Defoliation at different vegetative stages and assessment of morphological and yield components

Abstract

Our objective was to evaluate the influence of defoliation at different vegetative stages on morphological characters and yield components of an indeterminate soybean cultivar. The study was conducted in 2010/11 and 2011/12. The experimental design was a randomized block design with seven treatments and four replications for each year. The treatments were: T1: No defoliation; T2: Defoliation in V4, T3: Defoliation in V4 and V5, T4: Defoliation in V4, V5 and V6, T5: Defoliation in V4, V5, V6 and V7, T6: Defoliation in V4, V5, V6, V7 and V8 and T7: Defoliation in V4, V5, V6, V7, V8 and V9. Defoliation was simulated artificially, in specified periods where we proceeded to remove all leaves from each node including the petiole. The variables analyzed were: main stem height, number and length of branches, first pod, number of pods per node on the main stem, and the branches per plant, number of reproductive nodes on the main stem, the branches, number of us total on the main stem, the branches, distance between us and grain yield. Grazing did not influence most of the morphological characters and increments the number of pods on the stem in years with good water availability and high levels of defoliation, and of soybean yield.

Morphological and Grain Yield Responses of Soybean (Glycine Max L.) to Time and Intensity of Defoliation Under Application of Amino Acid

“…It is also known that defoliation intensity may vary along nutrient availability gradients and that defoliation may alter competition relationship between species (Alhamd and Alrababah, 2008). The ability of soybean to prevent substantial reduction in yield after the loss of leaves caused by defoliators and disease depends on several factors among including intensity of, the phenological stage of development at the time of defoliation, duration of defoliation, the ability of cultivar to tolerate or compensate for defoliation, and environmental conditions, especially rainfall, temperature and solar radiation (Nardino et al, 2016). Regarding the percentage of defoliation, research has established levels for the control of insect pests, when the defoliation is greater than 30% in the vegetative phase, or 15% in the reproductive phase.…”

“…However, these recommendations are based on work done in the 70-80's decades. In this sense, another key issue for reduction of income is the degree to which defoliation reduces light interception by the canopy (Nardino et al, 2016). Earlier studies addressed the effect of leaf removal on growth and yield.…”