Effect of defoliation levels on recovery of leaf area, on yield and agronomic traits of soybeans

Abstract

Four levels of defoliation (0, 33, 67 and 100%) were applied at four stages of development (V₃, V₈, R₂ and R₆) of soybeans (Glycine max (L.) Merrill) cv. Paraná, at the Embrapa-Centro Nacional de Pesquisa de Soja experimental station in Londrina, PR, Brazil. Plants were defoliated by hand, cutting off one leaflet of each leaf for each 33% of defoliation. Recovery of leaf area was measured at five and twelve days after defoliation, and mathematical simulations were made to study parameters of recovery. Results indicated intense recovery measured by liquid daily rate of leaf area increase (dr) and recovery time (rt) for low defoliation levels, specially when applied at vegetative stages. During the reproductive period, levels of defoliation reduced the rate of the soybean natural trend of losing leaf area. Yield was affected only by 67 and 100% defoliation applied at R₆, while main agronomic traits such as date of harvesting maturity, plant lodging and height were not affected by the treatments.