Nitrogênio e enxofre acumulado no capim-marandu

Abstract

Nitrogen (N) is of great importance for the formation and development of forage grasses, and its effect has been shown to be dependent on sulfur (S) supply due to the interaction of these nutrients during plant metabolism. The objective of this work was to study the influence of N and S dose combinations on the nutritional characteristics of the marandu grass, such as the N and S accumulated in the aerial part and roots, and to evaluate the dry mass of shoot and roots. The experiment was carried out in a greenhouse, in Barra do Garças, MT, from November 2017 to January 2018. Five doses of N (0, 100, 200, 300 and 400 mg dm-3 ) were used and five doses of S (0, 10, 20, 30 and 40 mg dm-3 ), combined on a response surface based on an experimental design with a fractionated factorial. Two plant cuts were performed at interval of 30 days. After each cut the shoot was separated in FE - leaf expansion, LR - leaf newly expanded, LM - adult leaf blade and CB + sheath, and after the second cut the root was washed. Each part was placed in a greenhouse and dried to a constant weight to obtain the mass of the dry matter, after which it was ground in a Willey type mill for quantification of N and S. For the mass of dry matter, the interaction between the doses of N and S was significant in the first and second cuts of the grass, in the mass of total dry matter and in the FE, LR, LM and CB of the second cut. There was an isolated effect of N on the LR, LM and CB of the first cut. The interaction between the N and S doses was significant for N accumulated only in the second in FE, LR, LM and roots, with isolated effect of N in both cuts in CB and in the first cut in FE, LR and LM. The accumulated S had interaction between the doses in the two cuts in the LR and LM and in the second cut in the FE and CB. The best observed N: S ratio for most N variables was 20: 1 and for most S variables it was 12: 1. The isolated effect of N doses is more significant than S isolated effect of S, not occurring isolated effect of S.