4.10 Water conserving plants for agriculture in arid and semi-arid areas (Siegmar Breckle & Manfred Küppers)
Water conserving plants for agriculture in arid and semi-arid areas: Nutrition of mankind relies on very few major domestic plant species conventionally grown in moderate climates. In hot and dry areas or at low water availability such species or varieties become essential that exhibit higher drought and heat resistance. Since their productivity always depends on a combination of highly variable abiotic (environmental, technical) as well as biotic factors, it is the search for the best combination of all of these factors that leads to optimum yield: High water-use efficiency (WUE) and carbon partitioning are species-specific key characters. For the latter it must be taken into account that commercially useful yield may constitute only a small fraction of overall plant-specific biological productivity despite a high
WUE. Use of irrigation water in arid areas is unavoidable, therefore irrigation techniques keeping salinity low (by applying leaching and drainage systems) and minimising evapotranspiration are the other pre-requisite for sustaining productivity. An adequate combination of special land use techniques (minimising waste of water) with the cultivation of drought and heat resistant genotypes can potentially result in more productive and yet sustainable agriculture even in hot and dry regions.