Altura de manejo do capim mombaça em sistema silvipastoril sob duas distâncias do renque de árvores

Abstract

The objective was to evaluate productive, morphostructural, growth characteristics and chemical - bromatological composition of the forage Mombaça, submitted to different cutting heights in a conventional (full sun) and silvopastoral system, in two positions in relation to the row of trees (top of the trees trees and halfway between the lines). The experiment was conducted at the Federal Institute of Education, Science and Technology, located in the city of Colinas do Tocantins, in a tropical environment, characterized by a typical Ortic Quartzarênico Neosol, average annual precipitation of 1800 mm, average annual temperature of 26 ºC, being evaluated between the months of December and April of the years 2019 and 2020. A completely randomized design was used, with repeated measures over time, in a 3 x 4 factorial scheme, with three environments: full sun or monoculture, treetops and middle of the rows, represented by the silvopastoral system, respectively at 1 and 6 meters from the eucalyptus line, and four plant heights at the moment of cutting (50, 70, 90 and 110 cm), with four repetitions each, totaling 48 experimental units. The environments and the different cutting heights of the plants, as well as the interaction of both, influenced the productive, morphostructural and growth characteristics of Mombaça grass. The threshold between 70 and 90 cm was where the best proportions of leaves in relation to stem and dead material occurred in the conventional system. In silvopastoral, the height that provided forage with the best structure was 70 cm. Above 80 cm there is a linear drop in tillering, forage density and photosynthetic efficiency in the three environments. The chemical bromatological composition of mombaça grass was influenced by the collection sites for the variables: mineral matter content, phosphorus content and magnesium content, caused by the concentration of these nutrients due to a lower production. The different cutting heights influenced: crude protein, phosphorus and potassium content, which showed decreasing linear effects; neutral detergent fiber, acid detergent fiber and magnesium contents that showed increasing linear effects. The forages produced under the influence of the tree canopy showed a greater increase in minerals in their chemical-bromatological composition, however these values were mainly caused by the concentration of elements, given lower mass production in the shaded environment.