Study On Optimum Water-fertilizer Ratio And Yield Effect Of Summer Corn In Henan Province

Soil moisture and nutrients are not only the basic conditions for crop growth,but also the most critical controllable indicators during the growing period.Henan province is one of the main producing areas of corn and also an important producing area of agricultural products and grain in China,which plays a vital role in ensuring the national food security.However,unreasonable irrigation and fertilization during the growth period of summer corn will cause high consumption and low effectiveness.Therefore,seek a reasonable combination of water and fertilizer application,so that the crops achieve high yield and high efficiency,and provide reference for decision-making of summer corn water and fertilizer management in Henan Province.In order to make efficient use of agricultural water,in this study,three irrigation levels(80%fc,70%fc,60%fc)and three fertilization levels(216kg/hm2,180kg/hm2,114kg/hm2) were set for summer corn.Using irrigation and fertilization as experimental factors,the effects of different irrigation and fertilization levels on plant height,stem diameter,leaf area index,yield and water use efficiency of summer crop under inadequate irrigation conditions were systematically studied.At the same time,an optimization model was established with the goal of summer corn yield and water use efficiency,and used the multi-objective optimization genetic algorithm NSGA-Ⅱ to find the optimal combination of water and fertilizer.Finally,the Entropy-TOPSIS model was established to evaluate the advantages and disadvantages of summer maize water and fertilizer programs.The main conclusions of this study were as follows:(1)Irrigation and fertilization had significant effects on plant height,stem diameter and leaf area index of summer corn(P<0.01).With the increase of irrigation amount and fertilizer amount,the growth of plant morphology increased gradually.However,excessive application of water and fertilizer would result in leggy plants.With the development of the growth period,the growth rate of the morphological indexes of corn showed a trend of fast at first and then slow.The stem diameter and leaf area index decreased after the filling stage.At last,it was concluded that the the medium-water fertilizer(70%fc,180kg/hm2)environment was suitable for the growth of summer corn.(2)Taking irrigation and fertilization as independent variables and summer crop yield as dependent variables,the coupling model of water and fertilizer was established through binary quadratic regression fitting,and the regression model reached the significant level through detection.According to the model,single-factor effect analysis,marginal effect analysis and coupling effect analysis were carried out.It was found that the impact of water and fertilizer on maize yield was:irrigation amount>fertilization amount.Irrigation,fertilization and water fertilizer coupling had positive effects on corn yield.(3)The regression model of water use efficiency was established,and the model reached the significant level.The analysis showed that the water use efficiency showed a single-peak parabolic downward trend with the increase of two factors.The effect of irrigation amount on water use efficiency was greater than that of fertilizer application.Fertilization amount and the coupling of water and fertilizer had a positive effect on water use efficiency,while the irrigation amount had a negative effect on it.(4)Taking irrigation and fertilization as decision variables,an optimal model under the two-objective condition of corn yield and water use efficiency was established.The model was solved using Non-Dominated Sorted Genetic Algorithm-II(NSGA-II)to obtain the optimal water and fertilizer combination application:irrigation amount was 848.24m3/hm2,fertilization amount was 192.66kg/hm2.Under this combination,the maize yield was 10667.52kg/hm2,and the water utilization rate was 3.11kg/m3.(5)The evaluation model of Entropy-TOPSIS was established,and two first-class indexes of summer maize quality and benefit,five second-class indexes of plant height,leaf area,stem diameter,yield and water use efficiency were set up to construct the evaluation system of water and fertilizer scheme.The results showed that middle water fertilizer(70%fc,180kg/hm2)was the best scheme,and rain fed low fertilizer(0%fc,114kg/hm2)was the worst scheme.