Nitrogen In Soil Growing Toxic and Novel Endophyte Infected Tall Fescue as Influenced by Earthworms.

Earthworm species inhabiting different ecological niches may have different impacts on N cycling. In addition, the infection of tall fescue with the toxic endophyte (Neotyphodium coenophialum) may negatively influence consumption compared to novel endophyte infected tall fescue.  Understanding differences between earthworm species and feeding preferences will be important in understanding the broader impacts for earthworms on nutrient cycling in grassland ecosystems. A laboratory incubation was conducted using 10-cm dia., 30-cm long PVC cores filled with 20 cm of Captina silt loam growing toxic or novel endophyte infected tall fescue with toxic or novel tall fescue litter on the soil surface, respectively. Treatments included no-worm, cores with two Diplocardia sp. (native endogeic worms), cores with two Lumbricus terrestris (non-native anecic worms), and cores with one each Diplocardia sp. and Lumbricus terrestris. Microbial, dissolved and total soil N concentrations were measured in all treatments for 6 weeks after litter additions. Furthermore, toxic litter was labeled with ¹⁵N and ¹⁵N concentrations in the soil, worms, and fescue were measured. The objective of this study was to determine if the absence, presence or combined presence of native (endogeic) and non-native (anecic) earthworms resulted in detectable differences in nitrogen pools.