EFFECT OF DEFOLIATION LEVELS ON RECOVERY OF LEAF-AREA, ON YIELD AND AGRONOMIC TRAITS OF SOYBEANS

Four levels of defoliation (0, 33, 67 and 100%) were applied at four s tages of development (V-3, V-8, R-2 and R-6) of soybeans (Glycine max (L.) Merrill) cv. Parana at the Embrapa-Centro Nacional de Pesquisa de Soja experimental station in Londrina, PR, Brazil. Plants were defoli ated by hand, cutting off one leaflet of each leaf for each 33% of def oliation. Recovery of leaf area was measured at five and twelve days a fter defoliation, and mathematical simulations were made to study para meters of recovery. Results indicated intense recovery measured by liq uid daily rate of leaf area increase (dr) and recovery time (rt) for l ow defoliation levels, specially when applied at vegetative stages. Du ring the reproductive period, levels of defoliation reduced the rate o f the soybean natural trend of losing leaf area. Yield was affected on ly by 67 and 100% defoliation applied at R-6, while main agronomic tra its such as date of harvesting maturity, plant lodging and height were not affected by the treatments.