Effects Of Nitrogen Supply Level On Nutrient Uptake Rate And Productivity Stability In Maize And Soybean Intercropping System

The yield advantage of maize/soybean intercropping has been proved by a large number of experiments,but the effect of different nitrogen supply levels on the niche separation of growth rate and nutrient absorption rate of maize/soybean intercropping system and the effect on yield stability need further study.In this experiment,the split design was adopted.By setting four nitrogen supply levels,the Logistic equation was used to fit the growth parameters and nutrient absorption parameters of maize/soybean intercropping.The yield stability of the maize/soybean intercropping system under different nitrogen levels was statistically analyzed.Optimizing the fertilization of maize/soybean intercropping system provides a theoretical basis.Different nitrogen application rates have significant effects on the growth rate and parameters of maize/soybean intercropping.At NO(no nitrogen fertilizer),N1(180 kg/ha),N2(240 kg/ha)and N3(300 kg/ha)nitrogen supply levels,intercropping maize(N0I-M,N1I-M,N2I-M,N3I-M)The maximum biomass(K)and maximum growth rate(Imax)of monoculture maize(N0M-M,N1M-M,N2M-M,N3M-M)increased by 40.07%,12.40%,7.80%,8.31%,respectively And 62.57%,45.92%,30.44%,34.16%.On the contrary,for soybeans,as nitrogen levels increase,the K and Imax of intercropping soybeans(N0I-S,N1I-S,N2I-S,N3I-S)are higher than the corresponding monocropping soybeans(N0M-S,N1M-S,N2M-S,N3M-S)decreased by 27.44%,27.23%,26.72%,21.33%and 24.88%,22.01%,19.27%,13.66%.Under the same nitrogen application rate,the initial growth rate(r)of the corn and soybean intercropping treatments is higher than that of the corresponding monocropping treatment.The time to reach the maximum growth rate(tmax)of the intercropping soybean and intercropping maize is higher than that of the corresponding monocropping soybean and soybean.Single crop maize was advanced 4-6 d and 2-3 d respectively.Under different nitrogen supply levels,intercropping increased the maximum nitrogen uptake(NUmax-N),initial growth rate(r)and maximum nitrogen uptake rate(Imax)of maize,and decreased the NUmax-N value of intercropped soybeans.r value,Imax value.The NUmax-N value,r value,and Imax value of N2I-S treatment were reduced by 27.67%,5.74%,and 32.05%compared with the corresponding single crop soybean.The dynamic changes of phosphorus and potassium absorption of maize and soybean by nitrogen application rate and planting pattern are basically consistent with the law of nitrogen,and the application of nitrogen fertilizer during intercropping can increase the NUmax,r and Imax of maize,and the time of tmax appears earlier.Maize/soybean intercropping significantly increased crop yield stability,and appropriate nitrogen fertilizer application also promoted corn/soybean intercropping yield stability.At the same nitrogen level,the coefficient of variation(CV)of grain yield of intercropping maize was smaller than that of monocropping maize.From the average level,it can be seen that the CV value is the largest under NO treatment,which is significantly different from the other three nitrogen levels.Intercropping significantly increased the maize grain yield sustainability index(SYI).In this experiment,the N2I-M treatment had the highest SYI value and the highest yield stability.Under the same nitrogen application rate,intercropping reduced the grain yield of soybeans,and the grain yield of soybeans treated with N1I-S,N2I-S,and N3I-S decreased by 10.93%,11.22%,and 14.67%,respectively,compared with their corresponding single crops.For the coefficient of variation,the CV of intercropping soybeans is greater than that of monocropping soybeans at the same nitrogen level.From the average level,it can be seen that the CV value of soybeans differs significantly between each nitrogen level.The yield stability of maize/soybean intercropping system under different nitrogen supply levels was significantly affected by the amount of nitrogen applied.Under N2 treatment,the grain yield of the system was the smallest CV and the largest SYI,indicating that the intercropping system was the most stable.Maize/soybean intercropping increases soil fertility contribution rate and reduces fertilizer utilization.Maize grain yield increased by 36.29%,37.14%,and 29.55%compared to their corresponding monocultures when treated with N1I-M,N2I-M,and N3I-M,and treated with N1I-S,N2I-S,and N3I-S The yield of soybean grains was reduced by 10.93%,11.22%,and 14.67%compared to their corresponding monocultures,but the LER values of the four nitrogen application rates were all greater than 1,indicating that maize/soybean intercropping has obvious yield advantages.