Spatial variability of thermal properties in relation to the application of selected soil-improving cropping systems (SICS) on sandy soil

Abstract

. The study aimed to determine the effect of randomly applied soil-improving cropping systems on the variability of soil thermal conductivity, heat capacity, and thermal diffusivity over the course of a 3-year (2016-2018) study. The field experiment included the control and the following soil-improving cropping systems: liming, leguminous catch crops for green manure, farm yard manure, and liming+leguminous catch crops+farmyard manure together with spring oats (2017) and spring wheat (2018). The parameters such as bulk density, water content, and values of soil thermal conductivity, heat capacity, and thermal diffusivity have been determined. The thermal properties were measured at the current water content in situ and in water-saturated and dry soil states in the laboratory. The thermal properties in the wet year of 2017 increased in the subareas with a predominance of leguminous catch crops for green manure, farmyard manure, and liming+leguminous catch crops+farmyard manure, whereas the soil-improving cropping systems effect was not consistent after stubble tilling in the dry year of 2018. Cross-semivariograms which used the sand content as an auxiliary variable and cokriging produced a better prediction than the semivariograms and kriging. The fractal analysis indicated that the number of subareas differing in thermal properties was mainly modified by water content and bulk density. The spatial spread of the soil thermal properties during the water-saturated and dry states increased in subareas with a higher bulk density.