Effects Of Maize And Potato Intercropping On Nitrogen Budget Of Farmland System Under Varying Nitrogen Levels

The nitrogen（N）budget of farmland ecosystem reflects the N source,input-output pathway,as well as surplus and loss status of the system.Research on the N balance of farmland ecosystems is conductive to clarifying N input,especially N fate and loss,and providing important theoretical basis for N management in farmland.However,there is less attention to the differences in N budget of agroecosystems under different cropping patterns.Based on field positioning experiment,this paper explored the N budget and impact factors of maize potato intercropping（I）under four N levels（no N application（N0）,conventional N application（N2）,1/2 conventional N application（N1）,and 3/2 conventional N application（N3））,and used maize monoculture（MM）and potato monoculture（MP）as controls,in order to provide a theoretical basis for N management under intercrop system.This study focused on analyzing the effects of maize potato intercropping on crop N uptake and utilization under varying N levels,together with the characteristics and regulatory factors of ammonia（NH₃）volatilization rate and accumulation.On this basis,the N mass balance method was used to calculate the N balance of the agroecosystemy.The main research results are as follows:（1）In comparison to the single cropping mode,the N uptake of maize and potato after intercropping was weak in the early growth stage,and rapidly increased in the middle and late stages,surpassing the corresponding monoculture.In comparison to the weighted average value of monoculture,intercropping significantly increased the N uptake during crop harvest and improved N use efficiency,with the most obvious advantage of intercropping at the N2 level.（2）The NH₃ volatilization rate increased with the increase of N application,and the ammonia volatilization rate of intercropping was lower than that of monoculture.In potato monoculture,maize monoculture and intercropping（I）,the NH₃volatilization accumulation accounted for 12.2-23.5%,8.7-16.3%,and 7.3-14.9%of the N application,respectively.Under varying N levels,In comparison to monoculture,intercropping reduced area-scaled NH₃ volatilization accumulation by19.2-25.0%and decreased yield-scaled NH₃ volatilization by 32.0%.（3）In the system total N input,the N application rate accounted for 66.82%in maize monoculture,59.55%in potato monoculture and 68.19%in intercropping,whereas N mineralization was highest in maize,followed by intercropping,and lowest in potato.In the system N output,the NH₃ volatilization occupied 8.6-15.3%,with maize monoculture being the highest,followed by potato monoculture,and intercropping has the lowest.Except for NH₃ volatilization,the other N loss was highest in maize monoculture,followed by intercropping,and lowest in potato monoculture.In comparison to monoculture,intercropping reduced total N loss by4.7-17.6%,with NH₃ volatilization decreased by 25.2-35.0%and other N losses reduced by 12.3-63.4%,the N loss significantly increases with the increase of N application.The average annual N surplus of intercropping was 26.37-36.35 kg·ha^-1,which basically maintained the balance of soil N pool,and the N surplus significantly increases with the increase of N application.In comparison to the weighted average value of monoculture,intercropping significantly lowered N surplus by 16.7-60.2%,and the degree of reduction decreased with the increase of N application rate.（4）As shown by related analysis,N application rate,NH₃ volatilization,N uptake,soil temperature,soil water content,soil p H,soil NH₄⁺-N and NO₃^--N content,soil bulk density and other factors were the main factors affecting N budget.As indicated by structural equation model（SEM）,N application rate,soil temperature and soil water content were the key factors determining N budget,and N application rate,soil temperature and soil water content indirectly regulated N budget by changing soil physical and chemical properties,NH₃ volatilization and N uptake.In conclusion,maize and potato intercropping with low N levels（N1）could increase N uptake,improve NUE,reduce N loss,and optimize crop system N budget in comparison to monoculture.Meanwhile,it is essential to consider reduced NH₃volatilization and balance the system N budget.To sum up,under reasonable N application rates,maize potato intercropping could enhance crop N uptake and reduced N fertilizer input,and effectively decrease N environmental losses,making it an efficient and environmental-friendly planting pattern.