CROP PRODUCTIVITY OF WHEAT ROTATION SYSTE MS FOR 10-YEAR PERIOD, IN PASSO-FUNDO, RS, BRAZIL

From 1980 to 1989, the effect of crop rotation systems for wheat was a ssessed at the Centro Nacional de Pesquisa de Trigo (CNPT), in Passe F undo County, RS, Brazil. Four rotation systems for wheat were studied: system I (wheat/soybean); system II (wheat/soybean, rapeseed/soybean, barley/soybean, and white lupine or serradella/corn); system III(whea t/soybean, arrowleaf clover/arrowleaf clover, and arrowleaf clover/cor n, from 1980 to 1983, and wheat/soybean, white oats/soybean, and commo n vetch/corn, from 1984 to 1989); and system IV (wheat/soybean, rapese ed/soybean, flax/soybean, and white lupine or serradella/corn). A rand omized complete block design, with four replications and plots with 12 0 m(2), was used. Cultural productivity for that period, obtained by d ividing grain yield (kg/ha) of each species by the energy consumed, is presented in this paper. The energy consumed is the energy spent to p roduce a good or a service. The global analysis showed no difference a mong systems I (1.20 kg/Mcal), II (1.42 kg/Mcal), III (1.45 kg/Mcal), and IV (1.40 kg/Mcal). In the annual average the alternative systems I I, III and IV were five or more times higher than system I.