Construction And Simulation Of Crop Growth Model Based On Salt Ion Stress

In view of the problems of water shortage and serious soil salinization in Tianjin,this study took maize as the research object,and used a combination of field experiments and numerical simulations to set up different irrigation methods（conventional drip irrigation and under mulch drip irrigation）and irrigation quotas（10 mm and 20 mm）in Jinnan District,Tianjin in2017～2018 for field experiments,with a total of four treatments,namely N1（conventional drip irrigation 10 mm）,N2（conventional drip irrigation 20 mm）,M1（under mulch drip irrigation10 mm）and M2（under mulch drip irrigation 20 mm）,to explore the effects of different irrigation quotas on soil salt ion concentration,maize salt ion concentration,canopy coverage,biomass,yield and water use efficiency in Tianjin under conventional drip irrigation and under mulch drip irrigation,and to analyze the correlation between eight major salt ions,soil salt ions and maize salt ions and biomass in maize,and use the Aqua Crop model to simulate maize canopy coverage,biomass and yield in 2017 and 2018 under salt-free stress.The following research results were obtained by introducing the salt ion stress equation,constructing a crop growth model based on salt ion stress,and using the new model to simulate the maize canopy cover,biomass and yield in 2017 and 2018.（1）High water condition can reduce soil Ca²⁺,Mg²⁺,Na⁺,Cl^-,SO₄^2-and total salt concentration in the pre-growth period better than lower water condition;The relative amounts of soil anions and cations were the highest with HCO₃^-and Na⁺,and the lowest with CO₃^2-and Mg²⁺.High water and can increase the SO₄^2-and CO₃^2-concentrations in the pre-root growth period,Ca²⁺concentration in the middle growth period,SO₄^2-and CO₃^2-concentrations in the pre-growth stage of stems,CO₃^2-concentrations in the late growth period,Ca²⁺and K⁺concentrations in the pre-growth period of leaves,and can reduce the concentration of Na⁺and Cl^-in the pre-root growth period,the Na⁺concentration in the pre-growth and late stages of stem,the Na⁺concentration in the pre-growth period of leaves,and the Cl^-concentration in the middle stage of growth and CO₃^2-concentration in the post-growth period.The relative amounts of K⁺and Cl^-in maize rhizomes and leaves were the highest,and the relative amount of Na⁺in the roots was higher than that in the stems and leaves,and the relative amount of CO₃^2-in the leaves was higher than that in the rhizomes.There was a significant positive correlation between Ca²⁺and Mg²⁺,Na⁺and HCO₃^-in the whole maize plant,but negatively correlated with SO₄^2- in the whole plant.There was a significant positive correlation between whole plant K⁺ and whole plant total salt,and there was a significant positive correlation between whole plant Cland whole plant SO₄^2-.（2）High water and lower water could improve the Ca²⁺,Mg²⁺,K⁺,CO₃^2-and Cl^-qualities of rhizome in the early stage of rhizome growth,Ca²⁺,K⁺ and Mg²⁺ in the pre-growth stage of leaves.It can reduce the quality of Na⁺ in the early stage of root growth and SO₄^2-in the middle stage of growth,Na⁺ in the late stage of stem and leaf growth and SO₄^2-in the middle stage of stem growth.High water and lower water can improve canopy coverage in most of the growth period.Under conventional drip irrigation,high water and lower water could increase the biomass before the jointing stage of maize,while high water and lower water under submembrane drip irrigation conditions could increase the biomass before the filling stage of maize.The yield and water use efficiency under M2 treatment were the highest.There was a significant negative correlation between soil Mg²⁺,Na⁺,Cl^-and total salt concentrations and biomass,and soil HCO₃^-concentration and biomass were positively correlated.There was a significant negative correlation between K⁺ and total salt and biomass of whole maize plants under treatment.（3）Compared with the R² and EF values of the simulated canopy coverage of each treatment in 2017,the simulation accuracy of Aqua Crop without salt stress was improved by 1.14%～5.01% and 3.10%～16.18%,respectively,and the simulation error RMSE was reduced by 27.43%～66.13% compared with the simulation without salt stress.In the same year,the simulation accuracy of R² and EF without salt stress was increased by 0.06%～1.71% and 2.44%～10.80%,respectively,and the simulation error of RMSE without salt stress decreased by 31.28%～65.35%.In the same year,the simulated value of each treatment yield compared with the measured RMSE value,and the simulation error excluding salt stress decreased by 80.31%～90.57%.The simulation accuracy of the new crop model was improved by 0.03%～6.72% and 1.09%～19.06% compared with the R² and EF measured values of canopy coverage in 2018 compared with the measured values of Aqua Crop model without salt stress,and the simulation error of RMSE was reduced by 35.12%～79.33% compared with that without salt stress.In the same year,the R² and EF of the simulated and measured biomass values of each treatment were improved by 0.14%～3.06% and 3.24%～10.47% respectively,and the simulation error of RMSE without salt stress was reduced by 49.17%～70.13%.In the same year,the simulated value of each treatment yield and the measured RMSE value were reduced by 86.21%～93.24% compared with the simulation error without salt stress,so the crop model based on salt ion stress improved the simulation accuracy of Aqua Crop.The high water treatment reduced the soil Ca²⁺,Mg²⁺,Na⁺,Cl^-,SO₄^2-and total salt concentrations in the early stage of growth than low water treatment,and the leaching effect on the soil salt ion concentration in the late growth period was not significant.However,the effect of high water treatment and low water treatment on the concentration of salt ions in maize during the whole growth period was inconsistent.The high water treatment improved the canopy coverage and biomass before the jointing stage,and the water use efficiency under M2 treatment was the highest,and from the perspective of improving water use efficiency,submembrane drip irrigation 20 mm was the best irrigation scheme.From the correlation analysis between salt ions and biomass,it can be seen that soil Mg²⁺,Na⁺,Cl^-and total salt concentrations are significantly negatively correlated with biomass,soil HCO₃^-concentration is significantly positively correlated with biomass,while only K⁺ in the whole plant is significantly negatively correlated with biomass,indicating that soil Mg²⁺,Na⁺,Cl^-and HCO₃^-concentrations and K⁺ concentration of whole plants affect the accumulation of biomass.The new model has a good effect on the correction of 2017 and 2018,which can provide a certain theoretical basis for the research of salt ions and maize growth simulation in saline-alkali land in Tianjin.