| Furrow irrigation is a common irrigation technology used in middle-tillage crops,but the quality of irrigation is still the main problem.In order to further improve the quality of furrow irrigation,this paper,based on 45 groups of furrow irrigation experiments with tail closure in Guanzhong area of Shaanxi Province,adopts the technical route combining experimental research,theoretical analysis and numerical simulation to carry out the research on the combination optimization method of furrow irrigation management elements based on real-time feedback control,and achieves the following main achievements:(1)Based on the experimental data of field furrow irrigation,a reasonable collection range of data required for real-time management of furrow irrigation was proposed.The results show that,based on the data of water flow advancing process and water depth at the head of furrow collected at 0.6L and above,the soil characteristic parameters obtained by WinSRFR software can represent the actual situation of the whole furrow.The cumulative infiltration at the head of the furrow,water flow advancing process,water depth at the head of the furrow,irrigation quality index and irrigation amount simulated by using soil characteristic parameters obtained from inversion are basically consistent with the measured values.Except for the water depth at the head of the furrow,the mean relative absolute errors between simulated and measured values of other furrow irrigation process data are all less than 10%.(2)Based on Bayesian statistical method,a reasonable collection range of data sets that meet the requirements of different accuracy in real-time management of furrow irrigation was proposed theoretically.The results showed that,based on the data set collected by water flow advancing to 0.4L,0.5L,0.6L,0.7L and 0.8L,the mean relative absolute values of the simulated water advancing process and irrigation quality indexes were 24.65%,16.52%,9.93%,7.80%and 5.85%,respectively.In order to meet the requirement that the error between the simulated value and the measured value of the water flow advancing process and the irrigation quality index should not exceed 10%,the reasonable collection distance of the furrow irrigation data set(the water flow advancing process and the water depth at the head of the furrow)should not be less than 0.6L.(3)The effects of the three optimization strategies of technology elements were quantitatively compared on the improvement of furrow irrigation performance(Strategy 1:only optimize the cutoff time;Strategy 2:only optimize the inflow discharge;Strategy 3:simultaneously optimize the inflow discharge and cutoff time).The results showed that under strategy 3,Ea,Du and Es were increased by 18.1%,10.1%and 2.6%,respectively,compared with measured values.Strategy 1 and strategy 2 were followed,Ea,Du and Es increased by 12.4%,3.8%,0.5%and 6.1%,9.0%,0.4%,compared with the measured values,respectively.Strategy 3 is recommended barely from the perspective of improving irrigation performance,but strategy 1 is recommended when the practicability of the optimization strategy is considered at the same time.(4)The functional relationship between optimal irrigation time(Tcop)and the time required for water flow to 0.75L(T0.75L)was established,and a simplified estimation method of optimal irrigation time for the closed-end furrow irrigation was proposed.The results showed that under the circumstance of different soil infiltration capacities and the combinations of irrigation technique elements,Tcop and T0.75L can be characterized by a linear function,and the mean absolute percentage error is 19.75%between simulated values and estimated Tcop.The Tcop of strategy 1 and strategy 3 were estimated by T0.75L and the estimated results were essentially consistent with the simulation results by WinSRFR,the mean absolute percentage error of all furrow irrigation experiments were 16.22%and 14.40%,respectively.In addition,the estimated Tcop of strategy 1 and strategy 3 were used to simulated irrigation performance,the comprehensive irrigation performance indicator Y≥85.0%accounts for 75.6%and 92.7%of the effective furrow irrigation experiments,respectively,and which were obviously higher than the current condition(68.9%).This indicates that the method proposed in this study can reliably estimate the Tcop for the closed-end furrow irrigation,and can obtain higher irrigation quality. |
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