Abstract Due to complementary resource use of the components, grass-clover mixtures are usually higher yielding compared to unfertilized pure grass stands. The number and identity of species in a mixture are known as important factors for the mixture’s productivity. How intraspecific variability of component species affects the productivity of mixtures has received less attention. We established an experiment to investigate how and to what extent different populations of white clover (Trifolium repens L.) affect mixture performance. Eight novel populations of white clover and one variety of perennial ryegrass (Lolium perenne L.) and chicory (Cichorium intybus L.) were grown as monocultures and in two- and three-species mixtures at two sites differing in soil fertility. Aboveground herbage was cut twice in the establishing year and four times in each of the three following years. The accumulated dry matter yield was calculated as the sum of the four annual dry matter yields. There was no significant interaction between white clover population and crop stand (i.e., white clover monoculture or mixtures with partner species) on dry matter yield accumulated over four years; the white clover population that performed well in monoculture also did so in mixtures. At both sites, the binary mixtures of white clover and chicory produced significantly higher dry matter yields than the white clover monocultures and other mixtures. Inclusion of chicory in mixtures significantly increased the stability of yield production as well. Site conditions strongly affected the performance of the forage species mixtures. We found that the benefit of mixtures over monocultures was more related to the identity of species in mixture than to the white clover population.

中文翻译：

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白三叶草种群对多年生黑麦草和菊苣混合物生产力和产量稳定性的影响

摘要 由于成分的互补资源利用，与未施肥的纯草丛相比，草-三叶草混合物通常具有更高的产量。混合物中物种的数量和特性被认为是混合物生产力的重要因素。组分物种的种内变异如何影响混合物的生产力受到的关注较少。我们建立了一个实验来研究不同种群的白三叶草 (Trifolium repens L.) 如何以及在多大程度上影响混合物性能。八个新的白三叶草种群和一种多年生黑麦草 (Lolium perenne L.) 和菊苣 (Cichorium intybus L.) 在土壤肥力不同的两个地点作为单一栽培和两种和三种混合物种植。地上牧草在建立年份砍伐两次，随后三年每年砍伐四次。累积干物质产量计算为四个年度干物质产量的总和。白三叶草种群和作物林分（即白三叶草单一栽培或与伙伴物种混合）对四年累积的干物质产量没有显着的相互作用；在单一栽培中表现良好的白三叶草种群在混合栽培中也表现良好。在这两个地点，白三叶草和菊苣的二元混合物产生的干物质产量明显高于白三叶草单一栽培和其他混合物。在混合物中加入菊苣也显着提高了产量的稳定性。场地条件强烈影响草料物种混合物的性能。