EFFECT OF CROP-ROTATION ON GRAIN YIELD AN D ON THE SEVERITY OF WHEAT ROOT DISEASES, UNDER NO-TILLAGE SYSTEM

During five years, at the Cooperativa Agraria Mista Entre Rios Ltda., in Guarapuava, PR, Brazil, the effects of some crop rotation systems o n grain yield and on the severity of wheat root diseases were assessed . Four rotation systems for wheat were studied: 1) monoculture; 2) rot ation of one winter without wheat: 3) rotation of two winters without wheat; 4) rotation of three winters without wheat. A randomized comple te block design with four replications and plots with 60 m(2) was used . The severity of wheat root diseases in monoculture (33%), under no-t illage, was higher than the one found in rotation with one (12%), two (9%), and three winters wheat (11%).