Submitted to: Cotton Research and Extension Report
Publication Type: Experiment Station
Publication Acceptance Date: 2/15/2008
Publication Date: 3/15/2008
Citation: Balkcom, K.S., Arriaga, F.J., Mitchell, C.C., Delaney, D.P., Bergtold, J.S. 2008. Nitrogen fertilizer source, rates, and timing for a cover crop and subsequent cotton crop. Cotton Research and Extension Report. No. 32. p. 23-25. Interpretive Summary:
Technical Abstract: The objectives were to compare N fertilizer sources, rates, and time of application for a rye winter cover crop to determine optimal biomass production for conservation tillage production, compare recommended and no additional N fertilizer rates across different biomass levels for cotton, and determine the effect of residual N applied to the cover crop across two N fertilizer rates for cotton. Nitrogen sources, rates, and time of application were implemented at the Wiregrass Research and Extension Center (WREC) in Headland, AL. Biomass cover treatments were arranged in a split-split-plot design with 4 replications. At cotton planting, the eight row plots were split with one side receiving 90 lb N ac-1 at sidedress and the other side receiving no additional N. Biomass levels measured in 2007 produced a timing X rate interaction (Pr > F = 0.0440), which indicates that biomass levels increased with fall application of N (Fig. 1). Timing of N fertilizer had no effect on measured biomass levels during the previous year of this study, but biomass levels following fall applied N averaged over sources and rates for both crop years indicate 25% higher biomass levels compared to spring applied N. This would indicate that if growers choose to maximize biomass production by utilizing some form of N fertilizer that fertilizer would be more beneficial to the cover crop if applied in the fall. The residual effects of the poultry litter are apparent based on higher lint yields measured following on poultry litter applied to the cover crop. However, regardless of N source, lint yields increased as cover crop N rate increased, but poultry litter improved lint yields compared to commercial fertilizer. When the recommended sidedress rate was used, the difference between sources was not as great, but lint yields following poultry litter were again higher. The data also showed there is no advantage to cover crop N rates greater than 30 lb N ac-1 as commercial fertilizer or 1 ton ac-1 as poultry litter when 90 lb N ac-1 is supplied at sidedress to the cotton. Future work in this area should focus on comparing poultry litter supplied to the cover crop combined with lower cotton N sidedress rates to the current cotton conservation tillage systems that utilize approximately 30 lb N ac-1 to the cover crop and maintain recommended sidedress N rates may be warranted. These scenarios could maximize biomass, maintain yields, and decrease costly commercial N use.