Grass Biomass Management for Bioheat.

Grass biomass for residential and light industrial space heating has the potential to be a local closed-loop energy system for rural areas. Grass biomass for bioheat should be relatively low in total ash, N, K, Cl, and S content. The impact of organic matter or commercial fertilizer application on grass biomass production, composition, and soil N, P and K dynamics needs to be investigated. We selected three species with high yield potential (switchgrass, reed canarygrass and tall fescue) and focused on the impacts of soil type and fertility management on yield and composition of these grass species. Six replicates each of switchgrass (Cave-in-Rock), reed canarygrass (Rival) and endophyte-infected tall fescue (KY-31) were established on a sandy site and on a clay soil. Six treatments applied to each block included: 1) Check, 2) Composted dairy manure, 3) Dairy manure, 4) N fertilizer, 5) N, P fertilizer, 6) N, P, K fertilizer. Fresh dairy manure and composted dairy manure were applied at equal quantities of organic N. Nitrogen (112 kg N/ha), P (11.3 kg P/ha), and K (55.8 kg K/ha) were applied to cool-season grasses at spring green-up. Nitrogen (84 kg N/ha) was applied to switchgrass at spring green-up, and N (56 kg N/ha) was applied to cool-season grasses following July harvest. Cool-season grasses were harvested twice and switchgrass was harvested once per season. Forage concentration of ash, N, K, and Cl were all greatly affected by treatment and species, but not by soil type. Over three years, switchgrass produced the highest yields, averaging 8595 kg/ha on the sand site and 10,191 kg/ha on the clay site, with minimal yield response to treatments. Cool-season grasses with manure application produced similar yields to the NPK commercial fertilizer treatment. However, compost-treated cool-season grasses yielded similarly to checks, averaging 47% lower yields than fresh manure in 2011.