattle or allowed for grazing

of cattle by farmer itself

Eaten by roaming cattle or allowed

for grazing of cattle by farmer itself

Multi-purpose uses in household

• Removed from the field and

transported to houses to serve for

multi-purpose uses in the

household as thatching material

and fuel. and fuel.

Crop residues as compost

For preparing compost, crop residues are used as animal bedding and then heaped in dung pits. In the animal shed each kilogram of straw absorbs about 2-3 kg of urine, which enriches it with N. The residues of rice crop from one hectare land, on composting give about 3 tons of manure as rice crop from one hectare land, on composting give about 3 tons of manure as rich in nutrients as farmyard manure (FYM). The rice straw compost can be fortified with P using indigenous source of low grade rock phosphate to make it value added compost with 1.5 % N, 2.3 % P2O5 and 2.5 % K2O (Sidhu and Beri 2005)

Mushroom cultivationUse of residues in mushroom production

represents a valuable conversion of inedible crop residues into valuable food, which despite their high moisture content has two to three times as much protein as common vegetables and an amino acid composition similar to that of milk or meat. of milk or meat.

Wheat and rice straws are excellent substrates for the cultivation of Agaricus bisporus (white button mushroom) and Volvariella volvacea(straw mushroom), two of the four most commonly grown fungi.

Crop residues as bio-fuelBiofuel is an important strategy to reduce

dependence on fossil fuel.

Conversion of ligno-cellulosic biomass into alcohol is of immense importance, as ethanol can either be blended with gasoline as a fuel extender and octane enhancing agent or used as a neat fuel enhancing agent or used as a neat fuel in internal combustion engines.

Theoretical estimates of ethanol production from different feedstock (corn grain, rice straw, wheat straw, bagasse and saw dust) vary from 382 to 471 l t-1 of dry matter.

Crop residues as biocharBiochar is a fine-grained charcoal

having high carbon material produced through slow pyrolysis(heating in the absence of oxygen) of biomass. It can potentially play a major role in the long-term storage of carbon in soil.

Biochar converted from plant Biochar converted from plant biomass contains a unique recalcitrant form of carbon that is resistant to microbial degradation, therefore can be used as a carbon sequester, when applied to soil

Crop residues as livestock feed

• Cultivation of forage crops in

tropical developing countries has

been limited due to inadequate

technical support, such as non technical support, such as non

availability of quqlity forage

seeds/planting materials. Small

farmers in rural areas depend on

crop residues to feed livestock.

Crop residue as surface mulch• Residue retention on the surface of soil seems to be a

better option for conservation of soil and avoiding water losses by evaporation.

• It also reduces the weed seed germination and helps in building of soil microbial populations results in increasing soil organic carbon- a direct indicator of soil health.

• Zero-till wheat has been adopted in the rice wheat • Zero-till wheat has been adopted in the rice wheat system in the northwest IGP with positive impacts on wheat yield, profitability and resource use efficiency.. New advance generation seed drill is evolved for this purpose.

• The Happy seeder works well for direct drilling in standing as well as loose residues provided the residues are spread uniformly.

Crop residues are removed from the

field to serve multiple purposes in the

household

Burnt prior to tillage or land

preparation

• A large portion of the residues is burnt on-farm primarily to clear the field for sowing of the succeeding crop.

The problem of on-farm burning of • The problem of on-farm burning of crop residues is intensifying in recent years due to shortage of human labour, high cost of removing the crop residues by conventional methods and use of combines for harvesting of crops.

• The residues of rice, wheat,

cotton, maize, millet, sugarcane,

jute, rapeseed-mustard and

groundnut are typically burnt on-

farm across different states of the

country. country.

• The problem is more severe in the

irrigated agriculture, particularly in

the mechanized rice-wheat system

of the northwest India.

Crop residue BurntThe farmer is not only cleaning his field, but also

'cleaning his pockets' by burning the potential

fertility of his soil.

Effect of crop residues on

soil properties

Incorporation of crop residues into

soil or retention on the surface soil or retention on the surface

has several positive influences on

physical, chemical and biological

properties of soil.

