How severe and subcritical water repellency determines the seasonal infiltration in natural and cultivated sandy soils

Abstract

Infiltration into meadow and fallow (cultivated) sandy soils was evaluated after several prolonged rainy and dry spells during the years 2005–2011. Both soils evolved on fluvio-eluvial sandy sediments planted with pine forest, were originally strongly water repellent, but their management after deforestation was different. The fallow soil was intensively cultivated since 1950 while the other was left for natural grassland succession. For comparison, the perfectly wettable bare sediment of similar origin and texture was taken as reference material.We focused on soil porosity, hydraulic conductivity (k(−20mm)) and sorptivity (S) estimated by mini-disc infiltrometer, water drop penetration time (WDPT), and water repellency index (R).The results indicate that cultivation (mainly liming) the fallow soil alleviated the water repellency to its subcritical level, what is also the main explanation for different water repellency persistence levels in fallow versus meadow soil. Notwithstanding, cultivation has not substantially increased water infiltration properties confirming the hypothesis that subcritical water repellency may still retard water infiltration. Some stability of wetting patterns observed in the meadow and fallow soils resulted in only insignificant increase of k(−20mm) during the rainy periods.Long dry spells enhanced the infiltration capacity in wettable reference material because of sorptivity increase. Sorptivities of water repellent meadow and fallow soils, however, remained restrained during both, the rainy and dry spells due to higher water content (when wet) and to stronger water repellency (when dry). As a result, only small seasonal variability in infiltration rates was observed in both water repellent soils.