FOOD SECURITY - Science for Agriculture and Rural Development in Low-income Countries - page 49

Risks, threats and opportunities for resource use efficiency gains
Lack of knowledge, the absence of economic incentives and policies to support
sustainable management practices, climatic variability, as well as a shortage of
labour are among the factors that obstruct the realization of potential increases in
resource use efficiency.
In Asia, the intensification of agricultural production, especially animal production,
has increased nitrogen emissions to the environment. Human health and ecosystem
quality have also been negatively affected by the excessive use (and loss) of agro-
chemicals in vegetable production systems. In many regions, clean and safe water is
a scarce resource and competition for available water resources is intense. This
indicates the need for research into water-saving technologies and improved water
use efficiency in agriculture. In many of the 'food baskets' of Africa, it is foremost
the unpredictable and highly variable rainfall that represents considerable production
and financial risks, preventing many farmers from implementing management practices
that increase resource use efficiency (Roetter and Van Keulen 1997; Bouma et al.
2007) It has been realized during recent years that climate change has increased the
severity and frequency of drought (Dietz et al. 2004) and this - in combination with
the devastating impact of HIV/AIDS - has significantly reduced the capacity of the
rural labour force to maintain adequate and nutritious food supplies. It is very likely
that climate change will further increase weather and yield variability (IPCC 2001;
Parry et al. 2004).
The major measure to improve N recovery of crops is to improve the synchrony
between crop N-demand and N-supply, including N provided by soil reserves,
fertilizer and manure. In practice, this means that the crop-available N pool should
be maintained at the minimum size required to meet crop-N requirements during
each growth stage. More accurate N management results in improved N-recovery,
higher yields and, because less fertilizers are required, increased profits of farmers
(Dobermann et al. 2004). Adoption of such knowledge-intensive management typically
requires additional skills, labour and investments in new equipment, for example, to
monitor crop N status in the course of the growing season.
In the most important crops in South, East and South-east Asia, i.e., rice, maize
and wheat, biomass production per unit water use (= water productivity) is highly
variable, with a factor of 2 between the highest and lowest reported values. Soil
(nutrient) management, water management and crop varieties among others contribute
to these differences. Therefore, crop management offers ample scope to increase
water productivity. Even in rice, which is commonly grown under continuously
flooded conditions, at least 20% of current water inputs can be saved using inter-
mittent flooding conditions without affecting yields. Thus, combining reduced water
inputs and N fertilizer may increase simultaneously yields, water productivity and N
recovery. However, in addition to a very secure and reliable water delivery system,
thorough knowledge on the timing and amount of inputs to be delivered is required
to achieve sustainable water savings.
In Africa, reduction of the protective plant cover by practices such as deforesta-
tion and excessive grazing has increased the rates of soil erosion and runoff. This type
of land degradation can in many cases be reversed by soil and water conservation