Studies On Coupling Effect Of Irrigation And Nitrogen Fertilizer Of High Quality Winter Wheat Clean Production

The studies were conducted from 2003 to 2004 on high-yield soil which returned the crop straw into soil annually at Qianzhuliu experiment site, Longkou, Shandong Province, P. R. China. JM20, typical cultivars of winter wheat with strong gluten potential used in local production were chosen in this study. The 15N isotope trace technique was applied in the experiment. From the view of soil-winter wheat plant system, the effects of different nitrogen application amount, fertilizer application method, irrigation frequncey, interaction of irrigation and nitrogen, on the the grain yield and quality of wheat were studied. Partitioning between wheat plant and soil , uptake, accumulation and utilization in wheat plant and losses of nitrogen in the system, and the distribution of NO3--N in 0-200cm soil profile were also investigated. The main results were as follows: 1. Effect of irrigation and nitrogen application on wheat grain yield The photosynthetic rate and transform efficiency and potential activity of light-energy in chlorophy PSâ…¡system of flag leaf after flowering were significantly promoted with increased irrigation frequency , supplying greater source for accumulation of dry matter. Weight per stem was slightly improved with adding irrigation times, but no significant diffenrences were found between treatments. Complete topdressing nitrogen evidently improved ФPSâ…¡and extented time of high value Fv/Fm of flag leaf after flowering. The kernel growth rate declined with adding irrigation frequency. Irrigation and nitrogen application properly could improve kernel number per spike and spike number per mu. Weight per 103 kernels declined with adding irrigation times. The effects of nitrogen and irrigation on yield was obvious. Grain yield shown tendency of increase-peak-decrease with adding irrigation and nitrogen application amount. Marginal effects of irrigation on yield was higher than that of nitrogen. Magrginal effects of irrigation on yield was highest when nitrogen application amount was lower, such as 1777.34kg/hm2/each time in non-nitrogen treatment. Magrginal effects of irrigation on yield declined with adding nitrogen application amout, and is rapidly decreasing with dding irrigation time, such as under zero value when nitrogen application amount was 240 kgN/hm2. Magrginal effects of nitrogen on yield declined with adding irrigation frequency and nitrogen application amount. Biological yield of irrigation treatments was higher than non-irrigation treatment, but no significant difference were observed between irrigation treatments. 2. Effect of irrigation and nitrogen application on wheat qulity Irrigation and nitrogen application had obvious effect on wheat grain protein content At maturity both kernel protein content and monomeric protein content of irrigation treatments were significantly lower than non-irrigation treatment. Insoluble glutenin content declined with adding irrigation frequency . Soluble glutenin content increased with adding irrigation frequency. Both kernel total protein content and protein compotents content of nitrogen application treatments were significantly higher than non-nitrogen treatment. Kernel protein content,soluble glutenin content,insoluble glutenin content of nitrogen complete topdressing treatment at the fertilizer level of 168 kgN/hm2 werehigher than split nitrogen treatment at both 168kgN/hm2 and 240kgN/hm2 fertilizer level. Kernel protein content,insoluble glutenin content,monomeric protein content of 240kgN/hm2 treatment were slightly higher than 168kgN/hm2 treatment. Soluble glutenin content and monomeric protein content consistently increased in the later stage of filling, and insoluble glutenin content increased slowly at the later phase of filling. Irrigation had evident effect on grain starch accumulation. Amylopectin content increased with adding irrigation frequency and amylose content declined with adding irrigation frequency. Nitrogen had no significant effect on grain starch acumulation. As showed by simulating formula of the effect of irrigation and nitrogen on dough stability time, effect of irrigation on dough stability time was significant and the negative magrginal effect of irrigation increased with the adding irrigation frequency. Effect of nitrogen application on dough stability time was not significant. Peak viscosity value and breakdown value of flour increased with adding irrigation frequency, and between nitrogen treatments there were no significant difference. Correlative analysis indicated flour protein content, Flour wet gluten content, monomeric protein content and insoluble glutenin content were positively correlated to dough stability time. Soluble glutenin content was negatively correlated to dough stability time. Amylopectin content was positively correlated to peak viscosity,breakdown. Amylopectin content was negatively correlated to pasting temperature. 