A previous field trial showed that marketable yield increased and root-knot nematode populations declined when the swollen roots of sweetpotato were surrounded by a sawdust-based amendment. Further evidence that such amendments provide worthwhile levels of nematode control was obtained in this study. Customised pots filled with an organic amendment or amended soil were kept in a greenhouse or buried in the field for various times and then the nematode-control potential of various treatments was assessed by surrounding the pots with soil infested with Meloidogyne incognita. Swollen root production generally increased, and root-knot nematode populations consistently declined, when sawdust was used as an amendment. The addition of an organic nitrogen source generally improved the level of control. Laboratory and greenhouse assays confirmed that amended soils were biologically suppressive, as root-knot nematode numbers were lower and fewer galls were produced in soil containing decomposing amendments than in soil or sand that had been heated to kill the soil biota. A predatory nematode morphologically similar to Clarkus papillatus was one of the suppressive agents as numbers were very high in some experiments. Mesostigmatid mites in the family Laelapidae and genera Sejus, Protogamasellus, Holaspulus and Gamasiphis were also contributing, while an acarid mite (Rhizoglyphus robini) occurred in high numbers and was observed devouring root-knot nematode juveniles on agar plates. Nematophagous fungi were also involved as three species of nematode-trapping fungi (Arthrobotrys musiformis, A. thaumasia and A. oligospora) and an unidentified fungus that captures nematodes on bulbous hyphal extensions were consistently isolated from amended soils. These results suggest that sawdust-based amendments enhance the nematode-suppressive services provided by a wide range of predators.

中文翻译：

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用有机改良剂的分解带包围甘薯肿胀的根部，可增强线虫抑制作用并减少根结线虫造成的损害

先前的田间试验表明，当甘薯肿胀的根部被锯末基改良剂包围时，可销售的产量增加，根结线虫种群减少。在本研究中获得了进一步的证据，表明此类修正提供了有价值的线虫控制水平。将装有有机改良剂或改良土壤的定制花盆放在温室中或埋在田间不同时间，然后通过用南方根结线虫感染的土壤包围花盆来评估各种处理的线虫控制潜力。当使用锯末作为改良剂时，肿胀的根系产量普遍增加，根结线虫种群持续下降。添加有机氮源通常会提高控制水平。实验室和温室试验证实，经过改良的土壤具有生物抑制作用，因为与已加热杀死土壤生物群的土壤或沙子相比，在含有分解改良剂的土壤中，根结线虫数量较低，产生的瘿虫也较少。一种在形态上与 Clarkus papillatus 相似的掠食性线虫是抑制剂之一，因为在一些实验中数量非常高。Laelapidae 科和 Sejus、Protogamasellus、Holaspulus 和 Gamasiphis 中的中尾螨也有贡献，而螨虫（Rhizoglyphus robini）出现了大量，并观察到在琼脂平板上吞噬根结线虫幼虫。食线虫真菌也作为三种捕捉线虫的真菌（Arthrobotrys musiformis、A. thaumasia 和 A. oligospora) 和一种在球状菌丝延伸部分捕获线虫的不明真菌始终从改良的土壤中分离出来。这些结果表明，基于锯末的改良剂增强了各种捕食者提供的线虫抑制服务。