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United States Department of Agriculture

Agricultural Research Service

Research Project: SOIL PROCESSES IN PRODUCTION SYSTEMS THAT INCORPORATE BIOFUEL FEEDSTOCKS INTO SOUTHEASTERN AGRICULTURE

Location: Southeast Watershed Research

Title: Production of napiergrass as a bioenergy feedstock under organic versus inorganic fertilization in the Southeast USA

Authors
item Knoll, Joseph
item Anderson, William
item Malik, Ravindra -
item Hubbard, Robert -
item Strickland, Timothy

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 21, 2013
Publication Date: April 10, 2013
Citation: Knoll, J.E., Anderson, W.F., Malik, R., Hubbard, R.K., Strickland, T.C. 2013. Production of napiergrass as a bioenergy feedstock under organic versus inorganic fertilization in the Southeast USA. BioEnergy Research. 6:(3), 974-983. http://link.springer.com/article/10.1007/s12155-013-9328-110.1007/s12155-013-9328-1.

Interpretive Summary: Napiergrass (also called elephantgrass) is a high-yielding perennial biomass crop that is well adapted to the Southeast USA where poultry litter is readily available. Fertilization with either poultry litter or inorganic fertilizer (N,P,K = 100, 40, and 80 kg ha-1) over four years on a non-irrigated Tifton loamy sand resulted in dry matter production that ranged from 6 to 31 Mg ha-1 yr-1. For the first two years, dry matter (DM) yields did not differ among treatments, but in the third and fourth years, yields declined in all treatments and were lowest in the control treatment. In general, N removal exceeded the amount applied, suggesting that higher application rates may be necessary to maintain yields. There was no indication that P was limiting and results demonstrated that napiergrass can remove some of the excess P from applied litter. Potassium availability was not limited over the four year study but may have been approaching deficit levels. Total soil C increased by an average of 3178 kg ha-1 among the three fertilizer treatments indicating that biofuel production from napiergrass is likely to be carbon-positive relative to petroleum.

Technical Abstract: Napiergrass (Pennisetum purpureum Schum.) is a high-yielding perennial biomass crop that is well adapted to the Southeast USA where poultry litter is readily available. This research was conducted to compare biomass production and nutrient utilization of napiergrass fertilized with either poultry litter or inorganic fertilizer. Each spring approximately 100 kg ha-1 of N, 40 kg ha-1 P, and 80 kg ha-1 K was applied as poultry litter or equivalent inorganic fertilizer. Biomass was harvested each winter after senescence. For the first two years, dry matter (DM) yields did not differ among treatments, but in the third and fourth years, yields declined in all treatments and were lowest in the control treatment. Biomass N concentration and N removal were greatest in the inorganic treatment. In general, N removal exceeded the amount applied, suggesting that higher application rates may be necessary to maintain yields. Biomass P concentration and total P uptake were greatest in the litter fertilized treatment, demonstrating that napiergrass can remove some of the excess P from applied litter. Soil cores were taken periodically to assess changes in soil properties. After two years of production soil pH in the surface layer (0–15 cm) was lower in the inorganic treatment than in the other treatments. After four years total soil C had increased by an average of 3178 kg ha-1 though fertilizer treatments did not differ. Yield declined in all treatments after four years and N supplementation is recommended for production in upland fields.

Last Modified: 10/20/2014
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