Agriculture Reference
In-Depth Information
Table 3.4
Yield and total
CH
4
emissions from six rice
varieties. (Source: Mitra
et al.
1999
)
Variety
Total methane emission (Kg/ha) Yield (t/ha)
Pusa 169
15.63
6.5
Pusa Basmati
26.31
4
Pusa 834
24.02
6.4
Pusa 1019
26.97
4.8-7.1
Pusa 677
16.91
3.2-7.3
Pusa 933
27.24
5.5-7.5
Fig. 3.2
Methane emission
from rice culms at differ-
ent depths of flood-water
(mean ± SE,
n
= 3). (Source:
Wang et al.
1997b
)
1.0
0.8
0.6
0.4
0.2
0.0
5.5
12.5
26.5
38.0
water depth (cm)
The capacity of methane emission varies widely among rice cultivars (Shalini
et al.
1997
; Sigren et al.
1997
; Kesheng and Zhen
1997
) but only variation in CH
4
transport capability is insufficient to explain the variability of CH
4
emission poten-
tial among different cultivars (Aulakh et al.
2000b
).
8.6 Manipulation of Plant Root Properties
Root exudation ability of different cultivars (Wang et al.
1997b
; Wassmann and
Aulakh
2000
), stages of crop growth, gas transport capability, type and amount
of aerenchyma (Aulakh et al.
2000a
; Butterbach-Bahl et al.
1997
) also impart ad-
ditional variability in CH
4
emissions. Rice plants provide methanogenic substrate
through root exudates, help in transport of CH
4
and O
2
through aerenchyma and
establishment of an active CH
4
oxidizing-site in the rhizosphere (Wassmann and
Aulakh,
2000
). Mitra et al. (
2005
) reported that decomposition of root exudates is
one of the causes of CH
4
emission from rice soil. However, the rates of CH
4
produc-
tion vary with soil types and CH
4
production is positively correlated with degree of
aeration in the field. Redox potential of soil is one of the major factors that influence
methane production and gas exchange capacity in the rice field (Kludze et al.
1993
;
Fig.
3.2
).
