Study On Controlled Alternative Irrigation Technology And The Dynamic Simulation Of Water Transport In SPAC

Controlled Alternative Irrigation is an efficient irrigation method by alternately irrigating partial root zone,which is based on the theory of Water Deficiency.It can reduce irrigation water and transpiration without reduction in crop yield as well as increase water and nutrient use efficiency.There were a few of research on Controlled Alternative Irrigation,however,no research on the SPAC system water dynamic simulation has been conducted in Northeast.So, in this study,the experiment about soybean and maize under Controlled Alternative Irrigation were carried out in 2006 and 2008,meanwhile the SPAC water dynamic were carried out to service for the prediction of soil water movement and irrigaton at the Experimental Base of Water Conservancy College,ShenYang Agriculture University in 2008.Eventually these researching subjects provide a theory foundation for the popularization and application of Controlled Alternative Irrigation in ShenYang and Northeast region.The main research results are as followings:(1) For planting soybean,relative soil evaporation rate Es/E₀ has closely relationship with the surface soil water contentθand LAI.LAI is divided into four stages:LAI＜1,1＜LAI＜3, 3＜LAI＜4,LAI＞4,meanwhile,the relationship between Es/E₀ and surface soil water contentθare fitted under different treatments during the four stages.The results show that the relationships between Es/E₀ and surface soil water contentθare well fitted by linear function, the determinant coefficients are more than 0.705,as well as Regression equations are significant.Thus,the soil evaporation rate Es can be predicted by E₀,LAI,andθ,when the measurement data of Es in soybean field are lack.(2) The different treatments of Controlled Alternative Irrigation have different impacts on soybean growth,yield,water use efficiency and economic benefit.The study of soybean growth under Controlled Alternative Irrigation show that the soybean height and leaf growth of CAI2 are inhibited,but the speed soybean leaf senescence has not speed up,soybean pods per plant is not be affected,soybean pisolites per plant are at most.The study of yield water use efficiency and economic benefit under Controlled Alternative Irrigation show that the yield of CAI2 is highest,1.5%higher than EFI,and saving water 8.7%than EFI,the water use efficiency of CAI2 up to 1.14 kg/m³ is the highes,the economic benefit of treatment 2 is highest,9.7%higher than EFI.Compared with EFI,the CAI1 saves water 30.7%,the yield is 9.8%lower,the water use efficiency is 1.13 kg/m³,economic benefit is 16.7%lower.The water use efficiency of EFI is lowest,which is 1.03 kg/m³,yield and economic benefit of EFI is lower than CAI2.Therefore,CAI2 is the optimum irrigation scheduling.(3) For planting maize,relative soil evaporation rate Es/E₀ has closely relationship with the surface soil water contentθand LAI.LAI is divided into four stages:LAI＜1,1＜LAI＜3, 3＜LAI＜4,LAI＞4,meanwhile the relationship between Es/E₀ and surface soil water contentθwere fitted under different treatments during the four stages.The results show that the relationships between Es/E₀ and surface soil water contentθare well fitted by linear function, the determinant coefficient are more than 0.695,as well as Regression equations are significantly.Thus the linear equations can be used to determined boundary conditions that water transport simulation in SPAC under Controlled Alternative Irrigation.Meanwhile Es can be predicted easily by E₀,LAI andθ,when the measurement data of Es in soybean field are lack.(4) The different treatments of Controlled Alternative Irrigation have different impacts on maize growth,yield,water use efficiency,and economic benefit.The study of maize growth under Controlled Alternative Irrigation show that the maize height and leaf growth of CAI2 are inhibited,but the speed maize leaf senescence has not speed up,the ear is longest, the barren ear tip is shortest,the era girth is longest,the numbers of grain per ear is most,and the yield per plant is highest.The study of yield water use efficiency,and economic benefit under Controlled Alternative Irrigation show that the yield of CAI2 is highest,5.2%higher than EFI,and saving water 13.3%than EFI,the water use efficiency of CAI2 up to 3kg/m³ is the highest,the economic benefit of CAI2 is highest,20.0%higher than EFI.Compared with EFI,the CAI1 saves water 33.1%,the yield is 7.3%lower,the water use efficiency is 2.97 kg/m³,economic benefit is 6.6%lower.The water use efficiency of EFI is lowest,which is 2.22 kg/m³,yield and economic benefit of EFI is lower than CAI2.Therefore,CAI2 is the optimum irrigation scheduling.(5) The two-dimensional model of root water uptake was developed on the basis of the horizontal and vertical spatial distribution in the maize growth stages,which can reflect root density dynamic in the maize growth period with the correlation coefficients over 0.698.(6) The model of water transport in SPAC under the controlled alternative irrigation be used to simulate soil moisture changes during different growth stages of maize.The results show that simulated and measured values are significant correlation,slope coefficients are around to 1.0.According to the analysis of error the model has high precision before earring, the average absolute errors are 0.014cm³/cm³ to 0.015cm³/cm³,the average relative errors are 5.26%to 7.22%,mean square deviations are 0.029cm³/cm³ to 0.032 cm³/cm³.After earring, the maximum of average absolute error is up to 0.02cm³/cm³,the maximum of average relative error is up to 9.49cm³/cm³,the maximum of mean square deviation is up to 0.039 cm³/cm³,these errors are acceptable.Therefore,the model has high precision during different growth stages of maize,can be used to predict soil water movement serving for controlled alternative irrigation.