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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #149886
Title: NITROGEN MANAGEMENT FOR CONSERVATION-TILLED COTTON FOLLOWING A RYE COVER CROP

Author
item REITER, MARK - AUBURN UNIVERSITY
item Reeves, Donald
item BURMESTER, CHARLES - AUBURN UNIVERSITY

Submitted to: International Soil Tillage Research Organization Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2003
Publication Date: 7/13/2003
Citation: Reiter, M.S., Reeves, D.W., Burmester, C.H. 2004. Nitrogen management for conservation-tilled cotton following a rye cover crop. International Soil Tillage Research Organization Proceedings, July 14-18, 2004, Brisbane, Australia. 2003 CDROM.

Interpretive Summary: High-residue conservation tillage systems improve soil quality and reduce soil erosion, but may alter cotton nitrogen (N) management recommendations. We evaluated nitrogen sources, rates, application methods, and timing for conservation-tilled cotton grown with a heavy rye cover crop on a silt loam soil in northern Alabama. We found cotton nitrogen requirement was increased by 30 pounds of nitrogen per acre (lb N/A) compared to conventional tillage systems. At current prices for ammonium nitrate and urea-ammonium nitrate (UAN), the most efficient and economical practice for cotton grown in high-residue conservation systems would be to apply 120 lb N/A as UAN in a banded application at planting. Using 120 lb N/A, at a cost of $0.19/lb N for UAN ($22.80/A) and $0.28/lb N for ammonium nitrate ($33.60/A), producers can save $10.80/A using UAN rather than ammonium nitrate; for a total savings of $1.9 million in annual fertilizer costs for cotton grown in the Tennessee Valley region. Applying all nitrogen at-planting saves trips across the field, reducing operating costs and soil compaction. Farmers, extension agents, environmental groups, and fertilizer industries are interested in knowing the best way to apply nitrogen in an economic manner while being a responsible steward to the environment.

Technical Abstract: Over 70% of the more than 100,000 ha of cotton (Gossypium hirsutum L.) in the Tennessee Valley of northern Alabama, USA, is currently produced using conservation tillage systems with cereal cover crops. Decreased N efficiency, as a result of N immobilization and/or ammonia (NH3) volatilization in these high-residue systems, requires development of new N fertilizer recommendations. We conducted a replicated 3-year field study (2000-2002) on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudult) to test a factorial arrangement of N source [ammonium nitrate (AN) and urea-ammonium nitrate 32% (UAN)], N rates (0, 45, 90, 134, and 179 kg N ha-1), N application timing (all at-planting and 50-50 split between at-planting and first match head square), and N application method (banded or broadcast) for cotton grown in a high-residue rye (Secale cereale L.) conservation system. Lint yield and leaf chlorophyll meter readings were used to evaluate N management practices. Chlorophyll meter readings did not correlate with cotton yields during these growing seasons. Optimal yields were obtained with 134 kg N ha-1 in 2000 and 2001 (875 kg lint ha-1 and 1150 kg lint ha-1) and 179 kg N ha-1 in 2002 (895 kg lint ha-1). Generally, highest yields were obtained when N was applied at-planting (900 kg lint ha-1, 1073 kg lint ha-1, and 969 kg lint ha-1 for 2000, 2001, and 2002, averaged over N rates, sources, and application methods). Urea-ammonium nitrate applications resulted in greater yields when banded, regardless of application timing, while AN was more effective when broadcast applied. Given current prices for UAN and AN, the most efficient and economical practice for cotton grown in high-residue conservation systems on these soils would be to apply 134 kg N ha-1 as UAN in a banded at-planting application.