Year Burnt Incorporate

d

CD(P=0.05) Increase

in yield

1993-94 4.27 4.36 0.27 0.09

1994-95 4.38 4.50 0.28 0.12

1995-96 4.09 4.29 NS 0.20

19896-97 4.85 4.78 NS -

Wheat yield as influenced by rice residue management(Sidhu and Beri)

** Wheat sown late, * Rice straw incorporated 203 weeks before wheat sowing

19896-97 4.85 4.78 NS -

1997-98 4.85 5.21 NS 0.36

1998-99 4.25 4.37 NS 0.12

1999-2000 4.55 5.71 NS 0.16

2000-2001 4.73 4.87 0.12 0.14

2001-02 4.01 5.97 NS -

2002-03 4.70 4.20 0.12 0.50

2003-04** 4.10 3.90 0.30 -

Physical Chemical Biological

Soil erosion Soil organic

matter content

and quality

Carbon and

nutrients in

microbial biomass

Soil aggregation Nutrient status

and availability

Microbial activity

Soil parameters

and availability

Soil bulk density Soil pH Microbial diversity

Soil hydraulic

properties

Cation Exchange

Capacity

Meso and macro

fauna population

and activitiesSoil WHC

Soil moisture and

temperature

Soil erosion• Leaving substantial amounts of

crop residues evenly distributed over the soil surface reduces wind and water erosions, and reduces surface sediment and water runoff.runoff.

• Crop residues act as physical buffer and protect soil from the direct impacts of rain and wind leading to reduced runoff and erosion.

• Retention of crop residues on the

soil surface slows the runoff by

acting as tiny dams, reduces

surface crust formation and

enhances infiltration.

• The channels (macro pores)

created by earthworms and old

• The channels (macro pores)

created by earthworms and old

plant roots, when left intact with

no-till, improve infiltration to help

reduce or eliminate runoff.

Soil aggregation

• Addition of organic matter to the

soil favours formation of

aggregates. Structural stability

increases due to addition of increases due to addition of

straw. Better aggregate size

distribution occurs due to a

reduction in soil disturbance.

Tillage and weed management for maize

(Zea mays L.) in rice-maize cropping

system(Modak and Behera, 2014)

Main plot treatments (Tillage

methods)methods)

CT : Conventional tillage

MT : Minimum tillage

ZT : Zero tillage + Glyphosate

(Glyphosate @ 1 kg/ha)

Treatme

ntpH

EC

(dS/m)

OC

(%)

BD

(g/cc)

Macro-

aggregate

s % (>250

µm)

Micro-

aggregate

s %

(53 -250

µm)

Tillage Methods (CT,MT,ZT)

Soil physical properties is influenced

by tillage method

CT 6.21 0.52 0.692 1.48360.27

18.23

MT 6.16 0.51 0.696 1.47566.49

17.76

ZT 6.13 0.46 0.788 1.44370.88

11.90

SE(m) ± 0.03 0.01 0.004 0.013 0.96 0.53

CD(P=0.0

5)NS 0.02 0.017 NS 3.78 2.07

CV 2.02 4.48 2.565 3.663 6.20 14.03

Soil bulk density

• Incorporation of straw with FYM

reduces the bulk density of soil

and increases the porosity of the

soils.soils.

Soil hydraulic properties

Crop residues increase hydraulic

conductivity by improving soil

structure, microspores and

aggregate stability. aggregate stability.

Soil water holding capacity

• Residue incorporation raises

organic matter content of the soil.

Leading to improvement in water

holding capacity of the soil.holding capacity of the soil.

Soil temperature

• Mulching with plant residues

raised the minimum soil

temperature in winter due to

reduction in upward heat flux reduction in upward heat flux

from soil and decrease soil

temperature during summer due

to shading effect.

Soil moisture

• Presence of crop reduces

evaporation rate due to increase

in amount of residues on the soil

surface and helps in retaining surface and helps in retaining

moisture in the soil.

Chemical parameters

Crop Nutrient

N P K

Rice 0.61 0.09 1.15

Wheat 0.48 0.07 0.98

Nutrient content in crop residues

Wheat 0.48 0.07 0.98

Maize 0.58 0.09 1.25

Jowar 0.52 0.12 1.21

Bajra 0.45 0.07 0.95

Barley 0.52 0.08 1.25

Sugarcane 0.45. 0.08 1.20

Potato 0.52 0.09 0.85

Soil organic matter content

and quality

Continuous addition of crop residue

increases organic matter status

of soil. crop residues

favourcarbon sequestration in favourcarbon sequestration in

soils.

