The effects of nitrogen and phosphorus on the water sensitivity and physiologica l parameters of summer maize
氮磷营养对夏玉米水分敏感性及生理参数的影响

As water is a major factor limiting agricultural productivity in dryla nd farming, it is very important, and possible, to regulate crop water use throu gh fertilizer application under limited water resources. There are extensive re searches reported on water sensitivity of different crops during different growt h stages, however, there are few reports on the effect of inorganic nutrients on crop water sensitivity. In terms of methods and crops used in studies, the rep orts about the impact of inorganic nutrition on crop growth and development unde r water deficit conditions are inconsistent. The results presented in this pap er address three issues: (1) the effect of nitrogen (N) and phosphorus (P) on su mmer maize's water sensitivity; (2) the function of inorganic nutrition in adjus ting summer maize's CO-2 and H-2O exchange parameters and growth of roots and shoot s; and (3) better solutions to fertilizer application for better water-saving i rrigation schemes. Potted summer maize was used in the experiments. Six fertilizer treatments and two water treatments were used. Based on the experimental data, the water suppl y model of summer maize in the Loess Plateau was proposed with reference to Jens en's model. The results show that water sensitivity index of summer maize reach es the highest value from the booting to heading stages, and from heading to fil ling stages, and becomes comparatively low before booting and after filling. At a high fertilizer application rate, a higher water sensitivity index is achieve d at key water-demand stages than that at unimportant water-supply stages. Hig her N & P application rates also increase the photosynthesis rate, transpiration rate and water-use efficiency. The root dry matter under a high N level is low er than that under a low N level; the use of P boosts root growth obviously, and the enhancement under 50% Relative Soil Water Content (RSWC) is greater than th at under 80% RSWC. The increase of above-ground biomass under different P trea tmen ts was greater than that under different N treatments distinctly. The root/shoo t ratio is increased with the improvement of water condition. Under different wa ter supply conditions, the use of N reduces the root/shoot ratio while the use o f P raises it.ater