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Recovery of Fertilizer Nitrogen Applied to Burley Tobacco

Author:
Charles T. MacKown, Tommy G. Sutton
Source:
Agronomy journal 1997 v.89 no.2 pp. 183-189
ISSN:
0002-1962
Subject:
Nicotiana tabacum, nitrogen fertilizers, measurement, isotope labeling, residual effects, drilling, cover crops, Triticum aestivum, Festuca arundinacea, nutrient uptake, crop yield, application rate, application timing, Kentucky
Abstract:
The high cash value of burley tobacco (Nicotiana tabacum L.) may lead to ineffective excess fertilization Of the crop. The effects of N management on fertilizer N use efficiency by hurley tobacco and recovery of residual fertilizer N by a winter cover crop were determined. Tobacco was grown in 1993 at two locations with 0 to 336 kg N ha⁻¹ broadcast applied before transplanting or 168 kg N ha⁻¹ sidedressed at onset of rapid growth (≈ 5 wk after transplanting). Seasonal recoveries of ¹⁵SN-depleted fertilizer N were determined in aboveground tissues of the tobacco crop. The amount of labeled fertilizer N recovered at harvest (29 to 124 kg N ha⁻¹) increased with increasing amounts of N applied, but fertilizer N use efficiency was constant at 36.6 ± 0.9% for broadcast applications. Sidedress N enhanced labeled fertilizer N recovery (43 to 54% of applied N, depending on location), even though total aboveground dry matter was equal to or 12% less than that of plants grown with the same amount of N applied by broadcast. Recovery of residual labeled fertilizer N in the cover crop ranged from 2 to 7% of applied N and was greatest for the highest amount of N applied. Fertilizer N recoveries estimated by the difference method equaled those of the ¹⁵N method at 5 wk after transplanting. At 13 wk after transplanting, the difference method, particularly for applications of 84 and 168 kg N ha⁻¹, overestimated fertilizer N recoveries relative to the ¹⁵N method, and is unlikely to provide an accurate measure of fertilizer N use by burley tobacco across a wide range of N applications. Reducing the amount of broadcast applied fertilizer to give a 10% decrease in air-cured leaf yield would decrease the unaccounted fertilizer N by 80 to 115 kg N ha⁻¹, depending on location. As compared with broadcast application of fertilizer N before transplanting, drill banding the N at about 5 wk after transplanting would equal or further decrease unaccounted amounts of fertilizer N. Joint contribution of the USDA-ARS and Kentucky Agric. Exp. Stn. Journal no. 96-06-079
Agid:
1464138