Parthenium hysterophorus is a prolific invasive weed species, which infests many crops in over 40 countries around the world. A 2-year field study was carried out to quantify the potential impacts of this weed on direct-seeded rice. Parthenium weed was allowed to compete for 2, 4, 6 or 8 weeks after crop emergence, while full season weedy and weed-free plots were maintained as controls. Parthenium weed plants grew taller and attained more biomass as the competition duration prolonged. The yield and yield-related attributes of rice were negatively affected with increasing competition duration. The season-long competition caused the highest reductions in panicle number (28–34%), panicle length (26–27%), grains per panicle (22–23%) and grain yield (33 and 38%) of rice in both years. Weed competition for 2–8 weeks caused 5–34% and 6–33% losses in rice grain yield during both years, respectively. Importantly, Parthenium weed control after 8 weeks of competition did not improve rice yield significantly. The results suggested that Parthenium weed should be controlled in rice fields between 4 and 8 weeks after crop emergence under direct-seeded conditions to avoid over 10% yield losses.

中文翻译：

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Parthenium hysterophorus在直播好氧稻田中的竞争动态

Parthenium hysterophorus是一种多产的入侵杂草物种，在全球 40 多个国家/地区侵染许多作物。进行了一项为期 2 年的实地研究，以量化这种杂草对直播水稻的潜在影响。在作物出苗后允许部分杂草竞争 2、4、6 或 8 周，而保持全季杂草和无杂草的地块作为对照。随着竞争持续时间的延长，Parthenium 杂草植物长得更高，获得更多的生物量。随着竞争持续时间的增加，水稻的产量和产量相关属性受到负面影响。为期一季的竞争导致水稻的穗数（28-34%）、穗长（26-27%）、每穗粒数（22-23%）和产量（33%和38%）下降幅度最大。年。2-8 周的杂草竞争导致这两年稻谷产量分别下降 5-34% 和 6-33%。重要的是，经过 8 周的竞争控制 Parthenium 杂草并没有显着提高水稻产量。结果表明，稻田应在直播条件下在作物出苗后 4 至 8 周内控制 Parthenium 杂草，以避免超过 10% 的产量损失。