There is a potential in the southeastern US to harvest winter cover crops from cotton (Gossypium hirsutum L.) fields for biofuels or animal feed use, but this could impact yields and nitrogen (N) fertilizer response. An experiment was established to examine rye (Secale cereale L.) residue management (RM) and N rates on cotton productivity. Three RM treatments (no winter cover crop (NC), residue removed (REM) and residue retained (RET)) and four N rates for cotton were studied. Cotton population, leaf and plant N concentration, cotton biomass and N uptake at first square, and cotton biomass production between first square and cutout were higher for RET, followed by REM and NC. However, leaf N concentration at early bloom and N concentration in the cotton biomass between first square and cutout were higher for NC, followed by REM and RET. Seed cotton yield response to N interacted with year and RM, but yields were greater with RET followed by REM both years. These results indicate that a rye cover crop can be beneficial for cotton, especially during hot and dry years. Long-term studies would be required to completely understand the effect of rye residue harvest on cotton production under conservation tillage. 1. Introduction Nitrogen is the most difficult nutrient to manage when growing cotton. About 5,445,749？ha of the cotton were planted in the USA in 2003 . Applying optimum N rates is necessary to maximize economic yields and minimize the negative impacts that N overapplication can have on the crop and environment . Higher N rates than required can result in excessive vegetative growth which increases the proportion of immature bolls, reduces lint quality and cotton yields, and increases disease and insect damage [3–6]. However, N deficiencies can reduce vegetative and reproductive growth and decrease yields . Many parameters combine to determine the optimum N rates for cotton, such as soil type, location, N application method, tillage system, water availability, use of winter cover crops, and potential yield . Conservation systems for cotton production in the southeastern US have increased in adoption to approximately 50% of the 2.9？million？ha planted in this area . The use of winter cover crops has been well documented as an effective method for improving soil chemical, biological, and physical properties [9, 10]. Among winter crop species, winter cereals like rye can have many benefits because they produce high amounts of biomass, are easy to establish and kill, and provide good ground cover during the winter [8, 11]. However, the
J. S. McConnell, R. E. Glover, E. D. Vories, W. H. Baker, B. S. Frizzell, and F. M. Bourland, “Nitrogen fertilization and plant development of cotton as determined by nodes above white flower,” Journal of Plant Nutrition, vol. 18, no. 5, pp. 1027–1036, 1995.
H. H. Schomberg, R. G. McDaniel, E. Mallard, D. M. Endale, D. S. Fisher, and M. L. Cabrera, “Conservation tillage and cover crop influences on cotton production on a Southeastern U.S. Coastal Plain Soil,” Agronomy Journal, vol. 98, no. 5, pp. 1247–1256, 2006.
S. M. Brown, T. Whitwell, J. T. Touchton, and C. H. Burmester, “Conservation tillage systems for cotton production ( USA),” Soil Science Society of America Journal, vol. 49, no. 5, pp. 1256–1260, 1985.
M. S. Reiter, D. W. Reeves, and C. H. Burmester, “Nitrogen management for cotton in a high-residue cover crop conservation tillage system,” in Making Conservation Tillage Conventional: Building a Future on 25 Years of Research, Proceedings of the 25th Southern Conservation Tillage Conference for Sustainable Agriculture, E. van Santen, Ed., pp. 136–141, Auburn University, Auburn, Ala, USA, 2002.
J. J. Varco, S. R. Spurlock, and O. R. Sanabria-Garro, “Profitability and nitrogen rate optimization associated with winter cover management in no-tillage cotton,” Journal of Production Agriculture, vol. 12, no. 1, pp. 91–95, 1999.
C. C. Mitchell, “Fertility,” in Conservation Tillage Cotton Production Guide—ANR-952, C. D. Monks and M. G. Paterson, Eds., pp. 7–9, Agronomy and Soils Department, Auburn University, Auburn, Ala, USA, 1996.
D. Dinnes, D. Jaynes, T. Kaspar, T. Colvin, C. A. Cambardella, and D. L. Karlen, “Plant-soil-microbe N relationships in high residue management systems,” 2007, http://www.sdnotill.com/Newsletters/Relationships.pdf.
G. Siri-Prieto, D. W. Reeves, and R. L. Raper, “Tillage requirements for integrating winter-annual grazing in cotton production: plant water status and productivity,” Soil Science Society of America Journal, vol. 71, no. 1, pp. 197–205, 2007.
C. E. Clapp, R. R. Allmaras, M. F. Layese, D. R. Linden, and R. H. Dowdy, “Soil organic carbon and 13C abundance as related to tillage, crop residue, and nitrogen fertilization under continuous corn management in Minnesota,” Soil and Tillage Research, vol. 55, no. 3-4, pp. 127–142, 2000.
B. Govaerts, M. Fuentes, M. Mezzalama et al., “Infiltration, soil moisture, root rot and nematode populations after 12 years of different tillage, residue and crop rotation managements,” Soil and Tillage Research, vol. 94, no. 1, pp. 209–219, 2007.
S. S. Malhi, R. Lemke, Z. H. Wang, and B. S. Chhabra, “Tillage, nitrogen and crop residue effects on crop yield, nutrient uptake, soil quality, and greenhouse gas emissions,” Soil and Tillage Research, vol. 90, no. 1-2, pp. 171–183, 2006.
W. W. Wilhelm, J. M. F. Johnson, J. L. Hatfield, W. B. Voorhees, and D. R. Linden, “Crop and soil productivity response to corn residue removal: a literature review,” Agronomy Journal, vol. 96, no. 1, pp. 1–17, 2004.
H. Tsuji, H. Yamamoto, K. Matsuo, and K. Usuki, “The effects of long-term conservation tillage, crop residues and P fertilizer on soil conditions and responses of summer and winter crops on an Andosol in Japan,” Soil and Tillage Research, vol. 89, no. 2, pp. 167–176, 2006.
J. R. Salinas-Garcia, A. D. Báez-González, M. Tiscare？o-López, and E. Rosales-Robles, “Residue removal and tillage interaction effects on soil properties under rain-fed corn production in Central Mexico,” Soil and Tillage Research, vol. 59, no. 1-2, pp. 67–79, 2001.
J. W. Doran, W. W. Wilhelm, and J. F. Power, “Crop residue removal and soil productivity with no-till corn, sorghum, and soybean,” Soil Science Society of America Journal, vol. 48, no. 3, pp. 640–645, 1984.
K. S. Balkcom, J. N. Shaw, D. W. Reeves, C. H. Burmester, and L. M. Curtis, “Irrigated cotton response to tillage systems in the Tennessee Valley,” Journal of Cotton Science, vol. 11, no. 1, pp. 2–11, 2007.
D. J. Boquet, R. L. Hutchinson, and G. A. Breitenbeck, “Long-term tillage, cover crop, and nitrogen rate effects on cotton: yield and fiber properties,” Agronomy Journal, vol. 96, no. 5, pp. 1436–1442, 2004.
D. J. Boquet, E. B. Moser, and G. A. Breitenbeck, “Boll weight and within-plant yield distribution in field-grown cotton given different levels of nitrogen,” Agronomy Journal, vol. 86, no. 1, pp. 20–26, 1994.