Biochar Effects On Switchgrass Establishment and Water Quality.

Intensive biomass production in support of emerging bioenergy systems could increase nonpoint-source sediment and nutrient losses and impair surface and groundwater quality. Recycling biochar, a charcoal byproduct from pyrolysis of biomass, provides potential sources of mineral nutrients and organic carbon for sustaining biomass productivity and preserving soil and water.  Yet, research is needed to verify that recycling of pyrolysis biochars will enhance soil and environmental quality similar to black carbon or biochar derived from burning of biomass in tropical or Terra Preta soils.  The experimental design of this study consisted of 3 replications and four biochar rates (0, 4, 16, and 64 Mg ha^-1) incorporated in both a sandy loam and clay soil with and without fertilizer sources of N, P, and K. The sandy loam and clay soils were studied in separate experiments within a set of 24 box lysimeters.  Physical and chemical properties of biochar derived from corn stover were quantified before the soil was amended and packed within box lysimeters for seeding of switchgrass. Simulated rain was applied at 50% and 100% establishment of switchgrass for each soil type.  Runoff and leachate were collected and analyzed for total and dissolved N and P and organic C.  After the second rain event, each soil type and the accumulated switchgrass was sampled and analyzed.  The sandy loam amended with 64 Mg ha^-1 of biochar resulted in only a 15% seed germination rate of switchgrass, while the clay had a seed germination rate of over 60% with the same rate of biochar.  Total runoff losses of sediment and biochar were significantly higher in the sandy loam versus the clay soil for all treatments.  In both soil types, increasing biochar rate contributed to an increased concentration of dissolved reactive P (DRP) in runoff collected during the simulated rainfall events.