Effects of Conventional or Slow-release Urea on Productivity, Tillering, Water use Efficiency and Chemical Composition of Tropical Grasses

Nitrogen (N) is an essential nutrient for growth and plant physiology; but a lot of the N is lost during metabolization, especially by N volatilization. This study aimed to evaluate the effects of slow-release urea fertilizer on productivity, nutritive value, and morphological characteristics of Urochloa gender grasses. The study was designed as a randomized complete block in a factorial scheme (4 × 3) with five repetitions where four grasses and three treatments were used. The grasses were: Urochloa brizantha cv. Braúna (BR), Urochloa brizantha cv. BRS Paiaguás (PA), Urochloa decumbens cv. Basilisk (BA) and Urochloa hybrid cv. Camello (CA) and the treatments were: i) no fertilizing [control (CTRL)]; ii) conventional fertilizer (CF) applied to achieve 128 kg/ha of N from conventional urea, and iii) slow-release urea (SF) [128 kg/ha of N from urea coated by 1-3% of H2SO4]. Forage accumulation rate was greater by 27.6% in the CF and SF treatments compared to CTRL (P < 0.01). Leaf production (DM basis) was greater for CA and PA on CF and SF treatments but were similar in CTRL treatment (P = 0.01). An interaction for dry matter content between grass and fertilizer treatment was observed (P < 0.01). The U. brizantha cv. Braúna had greater forage production and tiller population density. The BRS Paiaguás had a greater proportion of green leaves and dry leaf mass. Slow-release urea did not increase the forage yield, but the leaf yield was greater in U. decumbens cv. Basilisk. Additionally, slow-release urea increased the water-use efficiency in U. decumbens cv. Basilisk and U. brizantha cv. Braúna