Responses of the soil nematode community to management of hybrid napiergrass: The trade-off between positive and negative effects

• Soil nematodes were affected more by fertilization and irrigation than by cutting.
• Fertilization had both positive and negative effects on soil nematode community.
• A hypothetical trade-off between the positive and negative effects was proposed.
• Additional water applied in irrigation was detrimental to soil nematodes.
• Soil health benefits from an optimal combination of fertilization, irrigation and cutting.

An orthogonal experiment (form L16(45)) was used to investigate how the soil nematode community (density, diversity, and faunal structure) and soil health were affected by hybrid napiergrass management. The experiment included four levels of the each of the following main factors: nitrogen fertilization, cutting frequency, cutting intensity, and irrigation. The soil nematode community was affected more by nitrogen fertilization and irrigation than by cutting frequency and cutting intensity. Hybrid napiergrass develops a large root system and the carbon stored in the roots might have buffered any adverse effects of cutting on soil nematodes in the present study. The responses to fertilization indicated that fertilization had both positive and negative effects on the soil community and that the net effect depended on the level of fertilization. Additional water applied in irrigation was detrimental to soil nematode communities in that it might reduce the oxygen content of soil and also increases the potential for the leaching of nutrients from soil. Additionally, we suggest that moderate N fertilization (460 kg ha−1 yr−1), moderate irrigation (one time yr−1 during the dry season), and cutting (three times per year at 20 cm height) will maintain soil health and provide substantial hybrid napiergrass yields.