Zhou Qingyun

Research on inversion of soil water dynamic parameters by field soil moisture content

The field soil moisture data under different vegetation and irrigation condition were accumulated by many irrigation experiments. The soil water dynamic parameters were acquired or improved by the parameters inversion method and making good use of these data. It was significance in monitoring and forecasting soil moisture and field water cycle. In this paper, according to the measured soil moisture of winter wheat from regreening to harvest in 2009 on Tianjin agricultural university agricultural water cycle experimental base, the parameter inversion model was established based on the objective function is the minimum of the relative error square sum between the simulated and measured value of the soil moisture content and the constraint is the diversification range of the water movement parameters acquired from the documents. The water transport parameters of soil characteristic in experimental site are acquired by use of the interior point method and model method. The results showed that the simulation accuracy of the field soil moisture dynamic is significantly improved by the parameter inversion. The changed initial value and step scaling factor are in favor of improving parameter optimization results.

Comparison of calculations for crop transpiration

It is significant to research crop evapotranspiration, including plant transpiration and soil evaporation, for field water cycle. There are some techniques to obtain transpiration index. In this paper, comparisons of three techniques for calculating evapotranspiration of grape under alternate partial root zone drip irrigation were curried. The results showed that cumulative transpiration can be calculated by sap flow and Penman-Monteith. Compare to water balance, the relative error was not beyond 10%. Considered the relationship of delay lag between the variety of sap flow of grape vine and the change of the transpiration, the modified coefficient K related with (Rn − G)was introduced. The results showed there was a good correlation between the modified temporal sap flow and the transpiration rate. The correlation coefficient is 0.8344, and the slop of correlation equation is 0.9038.