Agriculture Reference
In-Depth Information
spacing between “tassel and silks” and weed competitiveness, tolerance to heat and
moisture stresses, etc.). Without a gene pool that is responsive to external use of fer-
tilizer nutrients, a greater input use in agriculture is unlikely to sustain food security
for the teeming millions. Thus, we need to cultivate a wide diversity of plants and
allow them to coevolve with nature. The success of the smallholder farmers always
depend on manipulations of the resources they have on their farms. These small
farmers generally have to adapt their crops to the environment, unlike the large/
big farmers who use resource/inputs to manipulate the environments (e.g., convert
rainfed to irrigated farms, or saline/alkali soils to nonsaline/nonalkali soils). Thus,
we have to appreciate the knowledge of the tribal farmers for using specific land-
races for overcoming a specific bottleneck of production systems. Landraces when
cultivated over many decades consist of plants that have become adapted to specific
conditions of the ecosystems/places where such races are grown. These landraces
had coevolved with agents influencing the resilience of the landraces. Landraces,
evolved in specific environments, respond to specific nutrients, soil moisture, and
thermal regimes/dynamics in a manner that make landraces grow more vigorously
to compete better with weeds and escape disease and pest attacks. Some landraces
do not need much nutrients and water, bind soil particles against erosion, tolerate
temporary flooding, and become more resilient after flooding, and others are able to
cope with drought and heat, soil moisture, and salinity stresses. Yet others have other
traits (e.g., silica hairs), such as to escape insect attack.
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Several earlier reports (Newhouse and Crosbie 1986; Kaspar et al. 1987; Hersterman
et al. 1988; Duiker et al. 2006) had suggested an absence of genotype × tillage
interaction or the presence of non-cross-over-type interactions. Many of the studies
where genotype × tillage interaction is either absent, or are small, have been done
with very limited number of genotypes, and the genotypes used are the products
of breeding programs for conventional tillage. There is a likelihood that genotypes
bred for conventional systems may not show specific adaptability for zero-till con-
ditions. However, an absence of genotype × tillage interaction or the presence of
a non-cross-over-type interaction does not warrant for a separate breeding program
for the zero-till condition. Several recent studies have reported a strong presence of
such interactions under no-till situations (Trethowan et al. 2005; Trethowan et al.
2012; Yadav et al. 2012). A strong presence of genotype × tillage interaction, how-
ever, necessitates the development of cultivars adapted to CA. The adaptation can
be improved by selecting the segregating material as well as by testing of advanced
lines under the zero-till condition. Yadav et al. (2012) investigated the genotype ×
tillage interactions among 720 wheat genotypes selected from advanced breeding
lines (F6 generation) grown on permanent untilled raised beds, as well as under
conventional tilled conditions in maize-wheat, pearl-millet-wheat, and rice-wheat
systems.
These lines were then tested for their specific adaptation for permanent bed or
for conventional tillage conditions. It was observed that the top 20 best-performing
