Thomas Lumpkin
International Maize and Wheat Improvement Center 相关阅读

Farmers in dryland (rainfed) areas are experiencing increasing strain on production due to a combination of pressures from soil degradation, weather volatility, water scarcity and labor availability. However, rainfed agriculture has some of the greatest yield gaps and therefore greatest potential for increased production by closing the gap between farmers’ yields and yields achieved in controlled research plots. Closing this yield gap can ultimately contribute to meeting the global food demands of 15 billion people by the end of the century. 
Many of the world’s rainfed agriculture areas correspond with areas of absolute poverty and child malnutrition, suggesting a strong correlation between water scarcity and poverty. Currently, an estimated 1.11 billion people or 17% of the global population live on agricultural production systems which rely on water-constrained environments. In these areas, every 1% increase in agricultural yield translates into a 0.6-1.2% decrease in the number of absolute poor.
Cereal demand is expected to increase by 60-70% by 2050. Researchers now estimate that 85% of this projected increased demand can be met by improving productivity of existing lands. Recent studies estimate that a 7% expansion of rainfed agricultural land will be needed to meet rising food demands.
However other estimates predict that if only 20% of the yield gap in rainfed areas is bridged, these areas will need to be expanded by 400 million ha in order to meet food demands by 2050, an increase of 53%. Yields per hectare must be dramatically improved in order to avoid these levels of expansion. With the combined pressures of climate change, urban sprawl of cities, natural resource degradation and competition with forest areas for agricultural land, this level of expansion will not be possible.
Precise use of fertilizers, high yielding varieties, and adoption of water-harvesting and resource conserving techniques can all contribute to our ability to address and reduce yield gaps in rainfed areas. Water-harvesting and moisture-fertilizer optimization technologies are especially needed in order to secure the livelihoods of farmers in semi-arid areas. 
Since the 1960’s, production increases in rainfed agriculture has mainly originated from land expansion. As the worlds’ population now occupies nearly a third of the earth terrestrial surface for agricultural production, little productive virgin land remains for further expansion. In order to address yield gaps in current dryland agricultural areas, appropriate measures must be put in place which are tailored and site specific, utilizing the latest advances in conservation agriculture, intercropping, precision agriculture and ICT technologies in a matter which takes into account socioeconomic conditions and geographic variations.
International cooperation has the capacity to synergistically utilize lessons learned and new developments from other areas of the world and combine these with site specific knowledge and socioeconomic data. CIMMYT’s projects MasAgro – Sustainable Modernization of Traditional Agriculture in Mexico and SIMLESA - Sustainable Intensification of Maize-Legume cropping systems for food security in Eastern and Southern Africa, have demonstrated yield increases of 62% for rainfed maize yields through conservation agriculture techniques in Mexico and 66% for intercropping systems in sub-Saharan Africa. These projects have tremendous potential to serve as models for improvement of productivity in many other analogous regions.
In order to achieve similar yield increases in other areas, the international community must broaden its collaborative efforts and expand investment in dryland agricultural production. Improved, sustainable, and site specific agronomic approaches adapted to local knowledge must be disseminated with modern ICT extension services to effectively diminish yield gaps in rainfed areas.
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