Corn Fertilizer Space Coupling Effect

In arid- and semi-arid area in north China, water shortage is one of the main reasons that crop yield is not high. However. inefficient use of irrigation water is another problem. As agricultue will get less and less irrigating water in the future, in order to produce enogh food for people living there, and to make full and efficient use of irrigating water, spatial coupling of water and fertilizer has been employed as an effective way.In order to find optimal coupling way, we planted corn (Zea Mays L.) in field and pot experiment to research spatial coupling of nitrogen fertilizer and irrigating water in semi-arid area in North China under unsufficient irrigation. By determining the physiological effects on corn plant and movements of soil moisture and nutrition, we found the reasons why different coupling ways have the different effects on corn yield and water use efficiency.In this research, we got following conclusions, (1) In arid area in north China, irrigating corn plant with much less water(1200 m3/ha,1125 m3/ha,600 m3/ha) than that being used at present in this area(2500 m3/ha), less decrease of corn yield will be found (10 to 15 percent), but the water use efficiency being increased significantly. Compared with traditional irrigation(2500 m3/ha), water use efficiency of treatments with 1200 m3/ha, 1125 m3/ha, 600 m3/ha irrigating water increased 31.63 percent, 40.77 percent and 143.22 percent, respectively.All three spatial coupling ways, namely, alternate irrigation- evenly fertilizing(AIEF), alternate irrigation- fertilizing in the irrigated furrow(AIFF) and alternate irrigation- fertilizing in the un-irrigated furrow(AIFU), AIFU is the best spatial coupling way, it has the highest yield and water use efficiency. (3) One reason why AIFU has the best spatial coupling effect is that it has a smaller evaporation area, thus its wate loss by this way is much smaller that traditional full irrigation; leching of fertilizer nutrients is much less than traditional irrigation because fertilizer and irrigating water exists in different furrows, the residual fertility exists in above 60 cm soil profile. (4) In AIFU, movement of water and fertilizer nutrients to the opposite furrow is very important to get a high yield and water use efficiency for this coupling way. (5) In AIFU, corn has longer root and higher root activity, and absorbs more nutrients, in later growing stage, corn leaves have higher content of chlorophyll and higher photosynthesis rate. The anti-drought enzymes also have a relatively high activity. This is another reason why this coupling way has higher yield and water use efficiency.(6) After harvest, AIFU has more residual nutrients above the layer of 60cm, it is benificial to improve the fertility of soil and has less pollution to under ground water and soil itself.We made new findings in following aspects:(1) We studied spatial coupling of water and fertilizer under unsufficient irrigation for the first time in the field of plant nutrition as we know, and applied it in semi-arid area, and studied its effect on corn plant yield and physiology. (2)The movement of soil moisture, soil nutrients, residue of soil nutrients and physiological changes under different coupling ways have been studied, thus we found the reason why different coupling ways have different water use efficiency and yield. (3) For the first time in the field of plant nutrition, we made the conclusion fo AIFU has more residual fertilizer nutrients in the lay of 40cm to 60cm in the soil profile, and it has less pollution to environment and can increase soil fertility.