NITROGEN AVAILABILITY AS AFFECTED BY 10 YEARS OF COVER CROP AND TILLAGE SYSTEMS IN SOUTHERN BRAZIL

Conservation tillage and cover crops are useful tools in Brazil for, r estoring degraded soils that resulted from the rapid expansion of agri culture without proper management during the 1970s. In 1985, a long-te rm study was initiated on a degraded Paleudult in the state of Rio Gra nde do Sul to better understand the impact of these soil management pr actices on nitrogen (N) dynamics in corn production systems. The syste ms include both conventional and no-tillage with oat/corn, vetch/corn and oat + vetch/corn, + cowpea (intensive). After nine years, no-tilla ge with the intensive cropping system resulted in a 24%, increase in s oil N ns compared to conventional tillage; there was no difference in corn yield between tillage systems.