Biodiv Sci ›› 2018, Vol. 26 ›› Issue (12): 1296-1307.DOI: 10.17520/biods.2018245

• Original Papers • Previous Articles     Next Articles

Nitrogen levels modify earthworm-mediated tomato growth and resistance to pests

Yu Zhang1, Zhenggao Xiao1, Linhui Jiang1, Lei Qian2, Xiaoyun Chen1, Fajun Chen2, Feng Hu1, Manqiang Liu1,*()   

  1. 1 Soil Ecology Laboratory, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095
    2 College of Plant Protection, Nanjing Agricultural University, Nanjing 210095
  • Received:2018-09-12 Accepted:2018-11-19 Online:2018-12-20 Published:2019-02-11
  • Contact: Liu Manqiang
  • About author:# 同等贡献作者 Contributed equally to this work

Abstract:

Excessive chemical nitrogen (N) fertilizer application causes serious environmental problems and affects the ecosystem services that depend on soil biota. Earthworms improve soil fertility and plant productivity via activities such as feeding, burrowing and casting, and alter the relationships between crop plants and pests by modifying plant primary and secondary productivity. In order to mechanistically understand the functional roles of soil fauna in ecosystem services, a pot experiment using tomatoes (Lycopersicon esculentum) was conducted in a greenhouse. The study used a complete factorial design that manipulated earthworm (Metaphire guillelmi) abundance, western flower thrips (Frankliniella occidentalis) and N input. Results showed that under low N-input conditions, earthworms significantly reduced shoot and root biomass and shoot soluble sugar content, and increased shoot jasmonic acid content (by 6 times) and shoot salicylic acid content (by 3 times), compared to treatments without earthworms. This was accompanied by the decrease of thrips abundance by 58%, indicating a remarkable suppression of aboveground pests by earthworms. However, under high N-input conditions, earthworm presence did not affect the contents of shoot jasmonic acid or shoot salicylic acid or thrips abundance by the end of the experimental period (45 days). The earthworm-mediated responses of plant nutrition (shoot soluble sugar and shoot total nitrogen) was significantly positively correlated with thrips abundance, whereas defense (shoot jasmonic and salicylic acid) was significantly negatively correlated. Changes to soil N availability due to N fertilizer input can shift the direction of earthworm-mediated plant resistance against herbivores by altering plant resource acquisition and secondary defense. Effects of earthworms on plant growth and resistance depend on soil management practices such as N fertilizer application. A comprehensive understanding of the roles of soil biota in mediating plant growth requires knowledge of the multifaceted relationships among soil management, soil fauna, and plant pathogens.

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Key words: soil fauna, plant chemistry, pests, aboveground-belowground, ecosystem service