墒情监测合理深度暨数据处理方法的探讨

Study on Reasonable Depth of Soil Moisture Monitoring and Data Processing Methods

【目的】农田土壤墒情监测的水分传感器埋设于耕作层,容易被机械破坏,而埋设过深则不利于反应耕层土壤含水率的动态,是墒情监测网点建设中的难题。【方法】通过进行农田0~70cm深度剖面水分的长期监测试验,分析了土壤剖面水分的特征和变化规律。【结果】不同深度处的土壤含水率对根系层或耕作层土壤平均含水率的代表性(数值和变化规律)差异明显,20 cm是关键深度,该深度的含水率与根系层(0~50 cm)平均含水率的相关系数最高(0.957),且能跟踪耕层土壤含水率的波动变化。依据单层土壤含水率实时数据的变化趋势进行根系层土壤含水率的反演,能显著提高30cm深度含水率与根系层含水率的相关系数(0.963)。依据水量平衡原理得出降雨情况下的根系层含水率反演算法,30cm以下土壤含水率高、变化波动小,对于捕捉根系层含水率的变化意义不大。【结论】综合考虑传感器埋设应避开耕作机械扰动深度的原则,推荐合理深度为28~30 cm。

【Objective】The moisture sensor for monitoring soil moisture in farmland is prone to be damaged by agricultural machinery in the tillage layer,but it is not conducive to reflect soil moisture dynamic of the tillage soil layer when the sensors are buried too deep.Therefore,this contradiction is a difficult problem for constructing monitoring moisture network.【Method】This study conducted a long-term monitoring experiment of soil water profiles along the depth of 0~70 cm and analyzed the characteristics and variation patterns of soil water profiles.【Result】Soil moisture at different depths varies significantly for the representativeness of the average soil moisture in the root or tillage layers.Here,the depth of 20 cm is the key depth.The correlation coefficient(0.957)between soil moisture at the depth of 20 cm and the average moisture of the root layer(0~50 cm)is the highest(0.957)and this depth could be employed to track the fluctuation of soil moisture in the tillage layer.The soil moisture in the root layer were inversed based on the trend of the real-time data of soil moisture in a single soil layer and this method significantly improved the correlation coefficient(0.963)between soil moisture at the depth of 30 cm and that of the root layer.In addition,the inversion algorithm of soil moisture in the root layer was obtained based on the water balance principle.High water content below 30 cm depth,with little variability,cannot be used to capture the variation of soil moisture in the root layer.【Conclusion】Considering the principle of avoiding the disturbance depth of farming machinery,the reasonable monitoring depth of soil moisture is recommended to be between 28 cm and 30 cm.