CROP-ROTATION IN GUARAPUAVA, PR BRAZIL .1 6. ENERGETIC EFFICIENCY OF ROTATION SYSTEMS FOR WHEAT, UNDER NO-TILLAGE

From 1984 to 1989, at the Cooperativa Agraria Mista Entre Rios Ltda., in Guarapuava, PR, Brazil, plant species composing rotation systems fo r wheat on energetic efficiency were assessed. Four rotation systems f or wheat were studied: 1) monoculture; 2) one winter without wheat; 3) two winters without wheat; 4) three winters without wheat. Both winte r (white oat, barley, common vetch, flax, wheat, and lupin) and summer (corn and soybean) crops were seeded under no-tillage. The energetic efficiency is calculated by dividing the grain yield of each crop by c ropping energy, represented by the commodities and labor employed in t he cropping systems. Energetic efficiency of crops studied was affecte d by the period. White oat, barley, and wheat crops showed higher ener getic efficiency compared to other winter crops. The best energetic ef ficiency was obtained by corn.