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剂量对桉树间作林牧复合系统（silvopastoral system）中俯仰臂形草（Urochloa decumbens (Stapf) R. D. Webster）品种‘巴兹利克’（Basilisk）的形态发生、结构、生产性状及化学成分的影响。实验处理设置为：巴兹利克品种牧草地施氮量分别为0、100、200、300和400 kg·ha⁻¹·a⁻¹，并与无性系GG 100（巨桉×尾叶桉，Eucalyptus grandis × E. urophylla）桉树进行间作。实验采用随机区组设计，设置4次重复。本次评估的性状包括：叶片出现速率、出叶间隔期（phyllochron）、叶片长度、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（crude protein）及中性洗涤纤维（neutral detergent fiber）。在所建立的林牧复合系统条件下，氮肥施用对巴兹利克品种的形态发生与结构性状无显著影响（p>0.05），仅株高（p<0.01）与叶茎比（p=0.02）受其显著调控。在本研究设定的间作结构下，为该臂形草施加氮肥并不会对其形态发生性状产生显著改变（p>0.05）。但就干物质产量而言，推荐施氮量最高可达400 kg·ha⁻¹·a⁻¹。