EFFECTS OF SPATIAL COUPLING OF WATER AND FERTILIZER APPLICATIONS ON ROOT GROWTH CHARACTERISTICS AND WATER USE OF WINTER WHEAT

Root systems play vital roles, inter alia in the acquisition of water and nutrients in all plants, and hence in their growth, physiology and metabolism. However, much remains to be learned about the mechanisms affecting root distributions and uptake efficiencies. These are important aspects to understand in order to optimize water and fertilizer applications, especially in arid areas such as the Loess Plateau of China, where a key crop is winter wheat. Therefore, we have studied the effects of spatial coupling of water, nitrogen and phosphorus applications on winter wheat root growth patterns at different growth stages and in different soil layers in soil columns. Observations by minirhizotrons showed root length, surface area, volume and number to be respectively 18.9, 25.3, 29.8 and 8.0% higher under dry treatments than under wet treatments. Simultaneous application of nitrogen and phosphorus in the 090 or 030cm layers promoted extensive spatial distributions of roots, especially in the 030cm layer. In addition, water use efficiency (WUE) was found to be strongly correlated with root length, surface area, volume and number (r 2 = 0.720.80, n = 26), but weakly correlated with root biomass (r 2 = 0.3).