Evaluation of sweet sorghum planting density and minimal nitrogen input, under irrigated and non-irrigated conditions, for bioethanol feedstock production

ABSTRACT

Sweet sorghum is a feedstock for bioethanol and is grown on a few hectares in the USA. Research was conducted to optimize the cultural management recommendations for sweet sorghum-based bioethanol production. Experiments were conducted using the ‘Top 76-6’ cultivar to evaluate the effect of nitrogen rate (84 and 168 kg N ha⁻¹) and seeding rate (114, 143, 191, 286 and 571 kg ha⁻¹) or population density (41,000, 51,100, 68,200, 10,2500 and 205,000 plants ha⁻¹) on biomass and sugar yield with or without irrigation. In 2012, we evaluated seeding rate and nitrogen effects. With irrigation, the lowest seeding rate produced the most biomass (44,588 kg ha⁻¹), equivalent to 3.25 Mg ha⁻¹ sugar. Biomoass increased with more nitrogen across seeding rates. Without irrigation, neither seeding rate nor N rate impacted biomass or sugar yield. In 2013 and 2015, biomass ranged from 49,000 to 92,000 kg ha⁻¹ with irrigation and 45,000 to 54,000 kg ha⁻¹ without irrigation. The greatest biomass (∼49,000 to 54,000 kg ha⁻¹) was obtained at the two highest population densities. Applying more N had no effect on biomass regardless of population density, except in 2013 without irrigation. With irrigation, optimum productivity can be achieved at low population density with minimum nitrogen input.

KEYWORDS:

• Biofuel feedstock
• irrigation
• population density
• seeding rate
• sugar yield

Acknowledgements

The authors are grateful for the assistance provided by Seth Abugho, Mariccor Batoy, Caroline Bevilacqua, Leopoldo Estorninos, Jr., Linda Martin, Fernando Martini, Fernando Ramirez, Ana Carolina Roso, Reiofeli Salas, Shilpa Singh, Hussain Tahir, Teal Penka and Te-Ming Tseng in establishing the experiments and/or collecting data.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was partially supported by the Department of Energy (DOE) Start-up Grant to the University of Arkansas Agricultural Research Station, 2009–2012, under Project No. US/DOE/DE-FG36-08GO88036-MidSouth/Southeast BioEnergy Consortium.