Study On Simulation And Optimization Of Water And Nutrient Management On Potato

Potato is a staple food and cash crop to ensure food security and farmers’ continual income increase in China.It is very sensitive to soil water and fertilizer supply due to the shallow and loose distribution of roots,making potato water and fertilizer management more challenging.Unscientific water and fertilizer management is a key limiting factor in improving potato yield and the use efficiency of water and fertilizer,leading to imbalances in the atmosphere,water bodies,and soil ecology,and declining economic returns,which is detrimental to economic development and social stability.Therefore,it is imperative to optimize potato water and fertilizer management for synergy agronomic,economic and environmental effects.In this study,the northern mono-crop potato as the research object,based on the data of field verification experiment from 2017 to 2020 and the water and nitrogen(N)coupling field experiment from 2020 to 2021.Combined with Nutrient Expert(NE)system and crop models,sensitivity analysis,life cycle assessment,Technique for Order Preference by Similarity to Ideal Solution(TOPSIS)and Principal Component Analysis(PCA)were used to study the agronomic,economic and environmental effects of different water and fertilizer managements.We proposed agronomic and environmental N thresholds and optimized water and fertilizer management for potatoes.The main findings were as follows:1.Agronomic and environmental thresholds for N balance and N application in potato were proposed,and the synergistic effect of NE recommended fertilization on agronomy and environment were verified.Compared with farmers’ practice,NE treatment increased tuber yield,economic benefit and nutrient recovery by 7.2%,7.0%and 10.0 percentage points,respectively,and decreased N balance and loss by 48.3%and 31.1%,respectively.Compared with soil test fertilization,the N balance and loss of NE decreased by 26.9%and 13.4%,respectively.Through the regression analysis of N balance,N loss and N application rate,the thresholds of N balance and N application rate were 64.2-74.6 and 178.8-191.1 kg N/ha,respectively.The N balance(51.8 kg N/ha)of NE was lower than the thresholds,indicating that NE could improve tuber yield and agronomic efficiency,as well as reduce the risk of environmental pollution.2.Field management for increasing tuber yield and agronomic efficiency was initially explored.DNDC(DeNitrification-DeComposition)and WHCNS_Veg(soil Water Heat Carbon Nitrogen Simulator of Vegetable)models could well simulate the tuber yield,N uptake,and soil temperature and moisture.Parameterized models were used for sensitivity analysis,which showed that the N fertilization rate,timing,ratio and depth,planting date and density affected tuber yield and N use efficiency.We suggested that the N fertilization rate,depth,planting density and date were 150-180 kg N/ha,15-25 cm,5-6 seeds/m2 and April 25 to May 10,respectively,for potato-producing area of the agro-pastoral ecotone in the northern of Yinshan Mountain.Compared with the baseline scenario,the tuber yield and N recovery efficiency of optimized management increased by 1.1%-3.0%and 7.3-16.0 percentage points,respectively.3.The water and N coupling effects on potato growth,yield composition,tuber quality,water and N use efficiency and profit were clarified.Water and N application had significant effects on agronomic efficiency and economic benefit of potato,and the water effect was greater than that of N-application.Compared with empirical irrigation,the optimized irrigation decreased water amount by 20.9%,and the yield,profit and water use efficiency increased by 2.9%,8.4%and 12.2%,respectively.Compared with 100%chemical N fertilization,25%organic N substitution increased tuber yield,profit and N recovery efficiency by 9.4%,13.8%and 4.0%,respectively.Moreover,25%organic substitution offset the proteinreduction effect of irrigated water.The comprehensive assessment results showed that the coupling treatment of optimized irrigation and 25%organic N substitution was an optimized water and fertilizer management practice to improve agricultural efficiency and economic benefits.4.The water and N coupling effect on potato soil reactive N(Nr)loss and greenhouse gas(GHG)emissions were clarified,and the carbon and N footprint of potato production system was quantified.Water and N application had significant effects on Nr loss,GHG emission and the footprint of carbon and nitrogen in potato production system.Compared with empirical irrigation,optimized irrigation increased Nr loss and N footprint by 1.2%and 1.2%,and decreased GHG emission and carbon footprint by 8.3%and 9.2%.Compared with 100%chemical N fertilization,25%organic N substitution decreased Nr loss and N footprint by 11.0%and 10.2%,and decreased GHG emission and carbon footprint by 8.5%and 10.4%.Except for the without N application treatments,the treatment of empirical irrigation combined with 25%organic N substitution had the lowest Nr loss and N footprint,which were 61.8 kg N/ha and 1.8 kg N/t,respectively.The treatment optimized irrigation combined with 25%organic N substitution had the lowest GHG emission and carbon footprint,which was 3758.6 kg CO2 eq/ha and 108.9 kg CO2 eq/t,respectively.5.The variation rules of tuber yield and carbon-nitrogen emissions under different water amounts,N rates,and organic substitution ratios were revealed,and the optimized water and fertilizer management practice that synergized agronomic,economic and environmental effects were proposed.DNDC could well simulate tuber yield,N uptake,evapotranspiration,and Nr loss under irrigated and N-applied conditions.The effect of water amount on yield and soil Nr loss was greater than that of the N rate and organic substitution ratio.With the increase of N application rate,tuber yield increased then flattened,Nr loss increased exponentially,and carbon footprint decreased first and then increased.With the increase of organic substitution ratio,tuber yield and Nr loss decreased,and carbon footprint increased.The optimal water and N management practices were W80 irrigation(132 mm)and 10%-20%organic substitution ratio under 180 kg N/ha fertilization.Compared with the W100 irrigation and 25%organic substitution ratio under 210 kg N/ha fertilization,the tuber yield increased by 14.0%,and the N footprint and carbon footprint decreased by 7.7%and 34.7%,respectively.In summary,optimized water and fertilizer management could improve tuber yield,water and fertilizer use efficiency and economic benefits,while reducing carbon and nitrogen emissions.The water and fertilizer management practices with synergistic agronomic,economic and environmental effects proposed in this study were conducive to clean,efficient and sustainable potato production.