Abstract Long-term intensive rice monoculture, triple rice cultivation (rice crops are cultivated three times per year) in the Mekong Delta, Vietnam, causes a reduction in topsoil quality. Rotating rice with an upland crop in a tropical paddy field may improve the soil physicochemical properties but effects on the soil nematode community are unknown. This study was conducted in a triple rice field to evaluate the responses of the nematode community to a crop rotation (the first rice in a year was replaced with sesame and soybean, and the second and third crops were rice) and to organic amendment. The experiment was based on a split-plot design with two factors that were crops (main factor, n = 3) and compost amendment (sub-factor, n = 3). The crops were rice, soybean, and sesame and the sub-factors were cow manure plus rice straw compost, sugarcane compost, and no amendment. Soil samples were taken at harvest of the first crops in topsoil (0–10 cm) and subsoil (10–20 cm) in 2017 and 2018. In 2018, the abundance of free-living nematodes (FLN), which were dominated by bacterivores and fungivores, was greater in upland crops, while that of plant-parasitic nematodes (PPN) was greater in paddy rice. In particular, the density of the most predominant PPN genus, Hirschmanniella, was lower in upland crops than in paddy rice. Cultivation of sesame also reduced the number of the second predominant PPN genus, Bitylenchus, resulted in an increase in the ratio of the free-living to plant-parasitic nematodes. The diversity evenness index (J), Shannon-Wiener (H′) and Hill's indices increased in upland crops compared to those in rice fields in 2018. Crop rotation with sesame or soybean in a paddy field enhanced abundance and biodiversity of FLN and suppressed PPN and thus can be proposed for agricultural sustainability.

中文翻译：

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越南湄公河三角洲稻田种植制度和土壤改良剂对线虫群落的影响及其与土壤理化性质的关系

摘要 越南湄公河三角洲的长期集约化水稻单一栽培、三重水稻种植（水稻作物每年种植三次）导致表土质量下降。在热带稻田中轮作旱作水稻可能会改善土壤理化性质，但对土壤线虫群落的影响尚不清楚。本研究在三重稻田中进行，以评估线虫群落对轮作（一年中的第一次水稻被芝麻和大豆取代，第二次和第三次作物是水稻）和有机改良剂的反应。该实验基于具有两个因素的裂区设计，即作物（主要因素，n = 3）和堆肥改良物（次因素，n = 3）。作物为水稻、大豆和芝麻，子因子为牛粪加稻草堆肥，甘蔗堆肥，没有修改。2017 年和 2018 年在表土（0-10 厘米）和底土（10-20 厘米）收获第一批作物时采集了土壤样品。 2018 年，以食菌动物为主的自由生活线虫 (FLN) 的丰度和食真菌，在旱田作物中更大，而植物寄生线虫（PPN）在水稻中更大。特别是，陆地作物中最主要的 PPN 属 Hirschmanniella 的密度低于水稻。芝麻的种植还减少了第二个主要 PPN 属 Bitylenchus 的数量，导致自由生活线虫与植物寄生线虫的比例增加。与稻田相比，2018 年旱地作物的多样性均匀度指数 (J)、香农-维纳 (H') 和希尔指数有所增加。