CROP-ROTATION IN GUARAPUAVA .17. ENERGETI C EFFICIENCY OF ROTATION SYSTEMS FOR BARLEY CROP, UNDER NO-TILLAGE

In the period from 1984 to 1989, at the Cooperative Agraria Mista Entr e Rios Ltda., in Guarapuava, PR, Brazil, the effects of rotation syste ms for barley on energetic efficiency were assessed. Four rotation sys tems for barley were studied: 1) monoculture; 2) one winter without ba rley; 3) two winters without barley; 4) three winters without barley. Both winter (white oat, barley, common vetch, and flax) and summer (co rn and soybean) crops were seeded under no--tillage. The energetic eff iciency is the ratio of grain yield of each crop by the cropping energ y, represented by the commodities and labor executed in the cropping s ystems. Energetic efficiency of crops studied was influenced by the cr opping period. White oat and barley crops showed higher energetic effi ciency than the other winters crops. The best energetic efficiency was obtained for corn.