Best management practices to reduce soil erosion and change water balance components in watersheds under grain and dairy production

Soil erosion and sedimentation are among the most serious global environmental problems. Soil and water conservation measures have been proven effective ways to reduce soil loss. The objective of this study was to evaluate the impact of three approaches of soil and water conservation measures (soil management, vegetative measures, and structural practices) on soil erosion and water balance of two paired agricultural watersheds located in Southern Brazil. Streamflow and sediment monitoring was carried out from 2016 to 2019 in the two small paired agricultural watersheds; called North watershed (NW) and South watershed (SW). Modeling using Soil & Water Assessment Tool (SWAT) was performed to simulate individual (nine scenarios) and combined (four scenarios) best management practices (BMPs), by including the three approaches. Among the nine individual BMP scenarios, the most effective in reducing soil erosion was crop rotation and cover crop (sediment yield, SY, reduction of 38.4 for NW, and 28.8% for SW). Among the four combined scenarios, the association of all conservation approaches was the most effective in reducing soil erosion (SY reduction of 46 for NW, and 41.5% for SW), followed by the vegetative measures scenario (SY reduction of 43.5 and 34.1% for NW and SW). All combined scenarios increased infiltration and subsurface water components, and decreased surface runoff. The findings of this study can help farmers and policymakers choosing appropriate BMPs to reduce current soil erosion problems and promote water and soil conservation.