| The Guanzhong irrigation district has sufficient light,heat,and water resources,and mainly implements a two-crop a year planting mode.Different stubbles in the multiple cropping system have different effects on soil,growth and yield of subsequent crops,at the same time,irrational application of nitrogen fertilizer in production in this area is widespread;rational application of nitrogen fertilizer according to different planting patterns is essential to ensure high yield of food crops and efficient use of resources in Guanzhong irrigation district.This study was based on the current situation of crop production in Guanzhong irrigation district,taking winter wheat as research object,setting two stubble types（maize stubble:M;soybean stubble:S）and three nitrogen fertilizer levels(high nitrogen:HN,225kg·hm-2;medium nitrogen:MN,180 kg·hm-2;low nitrogen:LN,135 kg·hm-2),to study the influence of stubble and nitrogen fertilizer on soil properties,winter wheat growth,physiological characteristics,grain-filling and yield,determine the suitable stubble and nitrogen application rate for winter wheat production in Guanzhong irrigation district,and provide a theoretical basis for the cultivation and management of winter wheat in Guanzhong irrigation district.Results were as follows:1.The content of soil available N content after winter wheat harvest under soybean stubble was significantly increased by 13.42%-27.18%compared with maize stubble;the MN treatment of soybean stubble and HN treatment of maize stubble had the highest available N content.The soil organic matter content under each stubble type decreased with the decrease of nitrogen application.The soil bulk density of the 20-40 cm soil layer was the largest,and the soil bulk density of soybean stubble was 2.22%-9.14%lower than that of maize stubble.2.The number of stems and tillers,dry matter accumulations,leaf area index,photosynthetic parameter value and chlorophyll content of winter wheat under soybean stubble increased compared with maize stubble,while the spike rate,harvest index,allocation proportion of dry matter in the spikes all decreased.soybean stubble is more conducive to the formation of plant photosynthetic products,and maize stubble is more conducive to the transformation of photosynthetic products.The MN treatment under soybean stubble performed best in the number of stems and tillers,dry matter accumulations,leaf area index,photosynthetic parameter value and chlorophyll content of winter wheat,and decreased with the decrease of nitrogen fertilizer under maize stubble.3.The grain-filling rules of different grain positions in winter wheat were consistent,the start of the grain filling,the final grain weight,the maximum filling rate,the average filling rate,and the active period of superior grains were greater than those of inferior grains.Grain filling was affected by nitrogen fertilizer,the final grain weight was the smallest in LN treatment,maximum filling rate and average filling rate were expressed as LN>HN>MN,initial filling potential,active filling period,and effective filling time decreased with the decrease of nitrogen fertilizer application,days achieving the maximal grain-filling rate increased with the decrease of nitrogen fertilizer application.The average filling rate of the three filling periods shown as LN>HN>MN,filling days and contribution rate in the early stage increased significantly with the decrease of nitrogen fertilizer application,filling days and contribution rate in the middle stage and late stages decreased with the decrease of nitrogen fertilizer application.2019-2020,the grain filling was still affected by stubbles,the final grain weight,days achieving the maximal grain-filling rate,the maximum filling rate and the average filling rate of superior and inferior grains shown as:maize stubble>soybean stubble,and the initial filling potential,the active filling period shown as:soybean stubble>maize stubble.The average filling rate of the three filling periods,filling days and contribution rate in the early stage of soybean stubble decreased,while filling days and contribution rate in the middle and late stages increased compared with maize stubble.4.Compared with maize stubble,the yield of winter wheat,number of spikes,and number of kernels per spike under soybean stubble increased 8.08%-12.52%,10.75%-26.31%,5.61%-9.74%,and the thousand-grain weight and harvest index decreased by 1.15%-2.06%,5.92%-9.51%,respectively.Under soybean stubble,MN treatment performed best in winter wheat yield and the number of spikes,under maize stubble,the yield of winter wheat in MN and LN treatments was significantly reduced by10.50%-15.90%compared with HN treatment,and the number of spikes decreased with the decrease of nitrogen application;MN treatment has the smallest thousand-grain weight under each stubble.Soybean can be used as a suitable stubble for winter wheat in Guanzhong irrigated district,and the moderate amount of nitrogen fertilizer(180 kg·hm-2)is the recommended amount of nitrogen for winter wheat production. |
