Additive effects of dung amendment and plant species identity on soil processes and soil inorganic nitrogen in grass monocultures

Abstract

Plant species can exert a strong influence on soil processes. The aim of this field study was to examine the interactive effects of plant species identity and dung amendment on key soil properties related to carbon (C) and nitrogen (N) cycling. Monocultures of three co-occurring grass species (Dactylis glomerata, Lolium perenne, Festuca rubra) with contrasting nutrient acquisition strategies were examined. Soil CO2 fluxes, leaf litter decomposition, C and N storage in soil and soil microbes were measured in plots with and without dung addition. Four months after dung addition, soil sampled from plots was used in a greenhouse bioassay experiment to assess soil fertility. Dung addition increased CO2 fluxes from soil irrespective of plant species; increased leaf litter mass loss and C and N stocks in soil and microbial biomass were also observed. Bioassay results confirmed dung-induced increases in soil fertility. Significant plant species’ effects were found for soil CO2 fluxes, soil inorganic N content, leaf litter mass loss and bioassay seedling root: shoot ratio. Nevertheless, dung effects showed no significant interactions with plant species identity on any of the soil variables examined. Soil responses to dung show additive effects with grass species identity, but are not clearly linked to plant nutrient acquisition strategy in this temperate study system. High nutrient inputs may buffer plant-soil interactions against variation in plant nutrient acquisition strategies.