| Shouyang situated at the east edge of the Loess Plateau,most part of which belongs to the cinnamon soil district in eastern Shanxi.Agriculture in this area most rely on precipitation.Application of chemical fertilization was the main measurement for yield increasing.But unreasonable application of chemical fertilizers leads lower utilization rate of chemical fertilizers and benefits of fertilizers,resulted in certain environmental risks and even seriously damages the ecological environment.Straw is an important organic fertilizer.Continuous and efficient straw returning fertilization plays an important role for soil fertility,crop yield increasing and management of nutrient transformation,soil quality.Long-term localization experiment can reflect the effects of fertilization management on soil fertility and crop yield.Utilization of agricultural model technology based on long-term field trials could help for revealing the pattern of soil fertility and crop growth and yield changes under different management,as well as further understanding the quantitative relationships of crop growth and yield formation with soil,climate environments and management etc.,revealing the mechanism of soil nutrient cycle and providing theoretical basis for agriculture management.This study was conducted based on the long-term location experiment of dry farmland in Shouyang,Shanxi,which firstly including ajusting and verifying the DSSAT model to test its applicability in the study area mainly considering crop yield,biomass aboveground,and soil carbon and nitrogen nutrition variation.The verified model then was used to simulate crop yield and soil carbon and nitrogen nutrition variation under designed fertilization measurements of combinations of reduced fertilization and straw return measures,then the effect of different nitrogen fertilization and straw return measures on crop yield and soil carbon and nitrogen nutrition was analysed.According to this and optimize the fertilization scheme and a suitable combination was selected to achieve a satisfactory yield and soil fertility.This may help for providing a theoretical basis for sustainable agricultural management in this region.The results were shown as follows:(1)According to the verification results,using the adjusted spring maize parameters could simulate crop yield well,and reflect the difference among different fertilization treatments well with better consistency(with d value0.94、0.95、0.96、0.92 respectively for N1P1,N2P2,S3 and S5 treatments)and better simulation accuracy(with n-RMSE 14.46%、12.74%、12.21%、18.88% respectively for N1P1,N2P2,S3 and S5 treatments).A middle accuracy and better consistency to the measured data was obtained for aboveground biomass simulation by the adjusted model(with n-RMSE22.46%、23.11%、24.97%、27.62% respectively for N1P1,N2P2,S3 and S5 treatments and d value0.81、0.77、0.78、0.78).So the adjusted model could be used to evaluate varieties of corn grain yield,aboveground biomass in the study area.(2)According to the simulation results of soil organic carbon(SOC)and total nitrogen(TN)contents across 0-20 cm and 20-40 cm profile,the adjusted model could simulate SOC well.The simulation accuracy was better(with n-RMSE 12.57% and 17.44% for 0-20 cm and 20-40 cm profile),as well as better consistency to the measured data(R2=0.8279).The simulation accuracy of TN was lower(with n-RMSE 31.11% and 44.25% for 0-20 cm and 20-40 cm profile),but with a better consistency to the measured data(R2=0.8279).So the simulation effect of the adjusted model could be accepted for SOC and TN modeling,which could reflect the difference of SOC and TN between varied fertilization treatments.(3)According to the simulation results under designed reduced nitrogen application and straw return treatments,average yield and aboveground biomass for multiple years showed a similar tendency with different fertilization measures.At the same straw returning level,average yield and aboveground biomass for multiple years presented an increasing initially and then descending trend with the increasing nitrogen application.At the same nitrogen application level,the two indexes both increased with raisedreturning of straw.Compared with the peasant custom fertilization treatment(N4S0),most treatment demonstrated a higher yield and biomass except for N1S1 and N1S2 treatments.A higher partial productivity could be obtained under N1 level which declined with increasing nitrogen rate but affected weakly by straw returning rate.(4)According to the simulation results under designed reduced nitrogen application and straw return treatments,SOC and TN demonstrated a fluctuation changing trend along the fertilization years,and a similar deference with nitrogen and straw returning rates.SOC in 0-40 cm profile of N4S0 treatments decrease remarkably at the end of modeling period.TN in0-20 cm decreased by 7.5% and increased 1.6% in 20-40 cm profile than the initial value.At the same nitrogen rate,increasing straw returning could improve the SOC and TN in 0-20 cm profile.When the straw returning rate was up to 6000 kg/ha,SOC and TN IN 0-20 cm profile could maintain the balance with a small increasing comparing with the initial value.Straw returning improved the SOC and TN.Compared with peasants custom fertilization treatment,the computed relative increasing rate improved with increasing straw returning rate and relative increasing rates in 0-20 cm were higher than 20-40 cm profile.At the same straw returning rate,SOC and TN in 0-40 cm profile showed an unremarkably difference among different nitrogen rate treatments,and which could not be increased with increasing nitrogen rate.(5)Based on the modeling results,and considered crop yield,aboveground biomass,partial productivity for nitrogen fertilization,SOC and TN etc.,the fertilization measurement of N2S2(150 nitrogen rate and6000kg/ha straw returning rate,crushing and returning to the field)was a better and applicable fertilization mode for the study area,which could maintain a relative higher crop yield and soil fertility. |
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