Perennial grain crop roots and nitrogen management shape soil food webs and soil carbon dynamics

Abstract

Perennial grain crops may confer greater ecosystem services relative to annual row crop systems due to their extensive roots systems and year-round ground cover. However, less is known about the extent to which perennial grain crops affect food web dynamics and soil carbon (C) cycling over time. Furthermore, many mechanistic questions remain regarding the influence of root quantity and quality on soil biological communities and C cycling function. In this study, we quantified root biomass and quality, bacterial and nematode community structure, and labile soil C pools of perennial intermediate wheatgrass [Thinopyrum intermedium (Host) Buckworth and Dewey] and annual winter wheat (Triticum aes L.) across three nitrogen (N) management systems (Organic, Low inorganic N, High inorganic N). After 4 years, the perennial grain crop had significantly greater root quantity and permanganate oxidizable carbon (POXC) relative to annual wheat. Mineralizable C was similar between the two plant systems but differed by N management. Perenniality more than management influenced nematode community structure and function; perennial grains increased the structure index (a measure of trophic complexity) by 55% compared to annual wheat. Both plant type and management influenced bacterial communities, but not until the final year of the experiment. Our findings demonstrate that established perennial grain crops increase labile soil C and support more highly structured and complex food webs relative to annual cropping systems.