CORESTA Congress, Berlin, 2016, Agronomy/Phytopathology Groups, APPOST 14

Addressing calcium deficiency in flue-cured tobacco

North Carolina State University, Dept. of Crop Science, Raleigh, NC, U.S.A.

With the exception of potassium and nitrogen, calcium (Ca) accumulation by flue-cured tobacco is greater than all other nutrients. Despite such high demand, Ca application is not recommended to well-limed soils. In 2015, Ca deficient tobacco was visually and analytically detected across much of North Carolina. Research efforts to correct Ca deficiency have resulted in little or no level of confirmed success. To evaluate the effect of foliar applied liquid Ca, research was initiated in 2015 at a single field site in the Coastal Plain of North Carolina. Ten percent liquid Ca was applied through a solution volume of 187 L/ha at 5.6, 11.2, and 22.4 kg Ca/ha. The same material was also applied at 11.2, 22.4, 33.6, 44.8, and 56.0 kg Ca/ha through a solution volume of 468 L/ha. An additional treatment of 0 kg Ca/ha was included as a control. All applications were delivered five days after topping. Plant tissue and soil samples were collected prior to topping to establish baseline estimates for Ca availability and plant utilization. Additional tissue samples were collected one and three weeks after treatment. Tobacco yield from upper stalk positions and leaf quality were quantified by following final harvest. Calcium content increased with Ca application rate; however, yield was not increased beyond that in the non-treated control. It is theorized that increased Ca content was a result of Ca crystallizing on the surface of treated leaves. Additionally, significant injury was observed in all Ca treated plots, indicating that the salt indices of the various treatments were too great for tobacco to withstand. Lastly, the cost of the chosen Ca material was prohibitive as material cost per application ranged from 104 to 1,041 USD/ha. Ultimately, producers should utilize Ca reserves within the soil profile and practice early topping to promote suitable root growth for nutrient utilization.