CORESTA Congress, Quebec, 2014, Agronomy/Phytopathology Groups, AP 28

Alternative fertilizer rates and programs in the north western Piedmont region of North Carolina

North Carolina State University, Raleigh, NC, U.S.A.

In recent years input costs for macronutrients used in production agriculture have increased significantly. As a result, flue-cured tobacco farmers have been looking for ways to decrease inputs and, ultimately, overall production costs. Research conducted at North Carolina State University has indicated that rates of nitrogen, phosphorus, and potassium can be greatly reduced without affecting yield and quality. Research also indicates that alternative sources for nitrogen and potassium can be utilized without reducing yield or quality.

Flue-cured tobacco producers in the eastern Coastal Plain have been extremely quick in adopting these recommendations. As a result over 50% of the flue-cured tobacco crop receives a portion of total nitrogen from a liquid source (28%, 30%, or 32% Urea Ammonium Nitrate or 21-0-0-24S Ammonium Sulfate). Additionally, nearly 20% of the crop only receives phosphorus fertilizer in a transplant water application. Unfortunately, flue-cured tobacco producers in the Piedmont region of North Carolina have not readily adopted these same practices. As a result, demonstration plots were implemented to educate producers in this specific region.

On-farm evaluations were conducted in 2012-2014 in North Carolina. Nitrogen was applied at three rates: 56, 72 and 95 kg N ha-1 (from 28% UAN) and phosphorus (from 0-46-0) was applied at three rates: 0, 28, and 56 kg P2O5 ha-1. Potassium was applied to each plot at a rate of 84 kg K2O ha-1 (from 0-0-22, K-Mag). All possible combinations of nitrogen and phosphorus rates were used. An additional treatment of 560 kg 8-8-24 ha-1 at transplanting + 11 kg N ha-1, from 15.5-0-0, at layby was included as a conventional check. Plant height at layby, flower emergence prior to topping, and yield/quality/value were unaffected by fertility rate and fertilizer source. Early results demonstrate that reduced nitrogen rates, reduced phosphorus rates, and liquid nitrogen sources are acceptable in this region.