Forage plants are the most important food source for ruminants. The nutritive value and digestibility of forage grass depends on N supply. This study aimed to evaluate the effects of N fertilization, rates and nitrogen sources on chemical composition, in vitro digestibility, in Aruana Guinea grass (Panicum maximum Jacq.) cultivated in good soil fertility, under greenhouse conditions. The experiment was performed at the Institute of Animal Science, at the municipality of Nova Odessa, Sao Paulo State (Brazil), from April to June (Fall season) using a randomized blocks experimental design with four replication, in a factorial scheme 4 x 2 (rates and nitrogen sources). The grass was grown in clay Oxisol red in which were applied 0; 150; 300 and 450 N kg/ha and two sources of urea (urea untreated and coated urea with the urease inhibitor N-(n-butyl) thiophosphate triamide - NBPT).Two harvests were performed and each of them the grass was harvested about 30 days of growth, the vegetal material was separated into: a) blade leaf and b) stems. The nitrogen application significantly (P< 0.01) increased the dry matter accumulation and crude protein (CP) on leaves and stems in both cuts. Nitrogen fertilization increased linearly IVDMD and decreased NDF and ADF. Moreover, there was improved in the values of cell wall constituents and therefore the forage quality. The use of UR + urease inhibitor (NBPT) in regrowth with interval of 28 days resulted in higher CP contents and forage digestibility. Forage quality was improved with N rates greather than 150 kg/ ha.

Fonte: International Journal of Agriculture Innovations and Research, v.4, n.3, 2015.