Geoderma Regional ( IF 4.1 ) Pub Date : 2020-04-19 , DOI: 10.1016/j.geodrs.2020.e00280 Tairone Paiva Leão , Bruna Freire Domingues da Costa , Vinicius Bof Bufon , Fermin Fidel Herrera Aragón
Water is a limiting factor in agricultural lands on tropical Savannas. Due to low rainfall and long periods of drought, irrigation becomes a critical factor for increasing productivity. In this scenario, improving irrigation management techniques is crucial for increasing water use efficiency. Soil water content sensors are important tools not only for soil-based irrigation scheduling, but also to calibrate weather-based irrigation scheduling. Time domain reflectometry (TDR) type sensors are an important tool for water content monitoring due to its potential accuracy, automation and real-time measurement capability. The objective of this study was to evaluate the TDR technique for the estimation of water content in five soils of the Brazilian savanna (two Oxisols, two Entisols and one Histosol) using polynomial, square root and logarithmic calibration equations. The influence of soil bulk density, organic matter and clay content, and presence of magnetic materials were also examined. Magnetic permeability was estimated from magnetic hysteresis curves for each soil. The equations were calibrated and validated on an independent data set. Validation was evaluated using the Coefficient of Determination (R2), Root Mean Squared Error (RMSE), Nash-Sutcliffe Efficiency and the RMSE to the standard deviation of observed data ratio. There was no benefit of including bulk density, clay content or organic matter on the calibration equations. The relative magnetic permeability was very close to one in all soils and thus did not influence the calibration. For the soils evaluated in this study a single logarithmic calibration equation calibrated for all samples was the best predictor of volumetric water content.
中文翻译:
使用时域反射仪估算巴西稀树草原下三个土壤阶的水分
水是热带稀树草原上农业用地的限制因素。由于降雨量少和长期干旱,灌溉成为提高生产力的关键因素。在这种情况下,改善灌溉管理技术对于提高用水效率至关重要。土壤含水量传感器不仅是基于土壤的灌溉计划的重要工具,而且对于校准基于天气的灌溉计划也是重要的工具。时域反射法(TDR)类型的传感器具有潜在的准确性,自动化和实时测量功能,因此是监测水含量的重要工具。这项研究的目的是使用多项式评估TDR技术,以估算巴西大草原的五种土壤(两种Oxisol,两种Entisol和一种Histosol)中的水分,平方根和对数校准方程式。还检查了土壤容重,有机物和粘土含量以及磁性材料的存在的影响。根据每种土壤的磁滞曲线估算磁导率。在独立的数据集上对方程进行了校准和验证。使用确定系数(R2),均方根误差(RMSE),纳什-苏克利夫效率和RMSE与观测数据比率的标准偏差。将体积密度,粘土含量或有机物包括在校准方程中没有好处。相对磁导率在所有土壤中都非常接近1,因此不影响校准。对于在本研究中评估的土壤,针对所有样品校准的单个对数校准方程式是体积水含量的最佳预测指标。