Increasing efficiency of agricultural water use

Increasing efficiency of crop water use
Developing long-term strategies for agricultural use of scarce water resources

Context

Agriculture is the world's biggest water consumer, accounting for about two-thirds of global freshwater use. Yet studies show that only around 30 to 40% of the water used actually reaches crops. This translates into a gross wastage of water, particularly at a time when competition for water resources is rising sharply as a result of rapid population growth and non-agricultural global development. In addition, excess water use in agricultural irrigation can lead to salinization, alkalization, waterlogging, and desertification of the soil, rendering the land useless for agricultural purposes. In order to reduce water scarcity and problems of water over-application, water efficient methods and technology in agricultural activities are required.

This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities. Agenda 21 recommends increased efficiency and productivity in agricultural water use for better utilization of limited water resources. It also recommends developing long-term strategies and practical implementation programmes for agricultural water use under scarcity conditions with competing demands for water.

Implementation

In 1993, the UN Food and Agriculture Organization (FAO) completed two computer programmes to help increase the efficiency of water use in agriculture. AQUASTAT is a global database on water use in rural development, aiming to improve water management by gathering and disseminating information on irrigation, water drainage, environmental impact of water resources development and water balance in rural areas worldwide. In 1993, AQUASTAT underwent a pilot phase involving tests in five countries around the world, after which the fine-tuned and completed computer programme was set up. SIMIS (Scheme Irrigation Management Information System) is designed to help reduce water losses in irrigation. SIMIS features include: programming for adaptability to diverse local situations by use of independent modules covering a range of irrigation management topics; processing information on one or several projects, making rapid and precise calculations to assess needs possibilities; streamlining routine activities. SIMIS has been used in pilot phases, trial periods and training workshops in various countries.

Intercropping can increase the efficiency of water use by crops when they are growing together. At Machakos, Kenya a pure maize crop utilizes only 30% of the available rainfall, while a maize-leucaena system utilizes 76%.

Novartis Seeds has a programme to develop water-efficient and salt-tolerant crops, including genetically engineered varieties of wheat. Researchers in Mexico have announced the development of drought-resistant corn that can boost yields by a third. Biotechnologists are converting annual crops into perennial ones, eliminating the need for yearly planting.

Claim

There are vast opportunities for increasing water efficiency in arid regions, ranging from installing better water-delivery systems to planting drought-resistant crops. Scientists can help push back the physical frontiers of cropping by developing varieties that are more drought resistant, salt tolerant, and early maturing. The payoff on the first two could be particularly high.

Counter-claim

Producing a ton of grain consumes a thousand tons of water – that is the amount transpired by the wheat as it grows. It is estimated that biotechnology might cut the amount of water a plant uses by ten percent But plant physiologists think this is optimistic because water is such an important part of photosynthesis. They suggest that perhaps the improvement is a mere five percent.