The acidification due to organic matter accumulation (O[A.
It was considered that acidification due to biogeochemical cycles of elements other than C and N was negligible.
By difference between the total net acidification and the acidification attributed to the aforementioned components, the effect of nitrate leaching on soil acidification was estimated.
The effect of clover on soil acidification is highlighted in the literature (Ridley et al.
In the C cycle, while acids exudated by roots due to an excess of cation uptake over anions during plant growth are distributed in all soil layers explored by roots, plant residues are mainly oxidised at the soil surface, thus promoting acidification in subsoil and alkalinisation in topsoil.
Nitrogen mineral fertilisation and soil acidification
and, therefore, is acid in the short-term (Eqn 4), N added to the soil as urea or through biological fixation causes net acidification in medium- and long-terms only if there is N loss as nitrate leaching.
Mineral N application, in affecting soil acidification, also affected exchangeable A1 (Fig.
The net soil acidification is a function of the change in pH and the pH buffer capacity of the soil.
Net acidification occurred in all treatments, ranging from 20.
The acidification rates estimated in the present study are consistent with those usually observed in agricultural ecosystems, from 2 to 5 kmol [H.
The C cycle contributed to the soil acidification mainly via the removal of alkaline products from the field, through the harvest of maize grain, which was higher in leguminous-based cropping systems and in N-fertilised soils.
According to the model, alkalinisation occurred in soils where organic carbon stocks decreased (negative values in Table 3), mainly in the F/M system, while acidification occurred in soils where the stocks increased.