Impact of Long-Term Cultivation of Alfalfa, Bermudagrass, Switchgrass, and Winter Wheat On Soil Biogeochemical Properties.

With increasing interest in plant derived biofuels as an alternative source of energy, accessing the effect of bioenergy crop production on soil quality is vital for preserving sustainability of the production system. Limited information is available on how the cultivation of prairie grasses such as switchgrass (Panicum virgatum L.) would impact soil’s capacity to cycle nutrients and sustain production.  We conducted a comparative study to evaluate effects of cultivating switchgrass, alfalfa (Medicago sativa L.), bermudagrass (Cynodon dactylon L.), and winter wheat (Triticum aestivum L.) on basic soil properties and activities of soil enzymes involved in cycling carbon, phosphorous, and nitrogen.  Sixty soils from these four soil systems at three soil depth were evaluated. When compared with winter wheat cultivation, long-term (>10 years) switchgrass cultivation led to steady carbon dynamic and equivalent or greater capacity to cycle nutrients based on evaluations of soil enzyme activities.  However, when compared with those under cultivation of alfalfa and bermudagrass, soils under winter wheat and switchgrass had significantly lower soil organic carbon contents and activities of enzymes involved in cycling multiple nutrients. Results suggested that cultivation history is a predominant factor affecting soil biogeochemical properties. Based on principle component analysis of all variables tested, four clusters corresponding to the four soil ecosystems are revealed.  Winter wheat and switchgrass soil ecosystems are closely related and discriminated by similar soil variables.