ECONOMIC-ANALYSIS OF 4 CROP-ROTATION SYST EMS FOR WHEAT, OVER 10 YEARS, IN PASSO-FUNDO, RS

From 1980 to 1989, at the Centro Nacional de Pesquisa de Trigo, in Pas se Fundo, RS, Brazil, the effects of crop rotation systems on wheat we re assessed. Four rotation systems for wheat were studied: system I(wh eat/soybean); system II(wheat/soybean, rapeseed/soybean, barley/soybea n, legume/corn); system III(wheat/soybean, legume/legume and legume/co rn, from 1980 to 1983, and wheat/soybean, white oats/soybean and legum e/corn, from 1984 to 1989); and system IV (wheat/soybean, rapeseed/soy bean, flax/soybean and legume/corn). A randomized complete block desig n, with four replications and plots with 120 m(2) was used. Economic a nalysis on that period is presented in this paper. The mean net return of ten years of system II (US$ 302.22) was higher than that of system I (US$ 180.73). On the other hand, system IV (US% 293.95) was superio r to system III (US$ 186.56) and similar to system I.