Perdas quali-quantitativas de algodão : influência do atraso na colheita

Abstract

Harvest is one of the most important processes within the cotton production chain, insofar as, it is the most exposure period of the fiber to climate issues, dust and deposition of particles of leaves and other materials, which can reduce fiber quality and favor the loss of cotton fibers if the harvest it is performed late. Thus, the objective of this study was to evaluate the pre-harvest losses and the qualitative variation of the fiber of two cotton cultivars due to the delay harvest, and according to the position of the bud in the plant. The experiment was conducted in the 2016/17 harvest, in the production area of the Caregi Farm, located in the municipality of Ipiranga do Norte - MT. Two cultivars (FM 944 GL and TMG 81 WS) grown in fields side by side were evaluated. Before the samples were collected, a defoliation herbicide and a growth regulator were applied. Pre-harvest losses were measured in three stages, the first one being considered ideal for harvesting, followed by two subsequent harvesting stages, setting in arrears. A manual collection of the cotton boll found in the soil was carried out and arranged within a collection area marked in each plot, in three replications at each stage. The fiber quality was determined according to the insertion of the boll in the plant: upper, middle and lower part. The analyzes of fiber characteristics were carried out in the Fiber Classification Laboratory of COOAMI (Industrial and Commercial Cooperative of the producers of Sorriso) using the HVI (High Volume Instrument). There were significant losses of cotton in the soil in relation to the harvest delay for both cultivars. TMG 81 WS presented higher losses over time with an overall mean of 3.79 ha-1 and the mean FM 944GL loss was 2.85 ha-1. The delay in the harvest favored the increase of particles present in the fiber and reduced the resistance, elongation and micronaire index. The cultivar FM 944 GL showed better performance about the fiber yield, micronaire index, length, degree of reflectance and degree of color, besides presenting lower leaf grade, quantity and area of impurities. In relation to the position in the plant, cotton of higher quality was verified in the upper part of the plant.