Abstract

Nitrogen fertilization is widely recognized as a key factor influencing tropical grass productivity; however, its effectiveness may vary according to pasture developmental stage and management practices. This study evaluated the effects of five nitrogen rates (0, 75, 150, 225, and 300 kg ha−1) and two post-cutting residual heights (20 and 30 cm) on the productive, morphological, and nutritional characteristics of Aruana grass (Megathyrsus maximus cv. Aruana) under irrigated conditions. Treatments were arranged in a randomized complete block design with a split-plot structure. Nitrogen was applied as urea in three split applications following simulated grazing events. Herbage mass, dry matter yield, morphological composition, chemical composition, and in vitro dry matter digestibility were evaluated. No interaction was detected between nitrogen fertilization and residual height. Nitrogen fertilization did not affect forage production, morphological composition, chemical composition, or digestibility under the conditions of this study. Residual height influenced forage accumulation, with greater herbage mass and dry matter yield observed at 20 cm than at 30 cm (p = 0.006), without affecting forage quality. These preliminary findings indicate that residual height may be an important factor affecting forage accumulation in irrigated Aruana grass during pasture establishment. Additional studies conducted over multiple growing seasons and environmental conditions are required before definitive management recommendations can be made.

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