Abstract

Due to the change in the environment, diseases and insects can reduce the leaf area of agricultural crops. The objective of this study was to determine the impact of induced defoliation on the vegetative and reproductive phases of corn on its agronomic characteristics. The experiment was carried out in the experimental area of the Mato Grosso Federal Institute of Education, Science and Technology, Campo Novo do Parecis campus, in a second crop system in the 2017/2018 agricultural year, with sowing in March. This study used a randomized complete block design, consisting of 24 treatments and three replications, comprising eight phenological stages. The treatments were performed from the fourth leaf stage (V4) to physiological maturation (R5), with defoliation in the lower, middle and upper thirds of the plant. The characteristics evaluated were: plant height, stem diameter, ears insertion height, ears length, ears diameter, ears weight, number of rows per ears, number of grains per row, weight of grain per ears, prolificity; harvest index, weight of one thousand grains and grain yield. Defoliation between the fourth (V4) and twelfth leaves (V12) does not interfere in the evaluated characteristics. Grain and ear weight are interfered when defoliation occurs in the middle and upper third of plants in V12. Defoliation between flowering (R1) and beginning of grain filling (R2) negatively affects the weight of one thousand grains, grain and ear weight, and may reduce grain yield by up to 30%. Defoliation in the upper third of the plant significantly reduces the diameter and length of ears, grain and corn ear of the corn crop.

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