AVALIAÇÃO DE GRAMÍNEAS FORRAGEIRAS SOB DOSES DE NITROGÊNIO EM SISTEMA DE INTEGRAÇÃO LAVOURA-PECUÁRIA.

Abstract

ABSTRAT: The objective of this study was to evaluate different strategies for the use of two forage grasses intercropped with maize in a crop-livestock integration system. The experiment was carried out in "Fazenda Barbosa", in the municipality of Brejo-MA, from February to September, 2017. The experimental design was the completely randomized in subdivided plots. In the plots were allocated the two grasses Urochloa brizantha cv. Marandu and Urochloa brizantha cv. Paiaguás intercropped with maize and in subplots the nitrogen doses (70, 100 and 130 kg ha-1 of N). The grasses were evaluated in 3 cycles: 1st cycle: marandu grass and paiaguás grass intercropped with maize in establishment with 150 days of growth; 2nd cycle: marandu grass and paiaguás grass 30 days after maize harvest and 3rd cycle: marandu grass and paiaguás grass 60 days after maize harvest. The variables studied were: height of pasture and extended tiller, tipping index, leaf dry mass, stem, dead forage, total forage, tiller density and leaf / stem ratio. In the 1st and 2nd cycles, the Paiaguás cultivar was superior to the Marandu cultivar for leaf dry matter, stem, total forage and population density of tillers and lower in the 2nd cycle in the leaf / stem ratio. In the second cycle, the paiaguás grass had a higher dry mass of leaves and total in the highest nitrogen doses (100 and 130 kg ha-1 of N), while the marandu grass was the lowest dose. In the 3rd cycle the cultivars were equal in total dry mass yield. In order to obtain a faster establishment of pasture after maize withdrawal, with higher productivity, it is recommended to cultivate Paiaguás fertilized with 100 kg ha -1 of nitrogen for the crop-livestock integration system. For the cultivar Marandu it is recommended to use 70 kg ha-1 of N. Silage experiment: The objective was to evaluate the chemical-bromatological characteristics of crop silages in a crop-livestock integration system. For the silage of the grasses, a completely randomized design was used in a 2x5 factorial arrangement (two grasses U. brizantha cv. Marandu and U. brizantha cv. Paiaguás) and five levels of sage hay inclusion (0, 4, 8,12 and 16 %) with five replications and the corn silage evaluation was adopted in a completely randomized design with three treatments (maize fertilized with 70, 100 and 130 kg ha-1 of N) with five replications. For the DM content of Paiaguás cultivar, a positive linear equation was fitted with the inclusion of Sabiá hay. A negative linear effect (P <0,05) was observed for the PB content with the addition of Sabiá hay to the Marandu grass. The value of NDF and FDA was adjusted to a positive linear equation for marandu grass and Paiguás grass, respectively, in the ensiled mass. The addition of Sabiá hay influenced (P <0,05) negatively the levels of hemicellulose, in the silage of paiaguás grass. It was observed a higher cellulose content (P <0,05) in the silage with paiguás grass. Lignin and ash contents were not influenced (P> 0,05) with the inclusion of hay in both silages. Corn silage fertilized with 70 kg ha-1 presented pH value of 3,81. For MS and PB contents, significant values were observed for corn silages fertilized with 100 kg ha-1. The NDF and ADF values of the silages fertilized with 70 kg ha-1 of N were higher than the others. The contents of hemicellulose and cellulose presented values similar to each other in all silages. There was no significant difference (P> 0,05) between treatments for lignin and ash contents. The inclusion of Sabiá hay in marandu grass and paiaguás grass silage is not recommended. It is recommended to use corn silage fertilized with 100 kg ha-1 of N.