Panicum virgatum is a potential biofuel crop that is tolerant of many different soils, one reason it is a desirable biofuel crop. Previous experiments by the authors have shown that the soil community and P. virgatum itself are resilient to nitrogen fertilizer additions in good agricultural soil (collected from a farm in Freehold, NJ). However, good agricultural soil is not representative of more stressful soils in which switchgrass may be grown. Ideally, biofuel corps will be grown on land that is not useful for growing food crops. In less nutrient-rich soils, P. virgatum may show a greater response to changes in the soil conditions. We ask: does P. virgatumgrowth respond to soil manipulations (adding nitrogen fertilizer and commercial mycorrhizal inoculum) differently in three different soils—good agricultural soil, marginal agricultural soil, and sand from the New Jersey Pine Barrens, where switchgrass grows in disturbed sites. We conducted a 3x2x2 factorial design greenhouse experiment to test the hypothesis that switchgrass biomass yields will respond to manipulations of the soil community.
After the summer growing season, above-ground and below-ground biomass were collected and weighed. Roots were sub-sampled for mycorrhizal colonization. Soil sub-samples were used for Biolog MicroPlate assessment of bacterial community, total nematode counts and soil arthropod community assessment.
Results differed by soil type, but not by fertilizer or mycorrhizal inoculum treatments. Principle Components Analysis of well color development in the Biolog MicroPlates shows differences due to soil type but not by other treatments. Soil arthropod morphospecies differed by soil type but not by other treatments. Nematode numbers differed significantly (p=0.000006) by soil type, but not by the other factors. Mycorrhizal colonization differed by soil type. There were differences in root mass by soil type (p=0.0044 level), and by fertilizer (p=0.09). Above-ground biomass differed significantly by soil type but not by the other treatments. These results show the resilience of the soil community to perturbation across all soil types.