TILLAGE EFFECTS ON SOIL PROPERTIES AND CROP PRODUCTION IN THE SUBHUMID AND SEMIARID ARGENTINEAN PAMPAS

Crops have been grown in the subhumid and semiarid Argentinean Pampas for over 50 years using tillage methods (intensive plowing) introduced from more humid regions. As a result, soil degradation due to erosion by wind and water has been moderate to severe. Experiments to control erosion through use of conservation systems were initiated at six sem iarid and subhumid sites in the Argentinean Pampas between 1976 and 19 90 and conducted for 5 to 11 years. In this paper, we summarize the ef fect of conventional and conservation tillage treatments on some soil properties and crop yields. Most soil physical, chemical, and biologic al properties were improved by conservation systems, but the rate of c hange differed due to climatic and soil differences among sites, with the difference due to tillage generally being greater at the more humi d sites with loamy soils than at the drier sites with sandier soils. C rops with a large N requirement yielded less with conservation than wi th conventional tillage systems. Use of conservation tillage can impro ve or stabilize soil conditions in the region, but crop nutrient requi rements must be met to achieve optimum crop yields when conservation t illage is used. Research regarding the plant nutrient requirements und er conservation tillage is being conducted. Also, conservation tillage is gaining acceptance in the Argentinean Pampas region. (C) 1998 Else vier Science B.V. All rights reserved.