Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/1996
Publication Date: N/A
Interpretive Summary: In Rio Grande do Sul and southern Parana, Brazil, researchers and farmers are firm believers in conservation tillage and winter cover crops. They credit conservation techniques with stabilization of soils in hilly to mountainous terrain. This benefits both farm and urban communities with reclaimed land, 30 percent increase in yield, clean water, and stable roads that had previously washed away with the rain. A group of U.S. scientists attended an international reduced tillage conference there and visited several research centers and farms to get a first hand look at the conservation successes in southern Brazil. Winter rain on bare fields caused the erosion and polluted streams. Cover crops reduced erosion. Conservation tillage increased cover crop effectiveness by decreasing the amount of time fields were without cover. Terraces, essentially berms every fifty feet on the contour, reduced slope length and held water for infiltration. Farmers in northern Parana had similar problems. The same conservation techniques did not work there because of different soil types and different crops like sugar and coffee requiring intensive management. Farmers in northern Parana continue to give conservation tillage a chance, but with caution and with some clean tillage. Information gathered by visiting researchers can help them assess conservation tillage in the U.S. and adapt it to marginal areas.
Technical Abstract: Six US scientists visited agricultural research sites and farms in southern Brazil. In Rio Grande do Sul and southern Parana, researchers and farmers believed in terracing, minimum tillage, and winter cover. They credited these conservation techniques with stabilization of soils in hilly to mountainous terrain. They claimed a better quality of life based on reclaimed land, increased yields, clean water, and stable roads. With 1600 mm of rain uniformly spaced throughout the year, winter fallow fields eroded. Erosion was reduced with winter cover crops. Minimum tillage management increased cover crop effectiveness. Terracing, often a berm every 10 to 30 m along the contour, helped by reducing slope length and increasing infiltration. Terraces interfere with normal farming operations since equipment cannot easily traverse them. Farmers either plant them in permanent cover or eliminate them after a few years and rely on cover crops to control erosion. Infiltration rates were 136 mm/hr for forests, 0.2 mm/hr for cropped fields, and 31.3 mm/hr for fields seven years in minimum till. Success in Rio Grande do Sul and southern Parana led farmers in northern Parana to try them. They had similar problems and plentiful rainfall, 1500 mm/year. These conservation techniques did not work because of different crops (more sugar cane and coffee, fewer corn and soybeans) and different soil types. Flocculate dispersion might be a problem in northern Parana but more study is needed.