| Water and nitrogen fertilizer are two most important factors affecting the growth of maize.Summer maize in the Huang-Huai-Hai Plain is mainly ground-irrigated,with large irrigation quota,large amount of nitrogen,and low degree of water and fertilizer integration.Drip irrigation has a small irrigation quota and is easy to realize the simultaneous supply of water and fertilizer.However,information on the characteristics of water consumption and fertilizer requirements of summer maize under drip irrigation are limited.Two-year（2018-2019）field experiment were conducted to investigate the effects of various combinations of supplementary irrigation and nitrogen application on soil water and nitrogen distribution,growth index,physiological index,yield composition,water and nitrogen utilization efficiency of summer maize under drip irrigation.Irrigation treatments are recorded as W10,W20,W30,W40.Among them,the irrigation water amount was calculated from the relative soil water content in 010(W10),020(W20),030(W30)and 040 cm(W40)soil layer,the target relative soil water content at the corresponding soil depth after irrigation was100%of field water capacity.Nitrogen application rates were 0,120,180,240,300 kg/hm2,denoted as N0,N120,N180,N240,and N300,respectively)were applied.The period of N application was the same as irrigation,at the time of sowing and the beginning of the jointing and tasseling.Two years results show:（1）Under drip irrigation conditions,the characteristics of soil moisture and nitrate nitrogen distribution in 0100 cm soil layer under different water and nitrogen treatments in the same growth period were basically the same.With the increase of irrigation and nitrogen application,the water content of the 040 cm soil layer generally showed a decreasing trend,and the difference of the soil layer below 40 cm was small.The content of soil nitrate nitrogen increased with the increase in nitrogen application amount and decreased with the increase in irrigation amount.The soil moisture and nitrate nitrogen content of different treatments varied greatly in different growth periods.Among them,the soil moisture content and nitrate nitrogen content of 0-40 cm soil layer were the highest at the initial stage of jointing and the smallest at the maturity stage.When summer maize was harvested,the residual of nitrate nitrogen in the 0100 cm soil layer increased with the increase in nitrogen application amount and decreased with the increase in irrigation amount.Compared with W40 treatment,W10,W20and W30 treatments increased by 45.21%,33.73%and 20.90%,respectively.Similarly,compared with N300 treatment,N120,N180 and N24040 treatments were reduced by 30.42%,17.35%and 5.67%,respectively.（2）Growth indexes such as plant height,leaf area index,and above-ground dry matter of summer maize showed an increasing trend with the increase in irrigation and nitrogen application,but the raise declined after a certain limit is reached.It showed that the differences between N240 and N300 treatments under different irrigation treatments and W30and W40 treatments under different nitrogen treatment were not significant.The Logistic function can better simulate the dry matter accumulation process of summer maize under different water and nitrogen treatments.The results show that increasing irrigation and nitrogen application can increase the average growth rate and maximum growth rate of dry matter,but not conducive to extending the duration of the rapid accumulation period.（3）The chlorophyll content,photosynthetic rate,transpiration rate,and stomatal conductance of summer maize under W20 irrigation treatment increased with the increase of nitrogen application,but the increasing effect decreased after reaching a certain level.With the increase of nitrogen application,the PAR interception increased first and then decreased,and the PAR transmittance decreased first and then increased,both of which achieved extreme values at the N240 treatment.（4）Increasing irrigation and nitrogen application can increase summer maize grain yield,and the effect of nitrogen application on yield is greater than irrigation and water and nitrogen interaction.Compared with W40N300 treatment,W20N240（2018）and W20N180 treatment（2019）did not significantly reduce,but saved 20%to 40%of nitrogen application and reduced irrigation amount by 46.71%to 53.36%;compared with CK1,the yield was increased by0.74%5.22%,the amount of nitrogen applied was reduced by 20%40%,and the amount of irrigation was reduced by 33.36%45.51%.（5）Compared with W40N300,the water consumption of W20N240（2018）and W20N180（2019）is reduced by 17.39%18.16%,WUE and IWUE are increased by 14.40%16.39%and75.63%106.11%,NPFP and NAE increased by 20.17%55.98%and 67.84%,respectively.Compared with CK1,W20N240（2018）and W20N180（2019）treatments have reduced water consumption by 11.95%18.02%,WUE,IWUE and NPFP have increased by14.53%28.35%,51.18%108.10%and 31.52%67.90%.（6）Considering the irrigation water amount,nitrogen application,grain yield,water consumption,WUE,NAE and NPFP,it is suggested that water and fertilizer application scheme of summer maize under drip irrigation in the area should be as follows:the soil depth of supplementary irrigation was 020 cm,and the amount of nitrogen application was180240 kg/hm2.The periods of supplementary irrigation and nitrogen application were both sowing,jointing and tasseling.The upper limit of irrigation was the field water capacity,and sowing N:jointing N:tasseling N was 1:1:1.Sowing N was applied in basal,and jointing N and tasseling N were dissolved in water and then injected into drip irrigation system. |