3 Effect of irrigation and nitrogen fertilizer on absorption and utilization of nitrogen fertilizer In this experiment, the accumulation rate and the amount of nitrogen was highest from flaging to anthesis followed by that from anthesis to grain filling. Nitrogen accumulation rate and accumulation amount of irrigation treatments was significantly higher than non-irrigation treatment, and between irrigation treatments there were no significant difference. Nitrogen accumulation rate increased with increasing nitrogenapplication amount. Nitrogen accumulation amount and accumulation rate of nitrogen complete topdressing treatment at the fertilizer level of 168kgN/hm2 was higher than that of split nitrogen treatment at the fertilizer level of both 168kgN/hm2 and 240kgN/hm2. Fertilizer N recovery of irrigation treatments was significantly lower than that of non-irrigation treatment. Between irrigation treatments no significant difference were found. Fertilizer N recovery declined with increasing nitrogen application amount. Residul fertilizer N in soil declined with adding irrigation times and improved with nitrogen application amount. Fertilizer loss increased with adding irrigation frequency, and between nitrogen treatments there was no significant difference. The fertilizer N total recovery of complete topdressing treatment at the fertilizer level of 168kgN/hm2 was higher than that of split nitrogen treatment at the fertilizer level of 168kgN/hm2 and 240kgN/hm2. That was to say fertilizer N loss of nitrogen complete topdredding treatment was lowest among all N treatments. The proportion of nitrogen derived from topdressing fertilizer was higher than that from basal fertilizer in wheat plant. The ratio of nitrogen derived from fertilizer and total nitrogen uptake amount increased with adding nitrogen application amount. With non-irrigation treatment, the ratio mentioned above of nitrogen complete topdressing at the fertilizer level of 168kgN/hm2 was higher than that split nitrogen application at the fertilizer level of 240kgN/hm2. With the irrigation treatments, there were no significant difference between nitrogen complete topdressing treatment and split nitrogen treatments. At maturity, the proportion of nitrogen distribution in plants parts manifested grain>culm>leaf>chaff. The proportion of kernel nitrogen was three time of the vegetative nitrogen. Total nitrogen uptake amount and harvest index of irrigation treatments were higher than that of non-irrigation treatment, and between irrigation treatments there were no significant difference. Total nitrogen uptake amount increased with nitrogen application amount increasing, and nitrogen harvest index decreased withincreasing nitrogen application amount. Total nitrogen uptake amount and nitrogen harvest index of nitrogen complete topdressing treatment was higher than that split nitrogen treatment. As a result, on the fertile farmland, nitrogen fertilizer use efficiency declined with increasing nitrogen application amount. N fertilizer use efficiency of nitrogen complete topdressing treatment was higher than split nitrogent treatment. Nitrogen marginal benefit declined with increasing nitrogen application amount. But nitrogen marginal benefit of nitrogen complete topdressing treatment increased with adding irrigation frequency,. Nitrogen marginal benefit of split nitrogen treatment decreased with adding irrigation frequency. 4. Temporal and spacial changes in NO3--N content in 0-200cm soil profile In this experiment, NO₃--N accumulation amount in 100-200cm soil profile was significantly increased with increasing irrigation number and nitrogen application amount. NO3--N accumulation amount in 100-200cm soil profile of nitrogen complete topdressing treatment was lower than that split nitrogen treatment. Irrigation and nitrogen application at the later jointing when wheat absorbed NO3--N rapidly led to declined NO3--N leaching. At anthesis and before winter when the absorbing rate of nitrogen was lower, irrigation resulted in excessive NO3--N in 0-100cm soil profile and parts of NO3--N leaching to 100-200cm soil layer. The probability of NO3--N polluting groundwater was higher. 5. Ascertainment of the optimum irrigation and nitrogen application in wheat clean production The response of yield to irrigation and nitrogen fertilizer was increasing-peak-decreasing. The effect of Irrigation on dough stability time is the most negatively significant. Nitrogen complete topdressing treatment could get higher quality with no adding nitrogen application and less nitrogen fertilizer loss. Irrigation at jointing which was the period of the highest nitrogen absorbing rate and nitrogen complete topdressing...