Study On Population Growth And Yield Effect On Wheat/Maize Intercropping Under Different Nitrogen Application Levels

With the continuous increase of the world population,people’s demand for food is increasing,and the continuous progress of urbanization has led to the withdrawal of a large area of land from the scope of arable land,and the world food production is facing severe challenges.Therefore,how to produce more food on the limited arable land has become a key research topic for scholars at home and abroad.Intercropping not only has the advantage of increasing and stable yield,but also can promote the absorption and utilization of light,heat,water and nutrients and other resources,so as to increase the yield per unit area.Previous studies on intercropping were mostly focused on irrigation or supplementary irrigation,but there were few studies on the yield performance of intercropping population and the restoration of inferior crops under rain-fed conditions.The recovery growth of inferior crops in intercropping system has a direct effect on the yield of intercropping population.Therefore,it is necessary to study the recovery growth mechanism of inferior crops under rainfed conditions to provide a basis for reasonable intercropping and farmland nutrient management.In this paper,winter wheat/spring maize intercropping population was taken as the research object,and three nitrogen application levels N0,N1 and N2(corresponding to wheat0,120,240 kg ha^-1 and maize 0,180,360 kg ha^-1,respectively)were set and three cropping patterns（single cropping wheat,single cropping maize,wheat/maize intercropping）,using completely randomized block design,a total of 9 treatments were conducted to study the effects of different nitrogen application levels on the growth physiological characteristics,yield and yield components of wheat/maize intercropping population through two-year field experiments,to explore the growth recovery mechanism of intercropping maize,and to clarify the yield-increasing effect of intercropping maize.It provides a theoretical basis for promoting high and stable yield of intercropping pattern,optimizing planting structure and field nutrient management.The preliminary conclusions of this study are as follows:（1）The results showed that the plant height of different rows of wheat in each growth stage was the lowest in the side row,and the plant height in the harvest period in two years was lower than that of monoculture wheat,and there was no significant difference between other rows and monoculture wheat.The plant height of intercropping maize was lower than that of monoculture maize,and only showed a certain plant height advantage under N2treatment in 2020.Intercropping expert and side-row maize increased 1.50 cm and 2.61 cm respectively.During the whole growth period,the LAI and dry matter accumulation of intercropping wheat were higher than those of monoculture wheat,while the LAI and dry matter accumulation of intercropping maize were always lower than those of monoculture maize.（2）During the whole growth period,the leaf Pn of intercropping wheat in the first row of intercropping was significantly higher than that of single cropping,and the other rows were also higher than that of single cropping,but the difference was not significant.The SPAD value of wheat leaves was basically the same as that of Pn,and the flowering period of the first row was significantly higher than that of monoculture.The flowering period within two years was4.51%-9.52%higher than that of monoculture,and the other rows had no significant difference with single crop.However,in the competitive inferior position,the growth and development of intercropping maize was inhibited during the wheat/maize symbiotic period,so the Pn and SPAD values of intercropping maize were lower than those of monoculture maize,and the specific performance was monoculture>expert>side cropping.After wheat harvest,intercropping maize enters a separate growth stage.When the index was measured for the first time,the leaf Pn under N1 treatment was better than that of single cropping maize,and increased by 5.13%-11.92%compared with single cropping in two years.When the index was measured for the first time,the leaf Pn under N1 treatment was better than that of single cropping maize,and increased by 5.13%and 11.92%compared with single cropping in two years.Under N2 treatment,the Pn of border banks and professionals decreased by 3.77%and0.70%respectively compared with monoculture in 2020,and increased by 4.99%and 6.16%respectively compared with monoculture in 2021.The SPAD value of intercropping maize under N1 treatment was 5.76%-6.95%higher than that of monoculture,and the SPAD value of maize under N2 treatment was 4.80%-5.14%higher than that of monoculture.（3）The average two-year yield of the intercropping system increased by 6.80%,8.83%and 10.03%respectively compared with monoculture under N0,N1 and N2 treatments.Intercropping significantly increased the 1m long grain yield and yield components of wheat in the first row,and the spike number and 1m long grain yield in the second row were significantly higher than those in single cropping.Under the intercropping mode,maize showed a yield disadvantage,which decreased by 0.77%-5.32%compared with monoculture in two years.With the decrease of grain number per ear and 100-grain weight,the yield of side row was lower than that of single cropping,while the yield and its components of expert maize were higher than that of single cropping.Proper application of nitrogen fertilizer can weaken the edge disadvantage of intercropping maize.（4）In two years,the change ofΔWU of intercropping system relative to monoculture WU was less than 0,and reached the minimum value under N1 treatment,and reduced water consumption 21.20 mm and 18.59 mm respectively in two years.The maximum water use efficiency of each crop system appeared in wheat/maize intercropping under N1 treatment in two years,and it was 16.55 kg ha^-1 mm^-1 and 17.61 kg ha^-1 mm^-1 in 2020 and 2021,respectively.The change ofΔWUE of intercropping relative to monoculture WUE in two years is greater than 0,indicating that intercropping has obvious water use advantage compared with monoculture.The results of this study show that intercropping under rain-fed conditions has the advantages of yield increase and resource utilization.Driven by the fallow policy,the wheat/maize intercropping model can be properly developed in rain-fed areas to achieve the sustainable development of agricultural production.