Year: 1999
Type: article
Abstract: 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.
Source: Agronomy Journal
Language: English
Subfield: Soil Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: hybrid
Estimated APC paid: $1,800
Funder: University of Kentucky
OpenAlex ID: W2088387879