Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 287

Table 13.2 Estimated crop residues in India 2006-2007
(Dixit et al. 2010 )
Crop residues

providing crops with equally adequate
amounts of nutrients.
• The addition of organic residue to the soil
reduces environmental pollution potential
while maximizing the N use effi ciency and
providing crops with suffi cient N.
Co-benefi ts of organic amendments applied to
soil are a reduced need for herbicides by reducing
weed emergence and enhancing soil quality,
which provides better habitat for benefi cial soil
fauna. For example, decomposers such as earth-
worms can help in organic amendments. The
castings and the channels that earthworms create
improve root growth, water infi ltration, and the
physical structure of the soil. Earthworms also
stabilize soil organic matter and contribute to the
formation of stable soil aggregates.
(ii) Disadvantage
• The carbon and nitrogen mineralization
rate of these manures and organic residues
are relatively low for the recovery of N,
which ranges between 5 and 18 % of total
N for manures and 8 % for compost. Thus,
these organic amendments would need to
be applied in huge amounts in order to
considerably increase the short-term N
supply, which would lead to higher costs.

Dry weight (million tons)

Cotton stalks 16.36

Maize cobs 2.72

Pigeon pea 6.93

Sunfl ower 2.46

Castor 1.41

biological pest and weed management, crop
rotation, and mechanical cultivation to sustain
and enhance soil productivity and fertility with-
out the use of synthetic N fertilizer and pesti-
cides (Table 13.2 ). The handling of crop
residues also has an impact on net carbon gains.
Removal of straw or stover can result in signifi -
cant loss of soil organic carbon (SOC). If they
are used as bedding for livestock, then much of
the carbon may be returned to the soil as manure
(Lal et al. 1998a ).
Crop residue management through vermi-
composting brings about 463 mg CO 2 e m −2 h −1
compared to their anaerobic digestion value of
694 mg CO 2 e m −2 h −1 . The experiments done by
Chan et al. ( 2011 ) in Australian cities clearly
confi rm the reduction in GHG emissions through
crop residue and vermicompost management.
There will be ample opportunity for farmers to
reduce GHG emissions in vermicompost pro-
duction by reducing the use of chemical fertil-
izers which generally initiate the emission of
N 2 O and CH 4 .
(i) Advantages
• When crop residue is incorporated into
soil, the soil's physical properties and its
water-holding capacity are enhanced.

13.1.4 Water Management

About 18 % of the world's croplands now
receive supplementary water through irrigation
(Millennium Ecosystem Assessment 2005 ).
Expanding the use of irrigation or using more
effective irrigation measures can enhance carbon
storage in soils through enhancing yields and
residue returns. However, some of these gains
may be offset by CO 2 from energy used to deliver
the water or from N 2 O emissions from higher
moisture in the soil and increased fertilizer
inputs. Quantifying these emissions requires
additional research.
Cropland drainage in humid regions can also
promote productivity, and hence soil carbon, and
perhaps also suppress N 2 O emissions by improv-
ing aeration. However, nitrogen loss through the
drainage might be susceptible to loss as N 2 O.

• Organic residues and N fertilizers increase

soil organic carbon and subsequently
improve soil structure and aggregate
stability. By stabilizing soil aggregates,
soil organic matter is more protected from
microbial decay (Six et al. 1999 ). The use
of organic residue management cover
crops and manures can lead to soil organic
carbon accumulation by improving
aggregation as well as reducing the need
for synthetic fertilizer application while