Nutrient status and availability

• Soil OM acts as reservoir for

essential plant nutrients, prevents

leaching of elements, required for

growth and increases CEC.growth and increases CEC.

Soil property Crop residue management

Burned Removed Incorporated

Total P (mg

kg -1)

390 420 612

Total K(mg

kg -1)

17.1 15.4 18.1

Effect CRM on soil fertility in 11 years

of rice – wheat system(Beri et al, 1995)

kg -1)

Olsen’s P(mg

kg -1)

14.4 17.2 20.5

Available

K(mg kg -1)

58 45 52

Available

S(mg kg -1)

34 55 61

Soil pH

The crop residues play an

important role in amelioration of

soil acidity through the release of

hydroxyls especially during the hydroxyls especially during the

decomposition of residues with

higher C:N, and soil alkalinity

through application of residues

from lower C:N crops, including

legumes, oilseeds and pulses.CEC

CEC

• Soil OM as reservoir for essential

plant nutrients, prevents leaching

of elements, required for growth.

Addition of residues increases Addition of residues increases

CEC.

Biological properties

Carbon and nutrients in

microbial biomass

Increased microbial biomass can

enhance nutrient availability in

soil as well as act as sink and

source of plant nutrients.source of plant nutrients.

Microbial activity

• Crop residues provide energy for

growth & activities of microbes &

substrates for microbial biomass.

• Crop residues enhance activities • Crop residues enhance activities

of enzymes such as urease,

dehydrogenase and alkaline

phosphatase.

Treatment

Microbial population

Bacteria

CFU/ml

(X×105)

Actinomy

cetes

CFU/ml

(X×104)

Fung

us

CFU/

ml

(X×103)

MBC

(µg

C/g

soil)

Soil Microbial Biomass Carbon (MBC)

and microbial population

3)

Tillage Methods (CT,MT,ZT)

CT Conventional tillage 72.0 217.5 42.7 278.3

MT Minimum Tillage 78.0 228.6 47.8 289.3

ZTZero tillage +

Glyphosate

96.0 248.6 55.9314.0

SE(m) ± 2.5 3.3 2.9 5.6

CD(P=0.05) 9.8 12.9 11.5 21.9

CV 12.9 6.0 25.4 8.1

Treatment

CO2 evolution (mg

CO2/100 g soil/day)

Dehydrogenated

activity

(μg TPF/g soil/day)

30

DAS

60

DAS

Maturi

ty

30

DAS

60

DAS

Maturi

ty

CO2 evolution and dehydrogenated activity is influenced by

tillage methods

DAS DAS ty DAS DAS ty

Tillage Methods (CT,MT,ZT)

CTConventional

tillage

12.5

015.44 11.95

11.7

18.96 7.60

MTMinimum

Tillage

14.2

318.15 14.25

13.1

210.62 8.44

ZTZero tillage +

Glyphosate

20.8

323.58 19.13

15.2

713.14 10.47

SE(m) ± 0.35 0.40 0.25 0.25 0.19 0.17

CD(P=0.05) 1.39 1.58 0.96 0.98 0.73 0.68

Microbial diversity

Soil Control(Soi

l)

FYM Wheat/rice

straw

Bajra/Maize

stalk

0.5%

C

2.0%C 0.5% C 2.0%

C

0.5% C 2.0%

C

Bacterial population((10 8/g soil)

Alluvia 32.08 74.83 141.18 92.12 197.7

Microbial population in differentially treated

during organic matter decomposition

(Gaur et al., 1984), NRRI, Cuttack

Alluvia

l

32.08 74.83 141.18 92.12 197.7

6

Actnomycetes population((10 6/g soil)

3.22 9.74 16.08 8.77 13.24

Fungal population((10 4/g soil)

27.15 39.00 48.23 75.54 134.1

5

Meso and macro fauna

population and activities

Crop residue decomposition and

management

• There is great variability in C : N

ratio of the CRs which determine

the rate of decomposition and

release of nutrients.

Materials with high or wide C: N • Materials with high or wide C: N

ratio like rice straw, wheat straw,

rice husk and sugarcane bagasse

decompose slowly.

• Materials with narrow C: N ratio like residues of leguminous crops decompose faster.

• Addition of N in form of fertilizer or cakes to N poor materials accelerates decomposition and can be compared well with N rich materials. materials.

• The decomposition of FYM is slow and steady.

