Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/8/2008
Publication Date: 5/27/2008
Citation: Balkcom, K.S., Arriaga, F.J., Bergtold, J.S., Mitchell, C., Delaney, D.P. 2008. Nitrogen fertilizer for conservation tillage cotton: Source, rates, and timing. In: Boyd, S., et al, editors. Proceedings of the National Cotton Council Beltwide Cotton Conference, Jan. 8-11, 2008, Nashville, Tennessee. p. 1622-1629. Interpretive Summary: Rye (Secale cereale L.) is a popular choice for experienced growers that utilize conservation systems due to its wide adaptability to soil fertility levels, climate zones, and biomass production, however, in order to maximize the benefits of a conservation system, supplemental N should be applied to enhance biomass production. Researchers from the National Soil Dynamics Laboratory and cooperators from the Agronomy and Soils Department at Auburn University compared different fertilizer sources, rates, and times of application to determine subsequent rye biomass levels. The effect of N supplied to the cover crop was also examined by measuring lint yields. The experiment was conducted during the 2006-2007 growing seasons at the Wiregrass Research and Extension Center, Headland, AL. Data collection included cover crop biomass and lint yields. Rye biomass responded to fall application and increased N rates. Lint yields responded to N supplied to the cover crop as poultry litter, but yields were not maximized compared to N supplied at sidedress. Future work should focus on using poultry litter as an N source for the cover crop with lower cotton N sidedress rates.
Technical Abstract: The expected benefits associated with any type of conservation system in the Southeast require the use of a winter annual cover crop, usually a winter cereal. Rye (Secale cereale L.) is a popular choice for experienced growers that utilize conservation systems due to its wide adaptability to soil fertility levels, climate zones, and biomass production. However, in order to maximize the benefits of a conservation system, supplemental N should be applied to enhance biomass production. An alternative to commercial N applied to the cover crop is poultry litter. No information exists on the optimal rates or time of application to maximize cover crop biomass production and how the potential residual effect of poultry litter affects cotton (Gossypium hirsutum L.) N requirements in a high residue conservation tillage system. Initial results indicate that if growers choose to maximize biomass production by utilizing a form of N fertilizer, regardless of the rate, that fall application would be more beneficial to the cover crop. In 2006, poultry litter applied to the rye cover crop increased cotton lint yields with no additional fertilizer compared to commercial fertilizer. The addition of 90 lb N ac-1 benefited the cotton crop, which was evident by the substantial increase in lint yields observed, regardless of the cover crop N rate. In 2007, regardless of N source, lint yields increased as cover crop N rate increased, but poultry litter improved lint yields compared to commercial fertilizer. At the recommended 90 lb N ac-1 sidedress rate, the difference between sources was not as great, but lint yields following poultry litter were higher. Future work in this area should focus on comparing poultry litter supplied to the cover crop and lower cotton N sidedress rates to current cotton conservation tillage systems that utilize approximately 30 lb N ac-1 to the cover crop and maintain recommended sidedress N rates.