| The Guanzhong Irrigation District is a major winter wheat production area in Shanxi Province,where winter wheat is often planted in rotation with summer sown crops to achieve biannual maturity.Thus,achieving high yields of winter wheat in this area is of great importance to ensure grain production in Shaanxi Province.However,in wheat production,lodging is an important obstacle to achieving high and stable yields.Therefore,in order to achieve a good and stable yield of wheat and increase farmers’income,two stubble types（maize stubble:M;soybean stubble:S）and three nitrogen fertilizer levels(high nitrogen:HN,225 kg N·hm-2;medium nitrogen:MN,180 kg N·hm-2;low nitrogen:LN,135 kg N·hm-2)were used to study the ability of winter wheat to resist overwhelm under different stubble and nitrogen fertilizer levels,specifically to identify the effects of their interaction on wheat growth,stem physical characteristics,mechanical properties,physiological indexes,yield and yield components.The main purpose was to make sure which stubble and nitrogen application rates were appropriate for winter wheat production in the Guanzhong irrigation area.Besides,this paper also aims to provide a theoretical foundation for improving the cultivation and management of winter wheat in the Guanzhong irrigation area.The main results are as follows:（1）This study found that compared with before winter wheat sowing,the content of soil total nitrogen,organic matter,and available phosphorus in mature wheat fields decreased significantly by 2.10%-19.47%,7.39%-19.31%,and 3.91%-22.89%,respectively,while soil p H increased significantly by 0.04-0.31.Compared with maize stubble,soil total nitrogen,organic matter,and available phosphorus under soybean stubble increased significantly by 3.28%-26.08%,5.30%-32.10%,and 16.04%-54.75%,respectively,while soil p H decreased significantly by 0.13-0.41,and soil bulk density decreased significantly by 2.30%-9.64%.Under soybean stubble,the soil total nitrogen content of the MN treatment was significantly higher than that of the HN treatment and LN treatment,increasing by 5.40%-16.08%.The soil p H of the HN treatment was significantly higher than that of the MN treatment and LN treatment,increasing by 0.04-0.13.Under maize stubble,the soil total nitrogen content of the HN treatment was significantly higher than that of the MN treatment and LN treatment,increasing by 2.54%-12.10%,and the organic matter content was significantly higher than that of the MN treatment and LN treatment,increasing by 8.47%-18.24%.The soil p H of the HN treatment was significantly higher than that of the MN treatment and LN treatment,increasing by 0.04-0.10.Overall,compared with maize stubble,soybean stubble can improve soil fertility and nutrient levels.（2）The results of this study showed that,compared with maize stubble,the stem length,stem wall thickness and diameter of the three internodes at the base of soybean stubble increased significantly by 0.68%-5.70%,1.35%-12.75%and 1.09%-5.90%,respectively,and the number and area of the large and small vascular bundles at the second internode of the base increased significantly.Compared with maize stubbles,hemicelluloses and lignin contents in the second internode at the base of winter wheat stem significantly increased by 8.42%-18.46%and 5.31%-19.08%,respectively,under soybean stubble.The activities of PAL,TAL and POD were significantly increased by 2.42%-22.89%,2.05%-48.02%and 2.03%-11.45%,respectively.In general,soybean stubble is beneficial to increase the stem diameter,improve the stalk enrichment,and significantly increase the stalk bending resistance and lodging resistance index by 1.49%-6.61%and6.95%-15.20%compared with maize stubble,respectively,which can significantly reduce the population lodging rate of winter wheat.Under both stubble conditions,the contents of cellulose,hemicellulose and lignin in the second internode at the base of winter wheat treated with MN were significantly higher than those treated with HN and LN,and the activities of key enzymes for the synthesis of PAL,TAL and CAD were significantly higher.MN treatment was also beneficial to increase the thickness and diameter of stem wall at the base of three internodes of winter wheat,as well as the number and area of large and small vascular bundles.The results showed that the bending resistance of stem and lodging resistance index of stem were enhanced and lodging rate of winter wheat population was decreased.（3）The results showed that compared with maize stubble,soybean stubble could promote tillering,increase tiller number,flag leaf SPAD,LAI and above-ground dry matter accumulation of winter wheat,but reduce the heading rate.Compared with maize stubble,although soybean stubble significantly reduced the 1000-grain weight and harvest index of winter wheat by 4.61-12.28%and 4.14%-9.28%,respectively,it significantly increased the number of spikes and grains per spike by 2.41%-32.48%and 5.26%-8.70%,and finally increased the yield by 10.42%-35.81%.SPAD,spike number,grain number per spike,1000-grain weight,yield and harvest index of winter wheat under soybean stubble MN treatment were the best,but LAI and above-ground dry matter accumulation under HN treatment were the best.SPAD,grain number per ear,1000-grain weight,yield and harvest index of winter wheat under MN treatment were the best,but leaf area index,above-ground dry matter accumulation,and ear number under HN treatment were the best.In general,compared with maize stubble,soybean stubble is more conducive to winter wheat growth and increase winter wheat yield.The MN treatment under both stubble types is more beneficial for the growth of wheat,increasing winter wheat yield.Therefore,in Guanzhong irrigation area,soybean can be used as a suitable stubbly for winter wheat,and 180 kg N·hm-2nitrogen is applied in winter wheat season.This combination can not only improve soil fertility and reduce the risk of stalk collapse of winter wheat,but also maintain a stable yield,which is more suitable for winter wheat production in Guanzhong irrigation area. |
