Effect of increased fertilizer applications to wheat crop on soil-water depletion in the Loess Plateau, China

Winter wheat monoculture occupies a large area of the Loess Plateau dryland region of China. Its yield is mainly limited by available water and fertilization. From the mid- 1980s, yield of winter wheat increased with fertilizer application, and this increased productivity may increase soil-water depletion and reduce available soil-water at planting. Besides rainfall during the growing season, an important source of water for the crops is stored soil-water at planting. In the long run, increasing fertilization may not be sufficient to maintain higher yield. To develop better dryland crop and water management practices, a 15-year experiment of winter wheat monoculture was conducted at the Changwu Agri-ecological Station of the Loess Plateau from 1984 to 1999. Different levels of productivity were implemented by the application of chemical fertilizers and manure. The experimental design consisted of a control treatment (CTL) and three fertilizer treatments: nitrogen, phosphorus and manure (NPM), nitrogen and phosphorus (NP), and manure (M). Compared to CTL, on average, treatments NPM, NP and M increased yield by 148, 110 and 59%, and decreased soilwater at planting by 102.6, 59.1 and 31.6 mm within the 300 cm profile, and soil-water at harvest by 142.3, 102.5 and 70.2 mm, respectively. There was a decrease of soil-water with time for fertilizer treatments. Crop yield with high fertilization treatments responded more to rainfall variations. Considering the importance of soil-water at planting for crop yield in dryland farming, winter wheat monoculture with high fertilization does not appear to be a sustainable management practice in the Loess Plateau dryland region of China. (C) 2002 Elsevier Science B.V. All rights reserved.