HOWARD ET AL.: N FERTILIZATION OF NO-TILL COTTON 157 Soltanpour, P.N., G.W. Johnson, S.M. Workman, J. B. Jones Jr., and Wells, B.R. 1980. Zinc nutrition of rice growing on Arkansas soils. R.O. Miller. 1996. Inductively coupled plasma emission spectrome- Ark. Agric. Exp. Stn Bull. 848. Univ. of Arkansas, Fayetteville, AR. try and inductively coupled plasma-mass-spectroscopy. p. 91–140. Yilmaz, A., H. Ekiz, B. Torun, I. Gultekin, S. Karanlik, S.A. Bagci, In D.L. Sparks (ed.) Methods of soil analysis: III. SSSA Book Ser. and I. Cakmak. 1997. Effect of different zinc application methods 5. SSSA, Madison, WI. on grain yield and zinc concentration in wheat cultivars grown on Thompson, L.F., and N.R. Kasireddy. 1975. Zinc fertilization of rice zinc-deficient calcareous soils. J. Plant Nutr. 20:461–471. by seed coating. Rice J. 78:28–29. Nitrogen Fertilization of No-Till Cotton on Loess-Derived Soils Donald D. Howard,* C. Owen Gwathmey, Michael E. Essington, Roland K. Roberts, and Mike D. Mullen ABSTRACT mature senescence and reduced yields (McConnell et al., 1995). Information on nitrogen (N) fertilization of no-till (NT) cotton Research conducted within the mid-South shows that (Gossypium hirsutum L.) is needed to optimize lint yields and earli- the optimum N rate for cotton production varies with ness. We evaluated five N rates and three application methods for NT cotton production on Loring silt loam (fine-silty, mixed, active, location, soil type, tillage system, winter cover, and ap- thermic Oxyaquic Fragiudalfs) with natural winter annuals as a cover; plication method. On conventionally tilled (CT) Dun- and on Memphis silt loam (fine-silty, mixed, active, thermic Typic dee very fine sandy loam (fine-silty, mixed, active, ther- Hapludalfs) having corn (Zea mays L.) stover as a cover and on mic Typic Endoaqualfs), Ebelhar and Welch (1996) Lexington silt loam (fine-silty, mixed, active, thermic Utlic Hapludalfs) reported optimum yields from banding 50% of the N having winter wheat (Triticum aestivum L.) as a cover. Nitrogen rates at planting followed by banding 50% at pinhead square. of 0, 34, 67, 101, and 134 kg ha -1 were either broadcasted as ammon- Their evaluation included N rates (67–168 kg ha -1 ) and ium nitrate (AN) or injected as urea–ammonium nitrate (UAN) at application timing (at planting and three splits) from planting. Additional treatments included broadcasting 67 kg N ha -1 which they concluded that the 50–50 split application as AN at planting with either 34 or 67 kg N ha -1 banded 6 wk later. of 101 kg N ha -1 resulted in the highest yields. In an Relative to no N, broadcasting 67 kg N ha -1 as AN increased 4-yr average NT lint yields on Loring silt loam from 739 to 1281 kg lint additional study, Ebelhar et al. (1996) showed that in- ha -1 and 2-yr average yields on Lexington silt loam from 1086 to 1535 jecting a 50–50 split (at planting and pinhead) at a higher kg ha -1 . A higher N rate (101 kg N ha -1 ) was needed to increase 2- rate (134 kg N ha -1 ) resulted in maximum cotton yields yr average yields on Memphis silt loam from 821 to 1169 kg ha -1 . on CT Bosket very fine sandy loam (fine-silty, mixed, Broadcasting AN was a satisfactory placement method producing active, thermic Typic Hapludalfs) and Dubbs silt loam yields equal to or higher than injecting UAN or splitting AN for (fine-silty, mixed, active, thermic Typic Hapludalfs). In NT cotton produced on these loessial soils despite different covers Mississippi, Thompson and Varco (1996) reported that and residues. broadcasting 121 kg N ha -1 as ammonium nitrate (AN) and injecting 110 kg N ha -1 as urea–ammonium nitrate (UAN) produced maximum NT cotton yields on Mari- N itrogen (N) fertilization affects yield, maturity, and etta fine sandy loam (fine-loamy, siliceous, active, ther- lint quality of cotton. Evaluating N rates, sources, mic Fluvaquentic Eutrudepts). Hutchinson et al. (1995) and application timing for optimum lint production has reported the need for a higher N rate for both CT and been a major research emphasis within the cotton pro- NT cotton production on Gigger silt loam (fine-silty, ducing states. For cotton, applying an optimum N rate mixed, active, thermic Typic Fragiudalfs) having a win- is essential and may differ within the production areas ter wheat cover. Their research indicated that NT yields due to climatic or soil differences. An optimum N rate were increased with injected N up to 78 kg ha -1 when should maximize yields, while excessive or inadequate native winter vegetation was the cover, while yields were N applications may reduce cotton yields (Maples and increased with N rates up to 118 kg ha -1 with winter Keogh, 1971). High N fertilization may produce exces- wheat. sive vegetation that delays maturity and harvest, and In Tennessee, cotton yields were maximized at lower these conditions may reduce yields and lint quality dur- N rates than were reported for surrounding states. Yield ing years of early frost or prolonged fall rain (Hutchin- response to N fertilization by CT cotton on well-drained son et al., 1995; McConnell et al., 1995). Crop maturity is loessial upland soils ranged from 34 kg N ha -1 (Overton a critical production consideration for cotton producers and Long, 1969) to 67 kg N ha -1 (Howard and Hos- along the northern edge of the U.S. Cotton Belt (Gwath- kinson, 1986). From a review of Tennessee research, mey and Howard, 1998). Nitrogen deficiency causes pre- Howard and Hoskinson (1990) reported that CT cotton yield responses to N fertilization varied with soil and physiographic position. The current N recommendation D.D. Howard and C.O. Gwathmey, Plant and Soil Sciences Dep., Univ. of Tennessee, West Tennessee Exp. Stn., Jackson, TN 38301; for Tennessee cotton production, regardless of tillage, M.E. Essington and M.D. Mullen, Plant and Soil Sciences Dep., Univ. is to apply 34 to 67 kg N ha -1 to alluvial soils and 67 of Tennessee, P.O. Box 1071, Knoxville, TN 37901-1071; and R.K. to 90 kg N ha -1 for upland soils (Univ. of Tennessee, Roberts, Agric. Economics and Rural Sociology Dep., Univ. of Ten- 2000). These ranges allow the producer to select an nessee, P.O. Box 1071, Knoxville, TN 37901-1071. Received 26 Jan. 2000. *Corresponding author (dhoward2@utk.edu). Abbreviations: AN, ammonium nitrate; UAN, urea–ammonium ni- trate; DD60, degree days 60; NT, no-tillage; CT, conventional-tillage. Published in Agron. J. 93:157–163 (2001).