Effects of nitrogen fertilization on protein and carbohydrate fractions of Marandu palisadegrass
Rhaony Gonçalves Leite, Abmael da Silva Cardoso, Natália Vilas Boas Fonseca, Maria Luísa Curvelo Silva, Luís O Tedeschi, Lutti Maneck Delevatti, Ana Cláudia Ruggieri, Ricardo Andrade Reis
Abstract
Abstract The effects of nitrogen (N) fertilization levels on protein and carbohydrate fractions in Marandu palisadegrass pasture [ Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster] were investigated in a pasture over five years. The experimental design was completely randomized with four levels of N (0, 90, 180, and 270 kg N ha -1 , as urea) for five years, and with three replicates. The study was conducted in a continuously stocked pasture during the forage growing season (December to April) in a tropical region. The effects of N fertilization were similar across the five years. With increasing N fertilization, the concentrations of crude protein (CP) increased from 103 to 173 g kg −1 ( P < 0.001), soluble fractions (Fraction A + B1) increased from 363 to 434 g kg −1 of total CP ( P = 0.006); neutral detergent fiber (NDF) decreased from 609 to 556 g kg −1 ( P = 0.037); indigestible NDF ( P = 0.046), potentially degradable neutral detergent fiber ( P = 0.037), and acid detergent fiber decreased ( P = 0.05), and total digestible nutrient (TDN) increased ( P < 0.001). Increasing N fertilization decreased the concentrations of Fraction C ( P = 0.014) and total carbohydrates ( P < 0.0001), and increased CP:organic matter digestibility ( P < 0.01). Concentrations of neutral detergent fiber free of ash and protein (P = 0.003), indigestible neutral detergent fiber ( P < 0.001), neutral detergent fiber potentially degradable ( P = 0.11), CP ( P < 0.001), Fraction A + B1 ( P < 0.001), Fraction B2 ( P < 0.001), Fraction B3 ( P < 0.01), and non-structural carbohydrates differed ( P < 0.001) across years. Therefore, N fertilization can be used to increase CP, soluble protein, and TDN.