Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 294

Table 13.7 Effect of K fertilization on methane emissions from a rice fi eld (Babu et al. 2006 )

Biomass (g/m 2 )

K level Aboveground Underground

Control (K 0 ) 1,419.21a 189.64a 125.34 25.32
K 30 1,562.90ab 252.23bc 63.81 11.00
K 60 1,557.65ab 236.32b 82.03 14.34
K 120 1,671.00b 287.03c 64.43 10.70
Note : In a column, means followed by a common letter are not signifi cantly different ( P < 0.05) by Duncan's multiple
range test

Cumulative CH 4 (kg/ha) Kg CH 4 /mg grain yield

practice, thereby lowering irrigation water con-
sumption by 25 %, reducing diesel fuel consump-
tion for pumping water by 30 l per hectare, and
producing 500 kg more rice grain yield per
hectare.
The visible success of AWD has dispelled the
concept of yield losses under moisture stress con-
dition in non-fl ooded rice fi elds. The adoption of
AWD technology reduced water use and methane
emissions, and it increased rice productivity. It can
reduce methane emissions by 50 % as compared to
rice produced under continuous fl ooding.
(ii) Disadvantages
• Occasionally, rice productivity is reduced
using AWD technology if moisture stress
condition is induced. However, the reduc-
tion of yield was less compared to the
yield reduction due to the direct moisture
stress effect.

(i) Advantages
• Chemical fertilizers mitigate methane
emissions more quickly compared to the
slow processes of organic amendments.
• Chemical fertilizers also fulfi ll the nutrient
requirements of crops, thus helping in sus-
taining productivity while mitigating
methane emissions.
• Chemical fertilizers sometimes improve
soil health if used with care to maintain
nutrient balance in soil.
In potassium-defi cient soils, applications of
potassium fertilizer generally increase yields
signifi cantly; the value of the increase in yield
exceeds the costs of the fertilizer treatments.
Therefore, under these conditions, the reduction
in methane emissions is an added benefi t whose
mitigation cost is effectively zero. In addition, K
fertilization can reduce methane emissions
by half.
(ii) Disadvantages
• The potassium fertilizer must be precisely
applied in order to avoid negative effects
on fi eld fertility.
• Chemical fertilizers that are applied in
excess to the normal ratio generally
change the nutrient composition of the
soil besides affecting their physical struc-
ture. This affects adversely both methane
oxidation and methanogenesis.

• N 2 O emissions are increased.

13.1.5.4 Potassium Fertilizer
Application
Fertilization with muriate of potash (MOP) can
signifi cantly reduce emissions of methane from
fl ooded soils planted with rice. Potassium appli-
cations to rice fi eld soils prevent a drop in redox
potential and reduce the contents of active reduc-
ing substances and Fe 2 + contents. Potassium
amendments also inhibit methanogenic bacteria
and stimulate methanotrophic bacterial popula-
tions. In addition to producing higher rice bio-
mass (both above- and belowground) and grain
yield, potassium amendments can effectively
reduce CH 4 emission from fl ooded soil, and this
could be developed into an effective mitigation
option especially in potassium-defi cient soils
(Babu et al. 2006 ) (Table 13.7 ).

13.1.5.5 Agricultural Biotechnology
To identify the use of rice cultivars with reduced
methane emissions, Wang et al. ( 2000 ) demon-
strated that rice cultivars with small root systems,
high root oxidative activity, high harvest index,
and productive tillers are likely to produce less