Residual Nitrogen Investigations for Strip-Tilled Flue-Cured Tobacco Production in Virginia.

Flue-cured tobacco (Nicotiana tabacum L.) is an intensively cultivated crop that typically receives four to eight primary tillage passes before being transplanted on a raised row-ridge. Approximately 75% of tobacco production in Virginia is grown in fields classified as highly erodible. Strip-tillage is a conservation tillage system that has been demonstrated to be suitable for tobacco in southern Virginia. Strip-tillage utilizes specialized equipment to cultivate narrow strips into which tobacco is transplanted. Tobacco is typically strip-tilled into the residue of a previous crop or into a specially planted small grain cover crop. This study was conducted to evaluate soil nitrogen levels and nitrogen uptake by tobacco with different strip-tillage cover management programs. The experiment was conducted in 2014 and 2015 at the Virginia Tech Southern Piedmont Agricultural Research and Extension Center near Blackstone, VA on a complex of Durham coarse sandy loam and Worsham sandy loam. Treatments evaluated the topdressing of a wheat cover crop with 22 or 45 kg N/ha. Subsequent fertilization of the tobacco compared the standard N rate (81 kg/ha) to treatments reduced by the corresponding amount of topdressing applied to the wheat. Additional treatments included strip-till following a wheat cover crop with no topdressing and a conventional tillage control. Treatments with a reduced tobacco nitrogen rate had significantly lower petiole nitrate levels than all other treatments throughout the four harvests in 2014. Soil nitrate levels were significantly different on two of the eight sample dates in 2014, but were not consistent. Conventional tillage, 45 N topdress, and no N topdress had higher normalized difference vegetation indices than all other treatments throughout the first three harvests in 2014. Results of this study indicated that the wheat cover crop residue did not adversely affect the uptake of nitrogen by the tobacco crop.