The effects of soil texture and Zytonic on accuracy of soil moisture measurement by time domain reflectometry method

Considering the increased interest in zytonic as a soil amendment, we evaluated the calibration method using direct gravimetric and indirect time domain reflectometry (TDR) for soil moisture measurements to improve TDR measurement accuracy underused zytonic and different soil types conditions. Three soil textures: silty clay, sandy loam, and clay loam as well as two levels of zytonic: 0 (control), and 1 (Kg m-2 zytonic) were considered under greenhouse conditions. The drawing of the coherence chart between the results of the TDR method and the volumetric method values showed that the highest and the least coincidence between the two methods were observed in clay loam + used zytonic (1.0 Kg.m-2 zytonic) (R2=0.98) and silty clay + control treatment (R2=0.87). The results showed that the TDR method has high accuracy for measuring soil water content in clay loam soils. Regression analysis between TDR-Volumetric water content (ϴTDR) and weighing method (ϴv) showed a good correlation with an R2 of 0.92 (silty clay+ zytonic), 0.96 (sandy loam+zytonic), and 0.98 (clay loam+zytonic). The results showed that increasing zytonic in soils increased the accuracy of the device in all of the studied soil textures. These results confirm the necessity of using soil properties for soil sensors like the TDR for estimating soil water content in different soil environments and also suggest that TDR sensors may provide an opportunity to improve soil moisture measurements in higher-clay-content soils.