In the United States we have tremendous potential as a result of high yields and large-scale producers. The western part of the US corn belt produces more than 40% of the world’s corn and soybean. Despite problems and concerns, we expect that high yields will be maintained—even in the face of major shocks—and that our agricultural practices will have acceptable environmental effects. We know that climate change will have an impact, but, because we are resilient, there is the expectation that we will keep producing and feed ourselves. But without serious efforts to curb water use, this expectation may be wrong. And the situation in some countries in the developing world is dire. Collaboration and research are needed to overcome this.

Chapters: 1) Public goods and farming. 2) Pesticides and sustainable agriculture. 3) Nitrogen use efficiency by annual and perennial crops. 4) Microalgae for bioremediation of distillery effluent. 5) No-till direct seeding for energy-saving rice production in China. 6) Agricultural water poverty index for a sustainable world. 7) Participatory rural appraisal to solve irrigation issues. 8) Bioavailability of soil P for plant nutrition. 9) Animal manure for smallholder agriculture in South Africa. 10) Vermicompost and soil quality.

To meet the food demand of a growing global population, agricultural production will have to more than double in this century. Agricultural land expansion combined with yield increases will therefore be required. This thesis investigates whether enough water resources will be available to sustain the future food production. Using a global scale hydrology and crop growth model, the combined effect of climate change and socio economic changes on water scarcity and food production were quantified. The first thing to explore was where water for agriculture is currently extracted. Reservoirs behind large dams are found to be very important for agriculture and contribute around 18% of the total irrigation water today. It is shown however that with current reservoir capacities and irrigation efficiencies, not enough water can be supplied to sustain an increased food production. Irrigation water shortage can lead to a loss of 20% of the irrigated crop production globally, but with important regional differences. Regions particularly at risk include basins in Southern Africa and South Asia, where production losses on irrigated cropland can become over 50%. This means that unless major investments are made towards improving irrigation efficiency and increasing storage capacity, water shortage will put a serious constraint on future food production.

To meet the food demand of a growing global population, agricultural production will have to more than double in this century. Agricultural land expansion combined with yield increases will therefore be required. This thesis investigates whether enough water resources will be available to sustain the future food production. Using a global scale hydrology and crop growth model, the combined effect of climate change and socio economic changes on water scarcity and food production were quantified. The first thing to explore was where water for agriculture is currently extracted. Reservoirs behind large dams are found to be very important for agriculture and contribute around 18% of the total irrigation water today. It is shown however that with current reservoir capacities and irrigation efficiencies, not enough water can be supplied to sustain an increased food production. Irrigation water shortage can lead to a loss of 20% of the irrigated crop production globally, but with important regional differences. Regions particularly at risk include basins in Southern Africa and South Asia, where production losses on irrigated cropland can become over 50%. This means that unless major investments are made towards improving irrigation efficiency and increasing storage capacity, water shortage will put a serious constraint on future food production.