Particle Size Distribution as a Basic Characteristic for Pedotransfer Prediction of Permanent Wilting Point

Abstract

The permanent wilting point (PWP) belongs to the basic soil hydrological constants and plays the important role in an estimation of the natural or irrigating moisture availability to agricultural plants. Direct measurement of hydrological parameters demands signifi cant amount of time, efforts and equipment. Pedotransfer functions (PTF) can provide an alternative way to an estimation of these parameters indirectly, by calculation, using accessible parameters of the basic soil properties in soil databases. Aim. To work out new PTF for an estimation of permanent wilting point in the chernozem soils of Ukraine. Methods. For the purpose of PTF working out, the multivariate linear regression equations have been applied. Data from the Ukrainian Soil Database are used for calibration of models sample included 239 data sets of permanent wilting point and particle size distribution (PSD) values obtained by direct measurement in the top genetic horizon of both typical and ordinary chernozems. Independently, 59 data sets have been used for verifi cation of models. Results. The best model among several considered has been recognized that one, where the contents’ parameters of three grain size fractions (according to N. A. Kachinskyi’s classifi cation) – 0.01−0.005, 0.005−0.001 and < 0.001 mm (%) – have been identifi ed as the essential independent variables. Thus, accuracy of the forecast (R 2 = 0.64) is quite admissible. Conclusions. Forecasting of permanent wilting point by construction of the pedotransfer function including three fractions of particles is tangibly possible, considering availability of PSD data in a soil database.