Forage yield of Coastcross-1 pastures inoculated with Azospirillum brasilense

ABSTRACT. The high cost of nitrogen fertilizers increases the expenses in pasture-based animal production. The inoculation with plant growth-promoting bacteria is an alternative to reduce the costs. This study evaluated the forage yield of Coastcross-1 pastures inoculated with Azospirillum brasilense, fertilized with different levels of nitrogen and subjected to cuts. The experiment was a factorial randomized block design with three replications. The factors were the inoculation (without inoculation, inoculated only at planting and reinoculated in the second year), levels of nitrogen (0, 100 and 200 kg ha-1 year-1 N) and seasons (spring, summer, fall and winter) when cuts were made. Forage yield, forage accumulation rate, botanical and structural pasture composition were evaluated. Forage yield without nitrogen fertilizer in pastures was in the first year 9.1, 11.7 and 11.7 t ha-1 DM, and in the second year 8.6, 11.2 and 11.5 t ha-1 DM, for the factor inoculation, respectively. The forage yield rises with inoculation at pasture planting, without nitrogen fertilization. Reinoculation is not necessary.摘要 氮肥成本高昂，推高了以牧草为基础的畜牧生产成本。接种植物促生菌（plant growth-promoting bacteria）是降低此类成本的可行途径。本研究针对接种巴西固氮螺菌（Azospirillum brasilense）、施加不同水平氮肥并经刈割处理的岸杂1号（Coastcross-1）牧草地，对其牧草产量展开评估。本试验采用因子随机区组设计，设置三次生物学重复。试验因子涵盖接种处理（不接种、仅定植时接种、第二年复接种）、氮肥施用量（0、100、200 kg·hm⁻²·a⁻¹ 纯氮）以及刈割季（春季、夏季、秋季、冬季）。测定指标包括牧草产量、牧草累积速率、牧草地植物群落组成及结构组成。在不施加氮肥的牧草地中，不同接种处理组的牧草干物质（dry matter，DM）产量第一年分别为9.1、11.7和11.7 t·hm⁻²，第二年分别为8.6、11.2和11.5 t·hm⁻²。在不施加氮肥的条件下，定植时接种可提升牧草产量，且无需进行复接种。