Soil quality under native, agricultural and silvopastoral systems in Mollisols the semiarid Chaco Region, Argentina

Abstract

Over the last forty years, the semi-arid Chaco landscape has increasingly undergone changes driven by forest-clearing, expansion of agricultural areas, intensive farming, and livestock-grazing in forest areas. Knowing the impact on soil quality was necessary and important to implement agricultural policies under a sustainability paradigm. The objectives were i) to evaluate how forest-clearing and agricultural and silvopastoral use affect soil quality in Mollisols of Chaco; (ii) to establish reference values for high soil quality; and (iii) to correlate chemical quality with a physical quality indicator. A completely randomized sampling design was used, with three treatments: forest (MON), silvopastoral system or forestry-livestock (FG), and no-till agricultural system (SD). Nine batches were selected per treatment and sampled at 0-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.30 m. The following indicators were determined: texture, pH, electrical conductivity, organic matter, effective cation exchange capacity, exchangeable cations, and aggregate stability (EA). The following indices were calculated: saturation percentage of each exchangeable cation, relative stability index and chemical quality indices. An ANOVA, LSD test, and single and multiple correlations were performed. High-quality reference values were determined (MON). The indicators and indices showed that land-use had a negative effect on soil chemical and physical quality. Even though SD and FG resulted in soil fertility loss, the relationships between cations indicated that there was no deficiency or imbalance of nutrients; they should be included in the set to monitor the systems in this type of soil and systems. The physical quality (EA) was associated with the chemical quality of the soil.