Switchgrass Biomass Yield and Quality with Multiple Fertilizer Applications and Harvest Dates.

Switchgrass is an important warm season native grass for biomass and forage production in the U.S. The objective of this research was to determine the effect of fertilizer type (conventional, manure, and biosolids) and rate on switchgrass biomass yield and quality. Fertilizers were added at 0, 33, 66, 99, and 132 kg ha^-1 on a N equivalent basis on established stands of Kanlow switchgrass in three NE Kentucky counties. Soils across the three locations ranged from recently cleared forestland (low ph, P, and K) to productive cropland (high pH, P and K). Forage quality and biomass yield were measured June, November, and March to stimulate a hay harvest and two timings for biomass harvest. Preliminary results showed that forage quality in June was 7 to 12.5% CP and adequate ADF and NDF for an average quality grass hay. Biomass yield in November showed a linear response to N rate with the greatest effect on the poorest soil and ranged from 2,500 to 28,000 kg ha^-1. The range in biomass yield was similar across the fertilizer types. In conclusion, these results show that switchgrass provides adequate forage quality when harvested in June and biomass yields are responsive to N applications regardless of fertilizer type.