Nitrogen Fertilizer Operation And Utilization Difference Of Annual Soybean-Wheat And Maize-Wheat Under Low Nitrogen Input Of Single Season

This experiment was carried out in the experimental site of Shandong Agricultural University and the Key Laboratory of Crop Water Physiology and Drought-resistant Germplasm Improvement of the Agriculture Ministry from 2018 to 2019.In the crop rotation mode of soybean-wheat and maize-wheat,10 nitrogen application treatments were designed respectively:no nitrogen application?CK₀?;the nitrogen applications was 60 kg/hm²in the summer crops?soybean and maize?,and 60,120,180,240 and 300 kg/hm² in the wheat season,respectively;the nitrogen application was 60 kg/hm² in the wheat season,and 120,180,240 and 300 kg/hm² in the soybean and maize seasons,respectively.By comparing the growth and development of crop aboveground and the nutrient utilization of crop belowground under different nitrogen application of the two planting modes,the nutrient utilization efficiency of soybean and maize and its effect on the growth,development and nutrient utilization of wheat were discussed,and the nutrient utilization and economic benefits of the two planting modes were evaluated.After two years of experiment,the main mean results were as follows:1.Effects of nitrogen application on growth and yield of soybean-wheat and maize-wheat rotation modeThe number of pod per plant,seed per pod and yield of soybean increased first and then decreased with the nitrogen application amount,and reached the maximum when the nitrogen application amount was 240 kg/hm²,which increased by 17.1%,26.5%and 61.7%respectively compared with CK₀.The 100-grain weight showed an increasing trend with the increase of the nitrogen application amount.1000-grain weight and yield of maize increased first and then decreased with the increase of nitrogen application amount,and reached the highest at 240 kg/hm²,which increased by 17.9%,6.4%and 25.4%.The yield of the subsequent wheat increased with the increase of the nitrogen application amount of the previous summer crop.Compared with the wheat-to-corn rotation,the nitrogen content,dry matter quality and leaf area of the wheat plants in the latter rotation were higher than those in the soybean rotation,so the yield was higher.Moreover,the wheat yield difference between the two models was the largest when the nitrogen application amount of the summer crop was240 kg/hm².The number of ears,grains per ear,1000-grain weight and yield of wheat in rotation with soybean increased first and then decreased with the increase of nitrogen application amount.The 1000-grain weight reached the maximum at 120 kg/hm².The number of ears,grains per ear and yield reached the maximum at 240 kg/hm².Compared with wheat-corn rotation,the yield of the latter soybean and corn in wheat rotation increased with the increase of nitrogen application amount of the former wheat.Compared with wheat-corn rotation,the yield of the latter soybean in wheat rotation increased more due to its higher nitrogen content,dry matter accumulation and leaf area.2.Effects of nitrogen application on soil physical and chemical properties of soybean-wheat and maize-wheat rotation modesThe increase of nitrogen application not only improved the soil total nitrogen,but also promoted the utilization of soil organic matter,total phosphorus and total potassium.In the0-40 cm soil layer,compared with the maize completion stage,the soil nitrogen content,field water holding capacity and soil porosity in the soybean completion stage increased by 3.7%,13.4%and 4.6%,and the soil bulk density decreased by 7.8%,respectively,under the same nitrogen application amount,compared with the maize completion stage.Compared with CK₀,in the 0-20 cm soil layer,the nitrogen content increased by 23.2%and 22.7%,respectively.Compared with CK₀,in the 0-20 cm soil layer,the nitrogen content increased by 27.1%in soybean-wheat and 17.3%in maize-wheat,respectively.Under the condition of fixed nitrogen application in the last season,the utilization of soil organic matter,total phosphorus and total potassium increased with the increase of nitrogen application in the current season,and the contents of them decreased in the soil.3.Difference and economic benefit of annual nitrogen fertilizer utilization under two planting modesCompared with corn rotation wheat,wheat rotation with soybean had higher nitrogen utilization rate and partial productivity in season.Under the condition of fixed nitrogen application in summer crops,increasing nitrogen application in winter wheat made the nitrogen utilization rate of winter wheat increase first and then decrease,the nitrogen utilization rate was the highest in winter wheat when the nitrogen application was 240 kg/hm²The n use efficiency of winter wheat in rotation with soybean was 25.81%higher than that of winter wheat in rotation with corn.The nitrogen apparent balance of soybean-wheat rotation was higher,which was more conducive to soil sustainable utilization.At the same nitrogen application level,the yield of corn-wheat rotation was higher,but the profit of soy-wheat rotation was higher.In the treatment of fixing the amount of nitrogen applied to soybean and increasing the amount of nitrogen applied to wheat,the land equivalent ratio and yield of 60 kg/m² soybean nitrogen and 240 kg/hm² wheat nitrogen were the highest.In conclusion,the crop growth and soil quality in soybean-wheat rotation mode was superior than in maize-wheat rotation.In addition,when nitrogen was fixed in soybean and increased in wheat,the yield increase was greater.However,in order to amplify the differences in the experiment,the minimum nitrogen application amount of 60 kg/hm² was selected for the fixed nitrogen input,and the optimal annual nitrogen application amount combination may not be determined.This experiment can provide theoretical basis for follow-up research.