Characterisation of soil organic matter in long-term fallow experiment with respect to the soil hydrophobicity and wettability

Abstract

Soil organic matter under different tillage and fertilisation systems of long-term fallow experiment established in 1958 in Prague was characterised in period of 1972-2004. This experiment consists of seven variants (control (no tillage, no manuring); farmyard manure compost (FYM); 2FYM; mineral fertilisation (NPK); 2NPK; reduced tillage (RT), and conventional tillage (CT)). In 1989, regular manuring and tillage were terminated and since then the plots have been maintained bare. Organic carbon content (Cox) was analysed and the hydrophobic (A) and hydrophilic (B) functional groups were determined using Fourier-transform infrared (FTIR) spectroscopy. Hydrophobicity index (HI) and soil wettability (A/B ratio) were assessed in the experimental variants. A high significant positive correlation (r = 0.976; P < 0.05) was found, between hydrophobic functional groups (Band A) and Cox, hydrophilic functional groups (Band B) did not correlate with Cox. Soil wettability tended to decrease after the organic manuring was finished with the result that the values of A/B ratio were significantly different according to the farmyard manure doses applied. On the contrary, HI responded to organic manuring termination later on and no significant differences were found between different farmyard manure doses. In the variants without any fertilisation, a continual decrease in both soil wettability and hydrophobicity during the selected time period was found; the degradation process is going on in these variants.