Agriculture Reference
In-Depth Information
higher even if sown early in the season in October. In central and eastern India, mild
winters and water shortages limit crop growth duration. Under such situations, geno-
types having
Vrn
allele and partial vernalization requirements can be seeded early, to
increase growth duration and yield. Early sowing of such genotypes can help farmers
use receding conserved soil moisture for good crop establishment and prelude the need
of presowing irrigation. In an experiment conducted for 2 years, the author planted a
number of genotypes developed for specific adaptations (zero-till/conventional tilled
conditions on two planting dates—early in the last week of September and timely sow-
ing in the mid-November). Under the early-sown condition, days to flowering were
drastically reduced (39.8%-44.7%) in the genotypes HD2329 and CSW2; moderately
reduced (30.4%-33.3%) in CSW1, CSW13, and CSW6; and comparatively less reduced
in PBW343 and HD2967 (24.7%-25.5%). In CSW18, which has a
Vrn-a
allele similar
to many other genotypes, the vernalization requirement seemed to be stronger than all
other genotypes, and therefore the percentage reduction in flowering time (12.8%) was
least. Therefore, genotypes such as CSW18, having a more vegetative phase (days to
flower decreased just by 12.8%), can stabilize wheat yield at a higher level if planted
early in the season under conserved soil moisture conditions (Tables 5.3 and 5.4).
5.6.6 E
arly
W
hEat
S
EEding
With
a
ppropriatE
c
ultiVarS
for
f
urthEr
i
ntEnSification
In the last few years, a series of experiments on early seeding of wheat have been con-
ducted at the Indian Agricultural Research Institute, New Delhi, to reach the conclusion
that early seeding in early/mid-October in the Indo-Gangetic plains is feasible with-
out yield penalty only with specially bred cultivars having weak vernalization require-
ments. Weakly vernalized wheat genotypes are also expected to mature earlier than the
normal-sown (November) wheat crop. The development of such new genotypes also
provides scope for further intensification (seeding a short-duration crop [green gram,
Vigna radiata
L.] in standing wheat or after early crop harvest; Figure 5.5) and the sus-
tainability of the intensively irrigated rice-wheat cropping systems.
Seeding a green gram crop not only helps improve organic carbon sequestration
in cereal systems such as the rice-wheat system but also helps mop up the resid-
ual nitrates from the surface soil layers, which otherwise expectedly would leach
down during the rainy season. The build up of nitrate-N in aquifers has earlier been
reported to be due to deep percolation losses of nitrate-rich rainwater during the
monsoon season. Early seeding of wheat in October can be done in residual moisture
soils of rice crop, and also obviate the need of irrigation in March/April. The saved
water can be used to raise an additional mung crop in tube-well irrigated areas.
In a recent field study, 10 elite, most preferred wheat cultivars by Madhya Pradesh
farmers were planted at weekly intervals along with the newly developed genotype
CSW18 to explore possibilities for October seeding without yield penalties. Results
presented in Figure 5.6 show that weakly vernalized CSW18 and HD2967 genotypes
(see Figure 5.6) developed recently at the Indian Agricultural Research Institute,
New Delhi, had significant yield advantage at early planting. It was observed that
CSW18 outyielded the high-yielding wheat cultivar HD2967 in October planting,
