Long-, medium- and short-term dynamics of soil acidity in an integrated crop–livestock system under different grazing intensities

Abstract

Integrated crop–livestock systems (ICLS) are being highlighted as a sustainable way to produce food and increase the efficiency of land use. One of the important factors in this type of system is the impact of animals on soil acidity dynamics. Thus, the objective of the present study was to evaluate soil acidity dynamics over long- (11 years), medium- (3 years with semiannual evaluations) and short-term (6 months during pasture season) studies in an integrated soybean–beef cattle system exposed to different grazing intensities. An experiment was established in 2001 in a Rhodic Hapludox soil with a succession of soybean (summer) and a mix of black oat + Italian ryegrass (winter). Treatments consisted of different grazing intensities during the winter season: intensive grazing (IG), moderate grazing (MG), and no-grazing (NG). Soil was sampled at different times to evaluate the soil attributes related to acidity. The Ca and Mg budgets were also calculated for the long-term study. In general, the different grazing intensities in ICLS do not affect soil acidity dynamics. However, the presence of animals (ICLS with IG or MG) causes a decrease in the long-term soil acidification compared with NG. This is due to lower amounts of non-productive losses of Ca and Mg, which result in higher pH values and lower levels of Al saturation. The same trend is observed in the medium- and short-term studies: in most situations, the integrated system is less acidic, but the grazing intensity performed does not affect the soil acidity.