• The order of decomposition ie cakes > legumes > cereal + cakes > cereal> FYM.

CRM in rice-wheat cropping

systemIn areas where mechanical

harvesting is practiced, a large

quantity of crop residues are left in

the field, which can be recycled

for nutrient supply. for nutrient supply.

About 25% of N and P, 50% of S,

and 75% of K( uptake by cereal

crops are retained in crop

residues, making them valuable

nutrient sources.

• Both rice and wheat are exhaustive

feeders, and the double cropping

system is heavily depleting the soil

of its nutrient content.

• A rice-wheat sequence that yields 7

t/ha of rice and 4 t/ha of wheat

removes more than 300 kg N, 30 kg removes more than 300 kg N, 30 kg

P, and 300 kg K/ha from the soil.

• Traditionally, wheat and rice straw

were removed from the fields for

use as cattle feed and for other

purposes in South Asia.

• Recently, with the advent of mechanized harvesting, farmers have been burning in situ large quantities of crop residues left in the field.

• As crop residues interfere with tillage and seeding operations for the next crop, farmers often prefer to burn the residue in situ, causing loss of nutrients and organic matter in the of nutrients and organic matter in the soil.

• Unlike removal or burning, incorporation of straw builds up soil organic matter, soil N, and increases the total and available P and K contents of the soil.

• The major disadvantage of incorporation of cereal straw is the immobilization of inorganic N and its adverse effect due to N deficiency.

• Incorporation of cereal crop residues immediately before sowing /transplanting into wheat or rice significantly lowers crop yields. significantly lowers crop yields.

• Due to straw incorporation, wheat yield (mean of 10 years) decreases from 0.54 t/ha to 0.08 t/ha with the application of 60 kg N/ha and 180 kg N/ha, respectively.

• Residue characteristics and soil and management factors affect residue decomposition in the soil.

• Under optimum temperature and moisture conditions, N immobilization can last from four to six weeks.

• Adverse effects of wheat straw incorporation can be averted by

• Adverse effects of wheat straw incorporation can be averted by incorporating both green manure (having narrow C:N ratio) and cereal straw (having wide C:N ratio) into the soil before rice transplanting.

Legume crop residues and

green manures• In northwestern India, short-duration

legumes (e.g., mungbean and cowpea) can be grown in the fallow period after wheat harvest.

• In the rice-wheat system, incorporation of mungbean residue incorporation of mungbean residue after picking pods, significantly increases rice yield and saves 60 kg N/ha.

• The advantages of incorporation of legume crop residues and green manuring to rice are similar.

• Green manures are a valuable potential source of N and organic matter.

• Green manure crops (e.g., Sesbaniasp.) can be used in rice-based cropping systems.

• A 45- to 60-day-old green manure crop can generally accumulate

• A 45- to 60-day-old green manure crop can generally accumulate about 100 kg N/ha, which corresponds to the amount of mineral fertilizer N applied to crops.

• Sometimes green manure crops accumulate more than 200 kg N/ha.

• Integrated use of green manure and chemical fertilizer can save 50-75% of N fertilizers in rice.

• Green manuring also increases the availability of several other plant nutrients through its favourable effect on chemical, physical, and biological properties of soil. properties of soil.

• In Bangladesh, N supplied by Sesbania green manure was effective for rice grown in coarse-textured soils but its residual effect on the following crop of wheat was negligible.

Rice straw management

practices

• Incorporation of rice straw before wheat planting compared to wheat straw before rice planting is difficult due to low temperatures and the short interval between rice harvest and wheat planting.short interval between rice harvest and wheat planting.

• Farmers use different straw management practices: burning, removal, or incorporation.

• Rice and wheat yields under these practices are generally similar.

• In few studies, wheat yields were lower during the first one to three years of rice straw incorporation 30 days prior to wheat planting, but in later years, straw incorporation did not affect wheat yields adversely.

• In contrast, rice straw incorporation gave significantly higher wheat yields of 3.51 t/ha compared to 2.91 t/ha with gave significantly higher wheat yields of 3.51 t/ha compared to 2.91 t/ha with straw removal in Pakistan.

• Incorporation of rice straw three weeks before wheat sowing significantly increased wheat yields on clay loam but not on sandy loam soil.

• About 10-20% of N supplied through organic materials having high C:N ratio such as rice straw and stubble is assimilated by the rice crop, 10-20% is lost through various pathways, and 60-80% is immobilized in the soil. immobilized in the soil.

