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.
Highlights
Corn (Zea mays L.) is an important commodity in global nutrition and its yield is dependent on the how a plant allocates the accumulated biomass between the corn grains and other plant parts
At V5, the apical meristem develops below ground, which explains that at that stage, the plant can undergo some injury on the aerial part and recover with no significant damage to its production performance, since the number of grain rows per ears is defined at V8, while the number of grains per row until the V17 stage (Ritchie et al, 1993; Magalhães & Durães, 2006; Alvim et al, 2010)
The real impact on yield caused by stress, whether water or caused by leaf area removal, affects the period from pre-flowering (VT) to grain filling (R2), according to the phenological scale of Ritchie et al (1993) and Brito et al (2011)
Summary
Corn (Zea mays L.) is an important commodity in global nutrition and its yield is dependent on the how a plant allocates the accumulated biomass between the corn grains and other plant parts. At V5, the apical meristem develops below ground, which explains that at that stage, the plant can undergo some injury on the aerial part and recover with no significant damage to its production performance, since the number of grain rows per ears is defined at V8 (eighth developed leaf), while the number of grains per row until the V17 stage (Ritchie et al, 1993; Magalhães & Durães, 2006; Alvim et al, 2010). The production would be reduced, because corn is the species of agricultural importance that most expresses its productive potential due to the use of solar radiation (Strieder et al, 2007)
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