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CORESTA Congress, Paris, 2006, AP 10

Changes in flue-cured tobacco fertilization practices in North Carolina

PARKER R.G.; SMITH W.D.; FISHER L.R.
North Carolina State University, Raleigh, NC, USA

Traditionally flue-cured tobacco growers have used blended fertilizers that consisted of N, P, and K in ratios of 1-3-3 to 1-1-3 as a base for their fertilizer program. Historically, sodium nitrate or calcium nitrate is applied one to two weeks later to supply the rest of the nitrogen needed. Years of using base fertilizers with high levels of phosphorous has led to fields with very high residual amounts of phosphorous in the soil. Because of the high amounts of phosphorous already in place growers can now use other fertilizer materials to produce their tobacco crop at a reduced cost. Tests have been conducted in North Carolina since 2003 to determine: methods to reduce phosphorous application while maintaining early season growth, methods for applying potassium, and which sources and rates of nitrogen can a flue-cured producer use while reducing input costs, increasing application efficiency, and maintaining yield and leaf quality. Test results prove that on a high P soil a grower can apply 8 kg/ha of P in the transplant water; increase early season growth, decrease days to flowering, and reduce P inputs from 45 to 8 kg/ha (83%). Tests have evaluated different blends of potassium sources applied by broadcasting prior to transplanting or banding at or just after transplanting. Results from these tests show no difference between methods of potassium application for yield or quality. However, it should be noted that potassium could be leached out of the root zone if broadcast prior to transplanting. Tests have also been conducted to evaluate different sources and rates of nitrogen. By using a liquid nitrogen source such as 30% UAN or a higher analysis granular fertilizer, growers can be more accurate and/or efficient in their application while saving money.