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.

Rainfall partitioning in young clonal plantations Eucalyptus species in a subtropical environment,and implications for water and forest management

Different canopy characteristics of industrial eucalyptus may lead to differences in water evaporation and availability to plants.This study aims to understand rainfall partitioning in a young clonal plantation(age of 2-4.5 years)of three eucalyptus species by relating tree parameters:diameter at breast height,total height,and leaf area index.We measured rainfall,throughfall,stemflow and litter interception,along with the tree parameters.The eucalyptus trees had rainfall interception varying between 22 mm(for 178 mm of rainfall)and 42 mm(for 87 mm of te rainfall),throughfall between 106 mm(for 186 mm of rainfall)and 44 mm(for 74 mm of rainfall),and stemflow between 0.5 mm(for 92 mm of rainfall)and 1.4 mm(for 24 mm of rainfall).For the three species,rainfall interception varied between 12 and 48%,throughfall between 57 and 90%,and stemflow between 0.3 and 5.4%.The coefficient of determination between interception and rainfall was 0.76,indicating interception depends on other variables,possibly including antecedent rainfall,rainfall intensity,and seasonality.Interception decreased with a reduction in leaf area index caused by eucalyptus defoliation.The E.benthamii had 0.75 mm of throughfall per 1 mm of rainfall,whereas in E.dunnii and E saligna,these ratios were 0.71 and 0.68,respectively.Stemflow in E.benthamii and E.dunii had a higher positive relationship with the diameter at breast height of the trees,whereas in E.saligna the highest relationship was with the rainfall.These results contribute to establishing management strategies,such as choosing suitable eucalyptus species to local climate,and to improve the synchronization of crop-demand versus soil-water-supply while maintaining streamflow to fulfill ecological and production needs.