Study On The Influence Of Water And Fertilizer Integration On Soil Water And Fertilizer Distribution And Crop Yield Of Center Pivot Sprinkling Machine

This paper mainly explores the influence of the canopy interception of soybean on the water distribution of the center pivot sprinkling machine(CPSM),a popular irrigation equipment in Northeast China.The intercepted water volume was simulated by the Hoyningen-Braden method.During the experiments,the micro-sprinkling system(MSS)was incorporated into the CPSM,realizing three different fertilizing modes:MSS,CPSM,and MSS-CPSM.The three fertilizing methods were compared through experiments,which focuses on two widely planted crops in Northeast China:corn and soybean.The water volume intercepted by the canopy of each crop was analyzed in different growth stages.The continuous cropping system was contrasted with the rotation system at different irrigation volumes,fertilizing volumes,and fertilizing methods,revealing how the growth traits and yields of corn and soybean are affected by various fertigation modes.The relevant results help to improve the inefficient irrigation and fertilization,and mitigate the severe non-point source pollution of corn and soybean cultivation in Northeast China.In addition,the authors explored the influence of different irrigation volumes,fertilizing volumes,and fertigation modes on the growth and yield of corn and soybean,as well as the spatiotemporal distribution of water and fertilizer,in an attempt to optimize the irrigation volume,fertilizing volume,and fertigation mode.The main findings are as follows:(1)When the percentage of the CPSM 's walking speed is set 10%,20%……100%,a total of 10 levels,the canopy interception rate of soybean was 6.81%-16%,the water volume intercepted by the canopy of soybean peaked at 1.31 mm.For the CPSM,the sprinkler uniformity under the canopy averaged 87.1%in the circumferential direction,and 75.26%in the radial direction.When the CPSM operated at 30,60,and 90%speed,the sprinkler uniformities under the canopy were 5.62%higher than those above the canopy.According to the Hoyningen-Braden simulation of soybean canopy interception,the mean error(ME),coefficient of determination(R2),root mean squared error(RMSE),geometric mean of the error ratio(GMER),and geometric standard deviation of the error ratio(GSDER)were 0.041,0.958,0.082,1.024,and 1.103,respectively,an evidence to the high simulation accuracy of the model.(2)For the three fertigation modes,the fertilizer distribution and sprinkler uniformity were calculated and analyzed through tests at three different operating speeds.The results show that the sprinkler uniformities under CPSM-based mode,MSS-based mode,and CPSM-MSS-based mode were 91.50%,63.75%,and 80.20%,respectively.By the sprinkler uniformity,CPSM-based mode ranked the highest,followed in turn by CPSM-MSS-based mode,and MSS-based mode.As for the canopy fertilizer amount,CPSM-MSS-based mode had the lowest canopy fertilizer amount.(3)Maize and soybean,two widely planted crops in Northeast China,were subject to a two-year continuous cropping test at three different irrigation amounts,three different fertilizing volumes,and three different fertilizing modes.The test results show that:in the early growth stages,the growth traits of corn are significantly affected by irrigation amount:plant height,leaf area,and root length of corn all increased with the irrigation amount;in the later growth stages,the growth traits of corn are not significantly affected by irrigation amount.When the irrigation amount was 115.63mm,the top fertilizer amount was 114.75kg/hm2,and the top fertilizer method was CPSM-MSS-based mode,the partial productivity of corn yield and fertilizer was the maximum,and the maximum yield was 12807.22kg/hm2.For soybean,when the irrigation amount is 68.41mm,the topdressing amount is 9.75kg/hm2,and the fertilization method is CPSM-based mode,the yield reaches its maximum value,which is 2811.88kg/hm2.(4)Maize-soybean rotation system was implemented in 2018 and 2019.The two crops were separately tested by two-factor three-level design.For maize,when the fertilization mode CPSM-MSSbased mode,the topdressing was divided into two times before and after the jointing stage.Each time,the topdressing urea was 225kg/hm2 and potassium dihydrogen phosphate was 3kg/hm2,with the maximum yield of 16129.62kg/hm2.For soybean,the maximum yield was 3855.89 kg/hm2 when the fertilization method was CPSM-based mode,and the topdressing urea was 150kg/hm2 and 90kg/hm2 respectively at the branching stage and the initial flowering stage,and potassium dihydrogen phosphate was applied with 6kg/hm2.(5)The leaching of nitrate nitrogen can be avoided when the amount of nitrogen is small.As long as the fertilization amount is controlled within a certain range,the risk of nitrogen leaching can be avoided.Larger continuous rainfall and higher fertilizer application were the main factors that caused the leaching of soil nitrate into deep soil.The effect of water-fertilizer integrated fertilization on soil nitrate leaching was not obvious under different sprinkler irrigation conditions.