Nitrogen Fertilization of C 4 Grasses Grown for Bioenergy

1. Nitrogen Fertilization of C4 Grasses Grown for Bioenergy Heather Engbers1, Bill Deen1 & Doug Young2 1Department of Plant Agriculture, University of Guelph, Guelph, ON, N1G 2W1, Canada 2 Ridgetown Campus, University of Guelph, Ridgetown, ON, N0P 2C0, Canada Results: Introduction: One of the most important factors for the efficient growth of plants is meeting nutrient requirements while minimizing losses. Plants that can efficiently absorb and utilize nutrients can greatly enhance the use of applied fertilizers, thus reducing costs and potential environmental damage. C4 perennial grasses are of particular interest for bioenergy production due to their high nutrient use efficiencies and low input costs. Research on several C4 grasses has shown that in general the response of applied N to yield and other macronutrient concentrations decreases with increasing supply but finding Ontario specific optimal N application rates is essential. The main objective of this study was to investigate the effect of N fertilization on yield, and P and K concentrations and removal across several C4 perennial grass species and cultivars during the initial 3 years of establishment. • Key points: • No variety effects on yield • Spring yields reduced by 10-42% relative to fall yields • Significant N response by peak fall biomass except the miscanthus at the Ridgetown location possibly due to low rainfall • P concentration of plant tissue not affected by N rate • P removal ranged from 1-11 kg ha-1 independent of N rate • K concentration of plant tissue not affected by N rate • K removal rates ranged from 10-65 kg ha-1 independent of N rate • K concentrations reduced significantly by spring harvest timing Switchgrass Miscanthus Elora Yield (kg ha-1 @ 0%moisture) Ridgetown Elora Materials and Methods: • The study was conducted at 2 locations, Elora (silt-loam) and Ridgetown (clay-loam), Ontario, where grasses were planted in June 2008. The experiment is a split-split block experiment with three replicates. Species is the main plot factor, fertilizer is the split block and harvest timing is the split-split block factor. • Species: • Miscanthus • 2 M. sinensis and M. sacchariflorus crosses: • Nagara and Amuri • 2 Miscanthus x giganteusgenotypes: • M1 Select and Polish • Switchgrass (Panicumvirgatum L) • Shelter and Cave-in-Rock • Nitrogen rates (as ammonium nitrate spring applied): • 0 kg N ha-1 • 40 kg N ha-1 • 80 kg N ha-1 • 160 kg N ha-1 • Biomass yield was harvested in the fall or spring for two miscanthus (Nagara and Amuri) and two switchgrass varieties (Cave-in-Rock and Shelter).  For the spring harvest, the miscanthus was left standing over winter while the switchgrass was mowed and windrowed in the fall. • The miscanthus was planted as plugs generated from rhizomes while the switchgrass was planted from seed. The miscanthus plugs were planted at a density of 2 plants m-2 and the switchgrass was planted at 50.39 kg ha-1PLS. P Concentration (g/ kg dry wt) Ridgetown Elora K Concentration (g/ kg dry wt) Ridgetown Kg N ha-1 Conclusion: Miscanthus and switchgrass varieties are available that will survive Ontario winters.  Nitrogen fertilizer is required to increase yields for 2nd year production of both miscanthus and switchgrass.  N fertilization had little effect on P and K tissue concentrations, but did alter P and K removal rates through its impact on yield. Nitrogen Rate (kg/ha) Figure 1- Yield and concentration of P and K in Miscanthus(mean result of var. Nagara and Amuri) and Switchgrass (mean result of var. Shelter and Cave-in-Rock) for 2nd year biomass harvested fall (2009) and spring (2010) Acknowledgements: Funding and support for this project was provided by the Ontario Ministry of Agriculture, Food and Rural Affairs. November 2010