Morphogenic, structural, productive and bromatological characteristics of Braquiária in silvopastoral system under nitrogen doses

ABSTRACT. This study aimed to evaluate the effect of different doses of nitrogen fertilization on the morphogenic, structural, productive and chemical composition of Urochloa decumbens (Stapf) R. D. Webster cv. Basilisk in a silvopastoral system with eucalyptus. The experimental treatments consisted of pastures of Basilisk cultivar, fertilized with 0, 100, 200, 300 and 400 kg ha-1 year-1 of N, and intercropped with eucalyptus, clone GG 100 (Eucalyptus grandis x E. urophylla). The experimental arrangement followed a randomized block design with four replicates. The evaluated characteristics were: foliar appearance rate, phyllochron, leaf length, leaf elongation rate, leaf life span, foliar senescence rate, number of green leaves per tiller, number of senescent leaves per tiller, daily dry matter accumulation, dry matter production, crude protein, and neutral detergent fiber. In the conditions of the established silvopastoral system, nitrogen fertilization did not influence (p > 0.05) the morphogenic and structural characteristics of Basilisk cultivar, except for height (p < 0.01) and leaf: stem ratio (p = 0.02). The nitrogen fertilization of the Brachiaria grass with eucalyptus in the proposed structural arrangement does not modify (p > 0.05) the morphogenic characteristics. However, in ration to dry matter production, doses of up to 400 kg of N ha-1 are recommended.

摘要。本研究旨在评估不同施氮水平对设置尾巨桉（Eucalyptus grandis × E. urophylla）无性系GG 100间作的林牧复合系统中，‘Basilisk’品种俯仰臂形草（Urochloa decumbens (Stapf) R. D. Webster）的形态发生、结构、生产及化学成分的影响。试验处理为：与尾巨桉无性系GG 100间作的‘Basilisk’品种臂形草牧场，分别施用0、100、200、300、400 kg·ha⁻¹·a⁻¹的氮肥。试验采用随机区组设计，设置4次重复。测定指标包括：叶片出现速率、叶间期、叶长、叶片伸长速率、叶片寿命、叶片衰老速率、每分蘖绿叶数、每分蘖衰老叶数、日干物质积累量、干物质产量、粗蛋白以及中性洗涤纤维（neutral detergent fiber）。在本林牧复合系统的试验条件下，氮肥施用对‘Basilisk’品种臂形草的形态发生与结构性状均无显著影响（p>0.05），仅株高（p<0.01）和叶茎比（p=0.02）除外。本试验采用的林牧复合结构中，对臂形草施加氮肥不会显著改变其形态发生性状（p>0.05）。但就干物质产量而言，推荐施用最高400 kg·ha⁻¹的氮肥。