Abstract Different fertilisers were field tested to investigate whether they (1) suppress the obligate parasitic weed Striga asiatica and the facultative parasitic weed Rhamphicarpa fistulosa, and (2) favour rainfed rice yields under parasitic weed infestation. Four years of experiments were conducted in southwest Tanzania, in a S. asiatica-infested rainfed upland and a R. fistulosa-infested rainfed lowland field. Treatments included sole mineral (NPK or Di-Ammonium Phosphate —DAP— plus urea), organic (cattle manure or rice husk), combinations of mineral and organic fertilisers and a no-fertiliser control. Fertilisers moderately suppressed the obligate parasite S. asiatica, but no correlations between infestation level and soil fertility status were observed. In the lowland field, fertilisers promoted the facultative R. fistulosa, in particular the ones that included organic components. Plant-available phosphorus, exchangeable potassium and soil organic matter content correlated with R. fistulosa infestation levels. Positive fertiliser effects on yields were found in both parasitic weed infested fields, except in years with high S. asiatica infestation levels. Rice husks alone and rice husks or manure combined with DAP and urea increased yields and soil fertility most. We conclude that fertilisation differentially affects the obligate and facultative parasitic weeds of rice systems; obligate parasites may be slightly suppressed, but facultative parasites may even be stimulated. Meanwhile, consistent rice yield increases under parasitic weed infested conditions cannot be obtained with fertiliser application when parasitic weed infestation levels are too high.

中文翻译：

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肥料对水稻兼性和专性寄生杂草的影响不同，只是偶尔提高受侵染田的产量

摘要 田间试验不同肥料以研究它们是否（1）抑制专性寄生杂草独脚金和兼性寄生杂草Rhamphicarpa fistulosa，和（2）在寄生杂草侵染下有利于雨育水稻产量。在坦桑尼亚西南部，在 S. asiatica 出没的雨养高地和 R. fistulosa 出没的雨养低地进行了四年的实验。处理包括单一矿物（NPK 或磷酸二铵 - DAP- 加尿素）、有机（牛粪或稻壳）、矿物和有机肥料的组合以及不施肥控制。肥料适度抑制专性寄生虫 S. asiatica，但未观察到侵染水平与土壤肥力状况之间的相关性。在低地，肥料促进了兼性 R. fistulosa，特别是那些包含有机成分的。植物有效磷、可交换钾和土壤有机质含量与 R. fistulosa 侵染水平相关。在两个寄生杂草侵染的田地中都发现了施肥对产量的积极影响，但在积雪草侵染水平高的年份除外。单独使用稻壳以及稻壳或粪肥与 DAP 和尿素结合使用对提高产量和土壤肥力的作用最大。我们得出结论，施肥对水稻系统的专性和兼性寄生杂草有不同的影响；专性寄生虫可能会受到轻微抑制，但兼性寄生虫甚至可能会受到刺激。同时，当寄生杂草侵染水平过高时，施肥无法在寄生杂草侵染条件下获得一致的水稻产量增加。