Implications of grass–clover interactions in dairy pastures for forage indexing systems. 3. Manawatu

The implementation and monitoring of the treatments in the core experiment (eight perennial ryegrass cultivars grown under four combinations of plus/minus clover and high/low nitrogen (N)) at a dryland Manawatu site are described. Herbage accumulation (HA) was significantly greater for high N than for low N in 14 out of 21 annual and seasonal totals. There were no significant main effects of clover and there were no interactions between clover and N level. With the exception of autumn 2016, there were significant differences among ryegrass cultivars in all seasons, but no clover × cultivar or N × cultivar interactions for HA or nutritive value (NV). With the caveat that successive droughts reduced the proportion of white clover to low levels, the hypothesis that relative HA or NV rankings of ryegrass cultivars do not differ when ryegrass is grown in monoculture or in mixtures with white clover is supported.

本研究详述了位于马纳瓦图（Manawatu）旱地试验点的核心实验处理方案的实施与监测流程：实验选用8个多年生黑麦草（perennial ryegrass）品种，设置4种三叶草（clover）有无与高/低氮（N）水平的组合处理。在21组年度及季节总计数据中，有14组显示高氮处理下的牧草累积量（Herbage Accumulation, HA）显著高于低氮处理。三叶草处理无显著主效应，且三叶草与氮水平间未出现显著交互作用。除2016年秋季外，所有季节的多年生黑麦草品种间均存在显著差异，但牧草累积量与营养价值（Nutritive Value, NV）均未表现出三叶草×品种或氮×品种的交互效应。需注意的是，连续干旱导致白三叶草（white clover）占比降至极低水平，在此前提下，“多年生黑麦草单作或与白三叶草混播时，其相对牧草累积量与营养价值排名无差异”这一假说得到了验证。