The key driving factors of irrigation water productivity based on soil spatio-temporal characteristics

Abstract

Reasonable uses of water resources can promote the development of oasis agriculture and avoid re-desertification of reclaimed land. Therefore, knowledge of the distribution of irrigation water productivity and its relationship with soil properties is important to cope with water scarcity and ensure food security. A total of 118 sampling points were selected within the study area of 120 km2 (1 km × 1 km grid) in the oasis field of arid Northwest China, where the soil organic matter, total nitrogen, nitrate nitrogen, total phosphorus, available phosphorus, bulk density, soil water content, silt content, sand content and irrigation water productivity (IWP, yield per unit applied irrigation water) were analyzed. The traditional statistics, geostatistics and partial least squares methods (PLS) were used to investigate: i) the spatial distribution of soil properties and their changes with the cultivation years; ii) the relationship between IWP and soil properties; iii) the key driving factors of IWP from the soil factors. The results showed that soil organic matter, total nitrogen, total phosphorus, soil water content and silt content increased with the increase of cultivation years, and the correlations were significant except for total phosphorus, while the sand content showed the opposite trend; and there was no significant relationship between bulk density, available phosphorus and nitrate nitrogen with the cultivation years. IWP of oasis irrigated fields varied from 0.55 to 3.46 kg m−3, with a moderate spatial heterogeneity (CV = 40%). The average IWP was 1.48 kg m−3. Compared with the developed areas of water-saving agriculture, the IWP of oasis farmland still has great potential for improvement. The key driving factors of IWP are available phosphorus and nitrate nitrogen, and the IWP can be improved by increasing the application of phosphorus fertilizers and reducing the amount of nitrogen fertilizer in the oasis fields of arid Northwest China. The results provide scientific basis for improving IWP of oasis fields, and have a great significance to the sustainable development of water-saving agriculture in arid areas.