EFFECT OF CROP-ROTATION ON WHEAT IN NO-TI LLAGE SYSTEM, IN GUARAPUAVA, PR

From 1984 up to 1993, at the Cooperativa Agraria Mista Entre Rios Ltda ., Guarapuava, PR, Brazil, the effects of some crop rotation systems o n yield, control of root diseases, and other agronomic characteristics of wheat were assessed. Four rotation systems for wheat were studied: 1) monoculture; 2) one winter without wheat; 3) two winters without w heat; and 4) three winters without wheat. The crops grown in summer we re soybean or corn. Both winter and summer crops were grown under no-t illage, except in the winter of 1989, when limestone was applied befor e planting winter crops. A randomized complete block design, with four replications and plots with 60 m(2), was used. The crop rotation was efficient in controlling root diseases of wheat. Crop rotation of whea t under no-tillage controlled root diseases. Wheat grain yields decrea sed linearly as the severity of root diseases increased.