ECONOMIC ANALYSIS OF CROP ROTATION SYSTEMS FOR THE PLANALTO MÉDIO OF RIO GRANDE DO SUL STATE | ANÁLISE ECONÔMICA DE SISTEMAS DE ROTAÇÃO DE CULTURAS PARA A REGIÃO DO PLANALTO MÉDIO DO RIO GRANDE DO SUL

English. During nine years the economic effects of seven c rop rotation systems were assessed. The following systems were evaluated: system I (wheat/ soybean); system II (wheat/soybean. from 1987 to 1989, and wheat/ soybean and common vetch/corn, from 1990 to 1995); system III (wheat/soybean, black oats or white oats/soybean, and common vetch/corn); system 1V (wheat/soybean, white oats/soybean, flax/soybean, and common vetch/corn, from 1987 to 1989, and wheat/soybean, sunflower or black oats/soybean, white oats/soybean, and common vetch/ corri, from 1990 to 1995); system V (wheat/soybean, wheat/soybean, black oats or white oats/soybean, and common vetch/corn); system VI (wheat/soybean, wheat/soybean, white oats/soybean, flax/soybean, and common vetch/ com, from 1987 to 1989, and wheat/soybean, wheat/soybean, sunflower or black oats/soybean, white oats/soybean, and common vetch/corn, from 1990 to 1995); and system VII (winter fallow/soybean, from 1990 to 1995). In the mean from 1987 to 1989, systems IV and VI showed h igher net returns than systems III and V, respectively. In the average from 1990 to 1995, no si gni ficant differences were observed for net return in Ihe systems evaluated.

Portuguese. Durante nove anos, foi conduzido um experimento com sete sistemas de rotação de culturas, os quais foram avaliados quanto ao aspecto econômico. Os tratamentos foram constituídos por: sistema I (trigo/soja); sistema II (trigo/soja, de 1987 a 1989, e trigo/soja e ervilhaca/milho, de 1990 a 1995); sistema III (trigo/soja, aveia preta ou aveia branca/soja e ervilhaca/milho); sistema IV (trigo/soja, aveia branca/soja, linho/soja e ervilhaca/milho, de 1987 a 1989, e trigo/soja, girassol ou aveia preta/soja, aveia branca/soja e ervilhaca/milho, de 1990 a 1995); sistema V (trigo/soja, trigo/soja, aveia preta ou aveia branca/soja e ervilhaca/milho); sistema VI (trigo/soja, trigo/soja, aveia branca/soja, linho/soja e ervilhaca/milho, de 1987 a 1989, e trigo/soja, trigo/soja, girassol ou aveia preta/soja. aveia branca/soja e ervilhaca/milho, de 1990 a 1995); e sistema VII (pousio de inverno/soja, a partir de 1990). Na média da receita por hectare líquida de 1987 a 1989, os sistemas IV e VI foram superiores aos sistemas 111 e V, respectivamente. Na média da receita líquida de 1990 a 1995, os sistemas avaliados não apresentaram diferenças significativas entre si.