Agriculture Reference
In-Depth Information
the collapse of the Soviet Union. As production declined by nearly 54%
(1989-1994), the solution formulated by the government was to transform
the country's methods of food production from a high-input monoculture
to a low-input, more sustainable system in order to avoid starvation and
famine [61]. Work animals replaced tractors, natural pest controls became
preferred over chemical applications, and state incentives attracted work-
ers, all of which contributed to the production of a suffi cient and success-
ful food supply. Many of these practices are still common management
strategies used today. Both countries are examples of what can happen
when fossil fuels are removed from the modern agricultural system, and
shed suffi cient evidence on the importance of proper resource manage-
ment, and breeding for low-input systems given the inevitable decline in
valuable worldwide resources.
Plants require nitrogen (N) for growth and optimal yield, and although
it is one of the most abundant recyclable elements on Earth, it is often
the most limiting resources in agricultural systems. In high-input systems,
nitrogen is heavily applied as an ammonium salt derived from the Haber-
Bosch process, however in low-input systems nitrogen is provided primar-
ily by managing on-farm resources (compost, manure, legume rotation)
and nitrogen cycling in the soil is driven by soil microbes, often leaving
low-input and organic farming systems with limited nitrogen pools [62].
Unfortunately, most breeding programs select varieties where fertilizers
are liberally applied to ensure maximum production at optimal conditions,
and are not well adapted to low-input systems. By breeding for varieties
that are more adapted to limiting conditions, improved nitrogen use can
help increase yields obtained from low-input systems, reduce fertilizer
production, and potentially not only maintaining the energy required for
crop production, but reducing it, all while feeding a growing population.
Baligar et al. [58] estimated that the overall effi ciency of applied nitro-
gen fertilizers is around 50%, and that improvements in uptake and utiliza-
tion can greatly increase the effi ciency of fertilizers. Several studies have
shown that for several traits, genetic inheritance was different in crops
produced under high- and low-N inputs [63,64], indicating that different
genetic elements are responsible for responding to different inputs. Gallais
and Coque [65] determined that under low-N input, genetic variation in ni-
trogen use effi ciency (NUE) is more important to yield improvement than
