Forage Species Identity Shapes Soil Biota in a Temperate Agroecosystem

Matthew Kenwood,Samantha Garritano,Denise M Finney

doi:10.3390/su13105689

Abstract

Increasing plant diversity in the perennial phase of pasture-crop rotations is predicted to positively affect belowground productivity and microbial communities and, in turn, augment belowground agroecosystem services including soil health and carbon storage. Using two grass and one legume forage species grown as monocultures and combined in four intercropped combinations, we evaluated how species identity and richness influence belowground productivity, soil microbial communities, and soil C pools. Though grass-legume intercrops demonstrated higher aboveground productivity than component species grown in monoculture, higher species richness was not associated with increased productivity belowground. Root biomass was greatest in tall fescue (Festuca arundinacea Schreb.) monoculture, and intercrops including this species. Species identity was similarly associated with soil microbial community attributes. Orchardgrass (Dactylis glomerata L.) monoculture exhibited lower total microbial abundance and lower bacterial abundance than grass-legume intercrops. Bacterial abundance was also lower in orchardgrass compared to white clover (Trifolium repens L.) monoculture. A common indictor of soil function, the fungal:bacterial ratio, was higher in grass-only than clover-only stands. The prevalence of species-specific impacts on roots and microbial communities in this study suggests that species identity may have a stronger influence than species richness on belowground agroecosystem services from perennial forages in temperate regions.

Highlights

The grass biculture produced less biomass than the Tall fescue (TF) + White clover (WC) and the triculture (Figure 1A), and there was a trend toward lower production in TF + OG compared to OG + WC, but this difference was not statistically significant
With heightened emphasis on engineering agroecosystems to provide services such as enhanced soil health and C storage, an improved understanding of how the identity and number of species present in an agroecosystem influences belowground biota is critical to helping farmers finetune crop selection for expanded service provision
We found that increases in bacterial abundance were associated with the legume, white clover, while a higher F:B ratio was observed in association with grass species

Summary

Introduction

Increasing the capacity of agricultural systems to provide multiple agroecosystem services (i.e., the benefits humans derive from agriculture such as food production; soil, water, and air quality regulation; and support for nutrient cycling) is critical to meeting the needs of the global population while mitigating negative environmental impacts of agriculture [1]. Pasture-crop rotations that incorporate multiple years of a perennial forage within row crop production can enhance agronomic crop yield while improving water and soil quality [3]. Agroecosystem services expected from perennial forages in a pasture-crop rotation, such as soil carbon (C) sequestration and soil health, are mediated by plant roots and soil microbes [4], yet few studies on the short-term effects of crop selection practices on soil biota have been conducted.

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