Early infestation of weeds in onion crop is one of the major constraints limiting the establishment of the crop and thereafter its production. An yield reduction of 48-85 percent was reported in weed infested field (Patel et al., 1983; Mandal, 1997). The conventional method of weed control through hand weeding is costly and non-availability of labour at the critical stages results in severe loss in yield. This situation makes it necessary to use herbicides for effective and timely control of weedsin onion. In addition, maintenance of adequate plant population is an important factor for getting higher yield which also influences weed density in the field. Row spacing has significant effect on weed dry matter and it is positively correlated with weed population (Shah and Patel, 1995). Spacing of plants tends to modify the microclimate which in turn influences metabolic activities of plants and consequently their growth and development. Keeping in view the importance of maintenance of adequate plant population and the problems faced by the farmers due to labour shortage at critical stages of growth, an investigation was undertaken to evaluate the efficiency and economics of chemical weedicides under varying planting densities for weed control andproductivity of onion.
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机译：洋葱作物中杂草的早期侵染是限制作物建立以及随后生产的主要限制之一。据报道，在杂草侵染的田地里，单产降低了48％至85％（Patel等，1983; Mandal，1997）。通过手工除草来控制杂草的常规方法成本高昂，并且在关键阶段无法利用人工会导致严重的产量损失。这种情况使得必须使用除草剂来有效，及时地控制杂草洋葱。另外，保持足够的植物种群是获得更高产量的重要因素，这也影响田间杂草密度。行距对杂草干物质有显着影响，并且与杂草种群呈正相关（Shah and Patel，1995）。植物的空间倾向于改变微气候，这反过来又影响植物的代谢活动，进而影响植物的生长发育。考虑到保持足够的植物种群的重要性以及农民在生长的关键阶段由于劳动力短缺而面临的问题，进行了一项调查，以评估化学除草剂在不同种植密度下对杂草的控制和生产力的效率和经济性。洋葱。
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