Interactive effects of growth stage and nitrogen fertilization on herbage characteristics and nutritive value of Paspalum atratum

Abstract

AbstractPaspalum atratum is a tropical grass with potential to contribute to forage availability in areas dominated by waterlogged acidic soils. However, little is known of the interactive effect of N fertilization and stage of harvest on its nutritive value. Therefore, the objectives of this study were to evaluate the interactive effects of N fertilization and harvesting stage on herbage characteristics and nutritive value of P. atratum (Cv. Ubon) and to determine the optimum N fertilization rate at each stage of regrowth. P. atratum seedlings were planted in 18,631‐cm3 plastic pots containing growth media amended with 0, 25, 50, and 75 kg N/ha. Forage was harvested after 6‐ and 12‐weeks regrowth. Nitrogen fertilizer had a significant effect (p < 0.05) on herbage yield, sward height, crude protein yield, crude protein concentration, and 12‐ and 24‐h in vitro ruminal organic matter digestibility (IVOMD). P. atratum fertilized with 50 kg N/ha produced the highest dry matter yield (1,133 kg DM/ha) at 12‐week regrowth. Crude protein (CP) was highest (133 g/kg DM) in 6‐week regrowth forage that received 50 kg N/ha. IVOMD at 12 and 24 h of incubation was highest in 6‐week regrowth forage amended with 0 and 50 kg N/ha, respectively. Herbage characteristics and nutritive value of P. atratum showed a quadratic response to N fertilization at both regrowth stages. Response surface optimization indicated that N fertilizer application rates of 56.0 and 52.3 kg N/ha maximized P. atratum herbage yield, CP content, and 12‐h IVOMD at 6‐ and 12‐week regrowth, respectively. It was, therefore, concluded that the herbage yield and nutritive value of 6‐ and 12‐week regrowth P. atratum is optimized with N fertilizer rates of 56.0 and 52.3 kg N/ha, respectively.