Pasture legumes that persist under challenging agroecological conditions are crucial to ensure high lamb growth rates in dryland pastures. Pasture and lamb production from binary and diverse mixtures (Mix) of tall fescue (TF) with white clover (Whc), balansa clover (Bc), subterranean clover (Sc) and birdsfoot trefoil (Bft) were compared in a summer‐dry hill site in Corvallis, Oregon over a two‐year period. In 2018, all pasture combinations provided similar lamb liveweight gains (LWG, mean 177 g/day) in the first half of spring. Lambs in TF‐Bc and TF‐Mix pastures grew 31 to 41 g/day faster than those grazing TF‐Sc, TF‐Whc and TF‐Bft in the second half of spring (p < .05). Overall, TF‐Bc and TF‐Mix had higher (p < .05) legume contents (32% and 37% respectively) compared to other pasture combinations. In spring 2019, lambs that grazed the TF‐Mix and TF‐Whc pastures had higher LWG than those on other pastures (p < .05). The superior lamb growth rates were associated with the higher legume content and pasture quality maintained into the late spring period. Overall, the legume content of all pastures decreased over the course of the two‐year trial, with the decline being substantial for balansa clover. The present study confirmed that a high legume content of pastures leads to greater lamb growth rates. Total annual yields of pastures that had greater legume contents were superior to others (p < .05). Thus, a combination of self‐regenerating annual clovers with perennial legumes in pasture mixtures may ensure a higher legume content and longer persistence in dryland hill pastures.

中文翻译：

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夏季干旱丘陵草场的牧草生产，豆类的持久性和羔羊生长

在具有挑战性的农业生态条件下持续存在的牧草豆类对于确保旱地牧草的高羊羔生长率至关重要。在夏干的山丘上比较了高羊茅（TF）与白三叶草（Whc），巴兰萨三叶草（Bc），地下三叶草（Sc）和鸟足三叶草（Bft）的二元和多种混合物（Mix）的牧草和羊肉产量两年内在俄勒冈州科瓦利斯的工厂。在2018年的春季上半年，所有牧场组合都增加了类似的羔羊活重（LWG，平均177克/天）。TF-Bc和TF-Mix牧场的羔羊的生长速度比春季下半年TF-Sc，TF-Whc和TF-Bft的羔羊快31至41 g /天（p  <.05）。总体而言，TF-Bc和TF-Mix具有更高的（p <.05）与其他牧场组合相比，豆科植物的含量（分别为32％和37％）。在2019年春季，放牧TF-Mix和TF-Whc牧场的羔羊的LWG高于其他牧场的绵羊（p  <.05）。较高的羔羊生长速度与较高的豆类含量和到春末时期保持的牧场质量有关。总体而言，在两年的试验过程中，所有草场的豆类含量均下降，而三叶草的下降幅度很大。本研究证实，高豆科牧草含量导致较高的羔羊生长率。豆类含量较高的牧草的年总产量优于其他牧草（p <.05）。因此，将自生的一年生三叶草与多年生豆科植物混合在牧草混合物中，可以确保较高的豆科植物含量和在旱地丘陵草场中的持久性。