• Addition of 10 t/ha rice straw at 4 -5 weeks before transplanting rice is equivalent to the basal application of 40 kg N/ha through urea.

• Proper fertilizer management practices can reduce N-immobilization due to incorporation of crop residues into the soil.

• These practices include appropriate method, time, and rate of fertilizer-N application.

• The following options can reduce the • The following options can reduce the adverse effects of N immobilization:

1. Place N-fertilizer below the surface soil layer which is enriched with carbon after incorporation of crop residue.

2. Apply N-fertilizer at a higher dose than the recommended dose.

Effect of starter dose of N on

CRM

When cereal straw is added in soil, growth of crop declines. This is attributed to several factors. Added straw fixes N during early stages of decomposition of soluble carbohydrates resulting in N deficiency to the subsequent crop. soluble carbohydrates resulting in N deficiency to the subsequent crop. Inorganic N should be added to promote decomposition of straw in time. Added N enhances the rate of decomposition measured in terms of CO2 production and loss of total C from soil.

• Application of 15 to 20 kg N/ha as starter dose with straw incorporation increases yields of wheat and rice compared to either burning of straw or its incorporation in the soil.

• At recommended fertilizer-N level, rice straw incorporation reduces rice yields than urea alone.

• Therefore, a higher dose of urea-N application with rice straw incorporation is application with rice straw incorporation is necessary to get good yields.

• The beneficial effect of straw incorporation before rice planting does not carry over to the succeeding wheat crop.

• Application of 30 kg extra N/ha than the recommended fertilizer dose, increases rice yields only slightly.

Beneficial effects of wheat

crop residues• During a 10-year (1984 to 1994) long-term

field experiment conducted in India, comparisons were made between the application of wheat crop residues versus inorganic fertilizers on rice and wheat.

• In the first year, inorganic fertilizer-treated plots of rice and wheat yielded treated plots of rice and wheat yielded the highest.

• However, in the second and third year, yield from the treatment with combined application of wheat straw and inorganic fertilizer was similar to that with inorganic fertilizer alone

• Beyond fourth year, plots treated with a combination of wheat straw and inorganic fertilizer outyieldedall other treatments.

• Another long-term study (1988 to 2000) conducted in Punjab, India showed that wheat straw could be showed that wheat straw could be combined with green manure with no adverse effect on rice yield.

• Yield and N-use efficiency in rice, however, were reduced with wheat straw incorporation.

• Results from the All India

Coordinated Agronomic Research

Project showed the beneficial effects

of wheat crop residues when

applied as a substitute for chemical

fertilizer needs of rice in the rice-

wheat cropping system. wheat cropping system.

• In another study, incorporation of

wheat straw (10 t/ha) saved 50% of

the recommended fertilizer dose (60

kg N + 13.1 kg P + 25 kg K/ha) and

helped achieve higher yield of rice.

Adverse effectsImpact of crop residues on pestsIncorporation of crop residues inconservation agriculture has direct andindirect effects on pests.

Crop residues directly affect egg layingof beetles and cutworms. Lower soiltemperature and higher soil moisturetemperature and higher soil moisturecontent under crop residues would alsoaffect pest infestation.

Indirectly, residues change the typeand density of weeds, which in turninfluence insects and natural enemies.Crop residues generally increasediversity of useful arthropods and helpin reducing pest pressure.

• The surface residues may ensure survival of a number of insects, both harmful and beneficial. Reduced tillage systems particularly under staggered planting system of crops in monoculture, may contain higher levels of pest inoculums than the conventional system.

• Further, the decomposition of crop residues along with several inter-related residues along with several inter-related factors like climate, crop geometry, irrigation and fertilization, cultural practices and pesticides may affect the survival of insects in crop residues.

• The decomposition of residues brings out a chemical change in soil which may affect the host reaction to pests.

• The decomposition of plant residues may produce phytotoxic substances, particularly during early stages of decomposition. The effects could be severe in reduced tillage systems which incorporate huge amount of crop residues into the soil and an extra application of N is made to hasten decomposition of these residues. A change in weed ecology is expected to influence the survival of is expected to influence the survival of several of those insects which tend to develop on weeds, particularly during the fallow period. Since the zero/reduced tillage system reduces the fallow period among crops, it may result in altered incidence of certain insects.