Seed shatter is an important weediness trait on which the efficacy of harvest weed seed control (HWSC) depends. The level of seed shatter in a species is likely influenced by agroecological and environmental factors. In 2016 and 2017, we assessed seed shatter of eight economically important grass weed species in soybean [Glycine max (L.) Merr.] from crop physiological maturity to 4 wk after maturity at multiple sites spread across 11 states in the southern, northern, and mid-Atlantic United States. From soybean maturity to 4 wk after maturity, cumulative percent seed shatter was lowest in the southern U.S. regions and increased moving north through the states. At soybean maturity, the percent of seed shatter ranged from 1% to 70%. That range had shifted to 5% to 100% (mean: 42%) by 25 d after soybean maturity. There were considerable differences in seed-shatter onset and rate of progression between sites and years in some species that could impact their susceptibility to HWSC. Our results suggest that many summer annual grass species are likely not ideal candidates for HWSC, although HWSC could substantially reduce their seed output during certain years.

中文翻译：

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美国多个地区经济重要杂草在大豆收获时的落粒物候。第 2 部分：草种

落粒是一种重要的杂草性状，收获杂草种子控制 (HWSC) 的功效取决于它。一个物种的种子破碎程度可能受农业生态和环境因素的影响。在 2016 年和 2017 年，我们评估了大豆中 8 种经济重要禾本科杂草的种子破碎度[最大甘氨酸(L.) Merr.] 从作物生理成熟到成熟后 4 周，分布在美国南部、北部和大西洋中部的 11 个州的多个地点。从大豆成熟到成熟后 4 周，美国南部地区的累积种子破碎百分比最低，并且向北穿过各州增加。在大豆成熟时，种子破碎的百分比在 1% 到 70% 之间。到大豆成熟后 25 天，该范围已转变为 5% 至 100%（平均：42%）。在一些物种中，不同地点和年份的种子破碎发生和进展速度存在相当大的差异，这可能会影响它们对 HWSC 的易感性。我们的研究结果表明，许多夏季一年生草种可能不是 HWSC 的理想候选者，尽管 HWSC 在某些年份可能会大大减少其种子产量。