Effects Of Intercropping And Combined Application Of Organic And Inorganic Fertilizers On Yield,Quality And Resource Utilization Of Forage Maize

Intercropping of cereals and legumes can efficiently utilize resources such as light,heat,water,and nutrients,thereby increasing crop yields and land utilization.However,significant amounts of chemical fertilizers are used in intercropping,which not only reduces fertilizer use efficiency but also causes environmental pollution.Combined application of organic and inorganic fertilizers can improve the soil environment and increase crop yield and quality.However,a suitable organic-inorganic fertilizer combination under cereal-legume intercropping in the Hexi region is still unclear.Therefore,field experiments were conducted in 2021 and 2022,with three planting methods and eight fertilization treatments to explore the effects of planting methods,fertilization treatments,and their interaction on the yield,quality,and resource utilization and to determine a suitable organic-inorganic fertilizer combination under maize/lablab intercropping system in the Hexi region.The planting methods include maize monoculture（M）,lablab monoculture（L）,and maize/lablab intercropping（I）,while the fertilization treatments were applied in each planting method,including F1:180 kg N hm^-2 organic fertilizer;F2:120 kg N hm^-2 inorganic fertilizer+60 kg N hm^-2organic fertilizer;F3:240 kg N hm^-2 inorganic fertilizer;F4:120 kg N hm^-2 inorganic fertilizer+120 kg N hm^-2 organic fertilizer;F5:120 kg N hm^-2 inorganic fertilizer+180 kg N hm^-2 organic fertilizer;F6:240 kg N hm^-2 inorganic fertilizer+60 kg N hm^-2organic fertilizer;F7:240 kg N hm^-2 inorganic fertilizer+120 kg N hm^-2 organic fertilizer;and F8:360 kg N hm^-2 inorganic fertilizer.This study will provide a theoretical and technical support for the sustainable development of maize in the region.The main research results are as follows:（1）Compared with monoculture maize,maize/lablab intercropping had no significant effect on the forage yield of maize,the total forage yield of the intercropping system was significantly increased due to the increase in the lablab yield.The two-year average fresh and dry forage yields were increased by 21.29%and 24.49%,compared to maize monoculture,respectively.Maize/lablab intercropping significantly increased the total crude protein content of the intercropping system,with an average increase of21.78%compared to monoculture.At the same time,intercropping promoted the crop water and nitrogen uptake and utilization,significantly increasing the nitrogen and water use efficiency（WUE）of crops.The two-year average land equivalent,water absorption,and nitrogen absorption ratios of the intercropping system were 1.50,1.40and 1.51,respectively,all greater than 1.These results indicate that maize/lablab intercropping can increase the total yield of the intercropping system,improve forage quality,promote the uptake and utilization of water and nitrogen by crops,and improve land productivity compared to maize monoculture.（2）Increasing nitrogen application can increase fresh and dry forage yield,crude protein,and starch of maize,lablab,and the intercropping system.F6 treatment significantly increased the fresh and dry forage yield,crude protein,and starch of maize,lablab,and the intercropping system.The two-year averaged total dry forage yield,crude protein yield,and starch yield with F6 treatment was increased by 53.72%,133.35%and 76.87%,compared to F1 treatment.In addition,F5,F6,F7 and F8 treatments did not show significant differences.Compared to F1 treatment,F6 treatment significantly increased the content of crude protein,starch,and crude fat of the intercropping system,as along with the relative feed value and grading index,but decreased the content of neutral detergent fiber and acid detergent fiber,and had no significant effect on crude ash.Increasing the nitrogen application rate could also increase water and nitrogen uptake and water use efficiency（WUE）in the intercropping system.Among all the treatments,F6 had the highest two-year average total water uptake,total nitrogen uptake,and WUE,which were 35.77%,112.44%and 51.38%higher than the F1treatment,respectively.However,the effects were not significantly different from that of F7 and F8 treatments.These results indicate that increasing nitrogen application rate can improve crop yield and quality,and promote crop water and nitrogen uptake,but continued application of nitrogen fertilizer beyond the optimal rate does not further increase crop water and nitrogen uptake and utilization.（3）Under the condition of intercropping maize and lablab,the F6 treatment resulted in the highest two-year average WUE water uptake and nitrogen uptake among all treatments.The F6 treatment also increased the forage yield and nutritional quality of the intercropping system,and achieved the best comprehensive results.Therefore,the combination of 240 kg N hm^-2 inorganic fertilizer and 60 kg N hm^-2 organic fertilizer is a suitable organic-inorganic fertilizer application strategy for the intercropping system of maize and lablab in the Hexi region.