Cropping systems and crop complementarity in dryland agriculture to increase soil water use efficiency: a review

摘要

Dryland agriculture under rainfed conditions is found mainly in Africa, the Middle East, Asia,and Latin America. In the harsh environments of Sub-Saharan Africa (SSA) and West Asia andNorth Africa (WANA), water is the principal factor limiting crop yield. A review has beencarried out on soil and crop management research that can increase the water use efficiency.The WANA production systems are dominated by cereals, primarily wheat in the wetter andbarley in the drier areas, in rotation with mainly food legumes such as chickpea, lentil andforage legumes. The SSA production systems are generally characterized by cereal/legumemixed-cropping dominated by maize, millet, sorghum, and wheat. The major constraints in bothregions to crop production are low soil fertility, insecure rainfall, low-productive genotypes, lowadoption of improved soil and crop management practices, and lack of appropriate institutionalsupport.Different cropping systems and accompanying technologies are discussed as well asselected examples of impact of these technologies. Results indicate that there is an advantage to2apply these technologies but being function of socio-economic and bio-physical conditions. It isrecommended that future research focuses on integrated technology development while takinginto account also different levels of scale such as field, village, and watershed.