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48th TWC, Tob. Work. Conf., 2018, abstr. 09

Evaluation of NCDA&CS boron sufficiency ranges for flue-cured tobacco

JERNIGAN C.H.(1); HARDY D.H.(1); HICKS K.A.(1); McGINNIS M.S.(1); FISHER L.R.(2); VANN M.C.(2)
(1) North Carolina Department of Agriculture and Consumer Services, Raleigh NC USA; (2) North Carolina State University, Raleigh NC USA

Boron (B) is an essential micronutrient for optimum plant growth of flue-cured tobacco and is required in trace amounts (<1.0 lb B/acre). Since use of premium tobacco fertilizer grades that contain trace amounts of B are not typical in today’s production and flue-cured tobacco is not known to be sensitive to B deficiency, B is often not applied. In recent years however, B deficiency in North Carolina has been visually and analytically identified by sampling the most recently mature leaf (MRML). In 2015, 2016, and 2017 research was conducted at five research stations to reevaluate B plant tissue sufficiency ranges using two plant parts (bud and MRML). To assure adequate B sufficiency in transplants, a 1 ppm B concentration in the float bed water was used at all locations. Soil applied treatments of 0, 0.5, 1.0, 2.0, 5.0, and 10.0 lbs B/acre were initiated soon after base fertilizer (8-2-20) application, approximately 2 to 3 weeks after tranplanting. Three foliar treatments were scheduled in 2016 and 2017; 0.25 lbs B/acre at second cultivation followed by 0.25 lbs B/acre at layby, 0.5 lbs B/acre at layby, and 1.0 lbs B/acre at layby. During the growing season, bi-weekly visual ratings were conducted to identify the occurrence of B deficiency and toxicity symptoms. Tissue samples were collected just prior to the two scheduled- foliar applications and at topping. Plots were harvested by stalk position and cured on-station. Yield was quantified and cured leaf was assigned a USDA grade. Crop value was determined through the combination of cured leaf yield and quality. Boron deficiency has not been observed in in any year; however, B toxicity was documented. (Reprinted with permission)