Influence of soil moisture on hydrophobicity and water sorptivity of sandy soil no longer under agricultural use

Soil water repellency (SWR) is a dynamic property of soil that depends on a variety of factors. The warming of the climate and more frequent occurrence of droughts can both increase the SWR phenomenon. Land management demands that mitigation measures be continually adapted to strengthen the resilience of ecosystems and risk reduction strategies be refined. The aim of the work is to analyse the persistence and strength of SWR and soil moisture content (SMC) in sandy soil on abandoned agricultural land with a second succession of pine (S1), and in soil used for growing rye (S2). The studies cover the dry period from March 2019 to March 2020. Systematic measurements of SWR and SMC are carried out in two-week intervals for soil at depths of 0-0.05 and 0.35-0.40 m. For the top layer, the average SMC values for S1 and S2 are 7.18% and 11.21%, respectively. The field studies show a more substantial and longer-lasting repellency (extreme SWR classes occurred for 10 months) at the pine site than the studied phenomena in regions with a warmer climate. These studies make it possible to verify the dependence of SWR on SMC for both test sites, and excellent agreement is achieved between the critical SMC threshold for hydrophobicity determined in the laboratory and under field measurement conditions. Based on the indicated water and ethanol sorptivity, the average indices of hydrophobicity (R index) and their course in relation to SMC, are indicated. The average water sorptivity for S1 is 0.266 cm min(-0.5), for S2 is 0.383 cm min(-0.5). The average R index values are 31.91 and 3.97, respectively. These findings suggest that SWR may be a key soil property for identifying the occurrence of risk connected with the drying out of soil, especially in relation to a warming climate.