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TOBACCO PRODUCTION

Relationships among Soil Nitrate, Leaf Nitrate, and Leaf Yield of Burley Tobacco

Effects of Nitrogen Management

^a USDA-ARS, Grazinglands Research, 7207 W. Cheyenne St., El Reno, OK, 73036 USA
^b USDA-ARS, Western Cotton Research Lab, Phoenix, AZ 85040-8830 USA
^c Dep. of Agronomy, Univ. of Kentucky, Lexington, KY 40546-0091 USA

cmackown{at}grl.ars.usda.gov

Received for publication August 21, 1998. Burley tobacco (Nicotiana tabacum L.) requires large amounts of fertilizer N to produce high yields of cured leaf with the quality traits demanded by buyers. However, excessive N use produces air-cured leaves with undesirable levels of NO^-₃, is uneconomical, and is environmentally unsound if substantial levels of residual soil NO^-₃ remain following harvest. Effects of N fertilizer on relationships among leaf yield, NO^-₃ concentrations of air-cured leaves, and soil NO^-₃ levels were investigated in 1991 and 1992 at two locations near Lexington, KY. Fertilizer N was broadcast at 0 to 448 kg ha^-1 (56-kg increments) before transplanting or banded at 168 kg ha^-1 about 5 wk after transplanting. Soils were a well-drained Maury silt loam (fine, mixed, mesic Typic Paleudalf) and a moderately well-drained Captina silt loam (fine, silty, siliceous, mesic Typic Fragiudult). Cured leaf yield and lamina NO^-₃ increased with increasing amounts of broadcast fertilizer N. Yield increased 3.7% with banded N, compared with an equivalent amount of broadcast N. Banding N also increased the NO^-₃ level of cured leaf lamina by 37% for bottom leaves and 17% for middle leaves; top leaves were unaffected. Soil mineral N (NH⁺₄ + NO^-₃) was proportional to the amount of broadcast N applied, and NO^-₃ levels in the upper 30 cm of soil declined during the growing season. For predicted maximum leaf yields of 90%, critical soil mineral N values of 46 and 88 mg kg^-1 (for Captina and Maury soils, respectively) were estimated from average mineral N concentrations in the upper 30 cm at 3 and 5 wk after transplanting. Early-season soil NO^-₃ testing to predict the NO^-₃ level of cured leaf lamina was not useful; a nearly twofold difference in lamina NO^-₃ was observed among years when soil NO^-₃ levels were equivalent. At 280 kg N ha^-1, a rate commonly recommended for burley tobacco, as much as 37 mg NO^-₃–N kg^-1 soil was found in the upper 30 cm of soil following harvest. Decreasing the amount of fertilizer N broadcast just before transplanting to 168 kg N ha^-1 caused a 10% reduction in yield, a 37 to 65% decrease in lamina NO^-₃, and about a 60% decrease in residual soil NO^-₃ at harvest. Better N management can reduce both the NO^-₃ level of cured leaves and the amount of residual NO^-₃ following harvest.

This article has been cited by other articles:

				C. T. MacKown, S.J. Crafts-Brandner, and T. G. Sutton Early-Season Plant Nitrate Test for Leaf Yield and Nitrate Concentration of Air-Cured Burley Tobacco Crop Sci., January 1, 2000; 40(1): 165 - 170. [Abstract] [Full Text]