Soil changes under different land-uses in the Cerrado of Mato Grosso, Brazil

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This study aimed to (1) examine the effects of land-use change on the soils of natural Cerrado transformed to common croplands (soybean/cotton/maize rotation and sugarcane) and pasture and (2) indicate how agricultural production affects water quality across a meso-scale catchment. Land conversion caused significant reduction in infiltration rates near the soil surface (0–40cm depth) of pasture (−96%) and croplands (−90% to −93%). Soil aggregate stability was significantly lower in croplands than in Cerrado and pasture. Topsoil pH and nutrient concentrations were high in croplands and pasture. Soybean crops had extremely high extractable P concentrations (80mg·kg−1; 9 times greater than the natural background), whereas pasture N levels declined. Nutrient accumulation of N and P did not occur at deeper horizons for any land-use type. Snapshot water sampling showed strong seasonality in water quality parameters. Higher temperature, oxi-reduction potential (ORP), NO2−, and very low oxygen concentrations (<5mg·l−1) and saturation (<60%) were recorded during the rainy season. In contrast, remarkably high (up to 0.8mg·l−1) PO43− concentrations were measured during summer. Water quality parameters were affected by agricultural activities at all sampled sub-catchments across the meso-scale catchment, regardless of stream characteristics (stream order, percentage of riparian vegetation, sub-catchment size); thus, no spatial trends were observed. Direct NO3− leaching appeared to play a minor role; however, water quality is affected by agricultural non-point sources, due to topsoil fertiliser inputs affecting the entire catchment, from small low order streams to the larger rivers of the modified catchment. In conclusion, land-use conversion has degraded soil physical properties, leaving cropland soils more susceptible to surface erosion with potential lateral nutrient transport to the stream network.