确定杂草防治期的新方法(一)

本文综合杂草生物学、作物与杂草的竞争及经济学三方面的知识，提出了一种确定杂草防治最佳时期的方法。本方法的依据是时间密度当量（ＴＤＥ）概念：指与作物同时萌发并与作物竞争至收获期的杂草密度，该密度下与给定萌发时间、消亡时间和种群密度的杂草引起相同的产量损失。由于处理前后均有杂草萌发，发展了一种考虑杂草萌发的模式，以最小的经济损失决定杂草防治时间的模型。以两个例子表述模拟结果：玉米与苘麻（Ａｂｕｔｉｌｏｎｔｈｅｏｐｈｒａｓｔｉ）竞争；大豆与苋（Ａｍａｒａｎｔｈｕｓｃｒｕｅｎｔｕｓ）竞争。对两种作物使用了包括芽前处理、芽后化学处理及芽后机械处理在内的６种不同的杂草防治策略。模拟结果与假设杂草与作物同时萌发且不考虑不同防治时间影响的边际收益计算的结果进行了比较。不同的防治策略的比较不仅需考虑最大边际收益，也必须考虑它与防治时间的相关性。因为，防治策略的最大边际收益值较低，边际收益曲线较平缓，可以有更灵活的杂草防治时间。

不同耕作方式对烟草—水稻轮作农田杂草种子库的影响

为明确不同耕作方式下烟草—水稻轮作农田杂草种子库的物种组成、季节和空间垂直分布规律。采用杂草种子萌发法,调查烟稻轮作田免耕、翻耕2种耕作模式下烟草—水稻农田0~15 cm土层土壤杂草种子库组成及特征。2017—2018年试验统计结果表明,免耕烟稻轮作田共有杂草13科27种,翻耕烟稻轮作田共有杂草13科25种,有22种杂草在翻耕和免耕烟稻轮作田均有分布。有5种杂草只在免耕田出现,有3种杂草只在翻耕田出现。在试验中发现7种主要杂草种子,其中,马唐、无芒稗和狗尾草是不同季节杂草种子库的共同优势物种。免耕处理下杂草总密度大于翻耕处理下杂草总密度,翻耕处理中优势物种在种子库种子中所占比例高于免耕处理。春季和秋季是杂草种子库杂草种子发生的高峰期。免耕对杂草种子库的垂直分布影响明显,免耕杂草种子主要集中于土壤上层(0~5 cm),翻耕处理对杂草种子库的垂直分布影响很小,翻耕处理下杂草种子库密度没有产生显著性差异。研究结果明确了不同耕作模式土壤杂草种子库的物种组成、季节分布和垂直变化规律,为今后杂草的管理和控制提供理论依据。

Effects of Pb Stress on Seed Germination and Seedling Growth of Two Weed Species Seeds

Objective] The aim was to investigate the effects of Pb stress on seed germination and seedling growth of Chenopodium glaucum and Chenopodium serot-inum L. [Method] With C. glaucum and C. serotinum as the study objects, the ef-fects of different concentrations of Pb on their seed germination and seedling growth, as wel as on the leaf SOD, POD and CAT activity were studied primarily. [Result] The germination potential of both the two kinds of weed seeds increased first and then decreased with the increase of Pb concentration. The germination po-tential of C. serotinum and C. glaucum seeds reached the peak at Pb concentration of 25 and 50 mg/L, respectively. With the increase of Pb treatment concentration, the germination rate, germination index and vigor index of C. serotinum and C. glaucum seeds decreased, and their bud length and root length also reduced gradu-al y. ln overal , the leaf SOD, POD and CAT activity of C. glaucum and C. serot-inum_ seedlings increased first and then decreased with the increased treatment concentration of Pb. The leaf SOD and POD activity of C. glaucum and C. serot-inum seedlings reached the maximum at Pb concentration of 200 and 100 mg/L, respectively, and the leaf CAT activity reached the maximum at Pb concentration of 100 mg/L. [Conclusion] The two Chenopodium species had strong tolerance to Pb stress, and they could be used as alternative accumulator plants of soil Pb contami-nation.

菜地使用化学除草剂应注意的事项

在蔬菜生产中,中耕除草用工占整个菜地管理约30%以上,用化学药物除草,不仅可以防除杂草,减少病虫害的发生,也节省大量的除草用工。因此,使用化学除草是一项投资少、见效快、经济效益好的措施。但在使用化学除草的过程中,还应注意如下几点:1、菜地使用除草剂多采用土壤处理法,必须在播种前或播后芽前进行,施药时间以杂草初生阶段效果好。在杂草长至9厘米以上,或分蘖期后施药效果较差,甚至无效。即使有效也只能是消灭地上部分,而没有除根。2、除草剂土壤处理时要求土地平整,土粒细碎、湿润,创杂草萌发的条件,使杂草萌发一致。

菜地化学除草技术

在蔬菜生产中,中耕除草用工占整个田间管理的40%以上。而化学除草。

种植中药材如何除草

注意事项 化学防除药田杂草应注意以下几个问题: 1、注意化学除草剂的选择性、专一性和时间性,不可误用、乱用除草剂,防止杀死药苗。

Assessment of the Allelopathic Potential of an Invasive Alien Weed Hyptis suaveolens （L,） Poit. on Germination of Oryza sativa L.

Hyptis suaveolens （L.） Poit. is an invasive alien weed commonly known as ＂Bana tulst＂ in Odisha belonging to the family Lamiaceae and widely distributed in different parts of India. The leaves of the plant have been reported to be used as stimulant, carminative, sudorific and also as a cure for parasitic cutaneous diseases besides the crude leaf extract is reported to be used against colic and stomach-ache. The leaves are the source of different alkaloids, terpenes and volatile oils having allelopathic effect. In view of this the present work was carried out with an aim to investigate the allelopathic effect upon germination of rice （Oryza sativa L.）. The result indicated that the higher concentration of the leaf leachate could decrease the percentage of germination besides identified as a potential bio-herbicide.