Impact of Biochar Addition on Nitrogen Dynamics and Growth of Three Bioenergy Grasses.

Switchgrass, big bluestem, and Indiangrass are perennial (C₄) warm season grasses that are native to North America and are desirable as biomass energy crops. They are highly adaptive to diverse growing conditions such as marginal lands with low soil fertility. Biochar is a carbon-rich material produced by thermal decomposition of biomass under limited supply of oxygen (O₂), and at relatively low temperatures (<700 °C) and can be applied as a material for improving soil productivity, filtration of soil water, or carbon (C) storage. We hypothesize that biochar application with N fertilizers to low fertility soils will increase biomass production for switchgrass, indian grass, and big blue stem. We conducted a greenhouse experiment to evaluate the effects of biochar amendments with different N rates for soil quality, N-use efficiency and the biomass yield of switchgrass, Indian grass, and big bluestem. We used a completely randomized block design (RCBD) with four blocks. The potting media was prepared by homogenously mixing Promix^® starter mix and white sand at a volume ratio of 3:1. Biochar was mixed homogenously at 0, 5, 20, 35 (t/ha) rates with the potting mixture. Four nitrogen application (0, 60, 120, 180 kg/ha) rates were used. Biomass yield and plant physiological properties (photosynthesis rate) were measured along with nutrient uptake by plant tissues. Soil chemical and physical properties were measured. Results showed that biochar and nitrogen rate both can influence plant growth and function. Information gained from this study can be utilized in making recommendation for biochar application in marginal soils for biomass crops.