Encourage farmers to adopt sustainable water and nutrient management in arid agroecosystems: problems, solutions and future studies

Abstract

Crop production is seriously threatened by drought. Greater availability of nitrogen and phosphorus through intercropping with grain legumes and inoculationwith Phosphate Solubilizing Bactaeria (PSB) can alleviate the negative effect of water stress on some crops. However, row crop-grain legume intercropping and using PSB bacteria is not welcomed or widely accepted by smallholder farmers in arid regions. The problem is that N-fixation by grain legumes cannot completely satisfy nitrogen demand of intercropped non-legume row crop especially in low phosphorus soils of these regions under restricted irrigation. The efficiency of PSB bacteria also is very low in the alkaline soil of this region. It suggests that some amount of nitrogen fertilizer should be used in this intercropping system. Nitrogen consumption also improves the efficiency of PSB bacteria. So, consumption of some mineral nitrogen, and incubation with PSB bacteria meet entirely the need for phosphorus fertilizer. Significant water saving by restricting irrigation without significant yield loss in row crop and grain legumes can be regarded as an advantage of this method. So, farmers can cultivate more land with the same amount of water. In such a situation, even small foliage of the grain legumes, as green manure, can convince the farmers to use the row crop -grain legumes intercropping system even under restricted irrigation conditions. Futures studies must focus on a better understanding of competition and facilitation of two crops for water and nutrients. They also must pay attention to nitrogen x PSB bacteria, and Phosphorus x rhizobacteria synergic interactions on yield and resources use efficiency of both crops. These studies may help to better water and plant nutrition management in a way that it is environmentally safe and economical for farmers.