摘要
Environmental monitoring of small,rural watersheds was one of the components of the Natural Re-sources Management and Rural Poverty Alleviation Program(RS-Rural)in southern Brazil.The purpose of the monitoring was to assess the impact of promoting soil conservation and environment manage-ment practices adopted by farmers and funded by the Program.In four small monitored watersheds,in a total of 95 plots representing distinct land use and soil management,surface soil was collected to characterize ground-zero of the Program by determining several soil physical,chemical and microbio-logical properties.Principal component analysis(PCA)shows soil physical,chemical and biological properties were decisive in defining the agricultural soils in the rural watersheds with family farming.The sensitivity to chemical properties provides an opportunity to improve soil quality if soil management focuses on altering those properties.Soil management practiced by tobacco farmers leads to rapid,intense degradation of some natural soil properties,especially those related to the dynamics of soil organic matter,compared with more conservationist uses(forest,regrowth,and grassland).Thus,soil management must be reoriented to avoid the progress of degradation and recover soil physical and biological quality.Cover crops and by land-abandonment to allow natural vegetation are important management strategies for the degraded soils used for tobacco production,increasing soil organic matter,nutrients and microbial activity and thus allowing further crop production.In conclusion,wa-tersheds with tobacco cropping have soils with lower quality than when under no-tillage grain pro-duction,requiring changes in land use and soil management.
