Pedosphere 30(6): 791--800, 2020
ISSN 1002-0160/CN 32-1315/P
©2020 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Responses of soil nematode community to monoculture or mixed culture of a grass and a legume forage species in China
Yingying YE1,2,4, Yichao RUI3, Zhaoxia ZENG1,2, Xunyang HE1,2, Kelin WANG1,2, Jie ZHAO1,2
1Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125(China)
2Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences, Huanjiang 547100(China)
3Department of Soil Science, University of Wisconsin-Madison, Madison WI 53705(USA)
4University of Chinese Academy of Sciences, Beijing 100049(China)
      Mixed cultivation of fast-growing grasses and nitrogen (N)-fixing legumes for forage production is widely considered effective for obtaining sustained high forage yields without depleting soil N levels. However, the effects of monoculture and mixed culture of these species on soil food webs are poorly understood. In this study, soil nematode communities were examined as indicators of the soil food web structure of monoculture and mixed culture of grass and legume at three N levels, i.e., 338 (low), 450 (moderate), and 675 (high) kg N ha-1 year-1, across 2 years in wet and dry seasons, using the grass Paspalum wetsfeteini and the legume Medicago sativa (alfalfa), both commonly cultivated worldwide. Repeated-measures analysis of covariance showed that compared with grass monoculture, legume monoculture and grass-legume mixture increased abundances of herbivorous, bacterivorous, and fungivorous nematodes in the soil food web under the low and moderate N fertilization levels. Principal response curve results showed that the abundance of Helicotylenchus, a plant parasite, was significantly higher under legume monoculture than other planting systems at the low N fertilization level. Structural equation model analysis indicated that the legume increased bacterivore abundance, while increasing N fertilization decreased omnivore abundance. The legume might increase the quantity and quality of food resources for soil biota, resulting in the bottom-up control of soil nematode communities. Our results indicate that targeted control of a soilborne pathogen, Helicotylenchus, is required in alfalfa-based planting systems. In addition, high inorganic N application, which is detrimental to legume-rhizobia symbiosis, nullified the otherwise positive effects of legumes on soil nematodes.
Key Words:  bacterivore,bottom-up control,fertilization,fungivore,herbivore,nitrogen,soil food web,soilborne pathogen
Citation: Ye Y Y, Rui Y, Zeng Z X, He X Y, Wang K L, Zhao J. 2020. Responses of soil nematode community to monoculture or mixed culture of a grass and a legume forage species in China. Pedosphere. 30(6):791-800.
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