Research On The Irrigation Forecast And Its Benefit Of Increasing Yield Under Limited Supply Water

The shortage of water resources makes irrigation water generally unable to meet crop growth.Therefore,limited water supply irrigation must be implement.Limited water supply irrigation means that the limited amount of water should irrigate to the period of the most sensitive to the formation of crop yields in order to obtain maximum yield and benefits.In view of this,in this paper,the spring wheat of Huoquan Irrigation Experimental Station in Linfen City,Shanxi Province,and the spring maize in Yangwu River Irrigation Experiment Station in Yuanping City were taken as the research object,and soil water,heat,and nitrogen transport conversion models were selected to measure the soil moisture content.Soil temperature and nitrogen were simulate.Through the optimization of the irrigation system in different typical years,the dynamic irrigation lower limit model was established,and the dynamic irrigation threshold value can used for irrigation forecasting and compared with the stimulation effect of empirical irrigation.The main results are as follows:(1)Using the irrigation test data of winter wheat and corn sow and spring maize for the period of 2015-2016,the parameters of soil moisture dynamic model and nitrogen transport model were determined and tested.The simulated value and measured value of the soil moisture content during the growth period of winter wheat and corn in the composite maize and spring maize had a good correlation,and the correlation coefficient R~2 reached more than0.7.For the nitrogen transport model of soil,the correlation between the measured values of nitrate-N in the 0-60cm soil layer and the simulated values is good,reaching 0.6 or more,and the content and measurement of nitrate nitrogen in the 0-60cm along the soil depth direction.The values are consistent.The above results show that the soil moisture and nitrogen transport model selected in this paper has good applicability.(2)The crop growth model was use to simulate the yield of winter wheat sow and spring corn.The results showed that the simulated grain yield had a good correlation with the measured yield,and the correlation coefficient R~2 reached more than 0.9.The selected P123crop growth model has a good applicability to simulated crop yield.(3)Based on the rainfall data from the Huoquan Irrigation Station and the Yangwu River Irrigation Experiment Station Series(1954-2015),different typical years have been determined,the division of different typical years was carried out and the optimization of the limited water supply irrigation system was carried out for different typical years.According to this,a dynamic irrigation lower limit model was established.The results showed that with the increase of irrigation volume,the yield increase benefit increased significantly,and,with the increase of precipitation,the irrigation water supply corresponding to the maximum increase in production benefit was significantly reduce.For the typical years of 75%and 95%,with the increase in the number of irrigation,the increase in production efficiency has increased significantly.In the more arid conditions,both the winter wheat in the dry period and the maize in the relatively abundant rainfall period all have greater stimulation effect.(4)Using dynamic irrigation limits to conduct irrigation forecasting,and compared with empirically irrigation,under the conditions of limited irrigation water supply,the benefits of forecasting irrigation are generally higher than empirical irrigation.The maximum increase rate of winter wheat complex sowing maize is 8.9%,the maximum benefit rate is up to 9.74%,the maximum increase rate of spring corn is 9%,and the maximum benefit rate is up to13.03%.This shows that irrigation by the dynamic irrigation limit value as the lower limit of irrigation can increase production and income.(5)The analysis results show that the reference crop evapotranspiration in the adjacent periods has a very good correlation and can reach extremely significant levels.When the period is ten days,the correlation coefficient R~2 can reach above 0.9.In view of this,during the irrigation forecast process,the value of meteorological elements in real-time monitoring was fully utilized and the correlation of reference crop evapotranspiration in adjacent periods is used to predict the reference crop evapotranspiration in the next 10 days,which is used to predict the actual evapotranspiration of crops.Due to the strong randomness of precipitation changes,the average daily precipitation over the past ten years was used as the forecast value of rainfall.(6)Analyze the prediction error of soil moisture content in farmland.The maximum relative error of soil moisture content for winter wheat in two seasons is 21.65%,the minimum value is 0.06%,and the average relative error is 7.95%.The maximum relative error of moisture content is 34.71%,the minimum value is 0.037%,and the average relative error is 6.25%.Both reached the level of A-level forecasting,indicating that the proposed forecasting method is reasonable and feasible.