Tobacco is heavily fertilised with potassium and other nutrients to satisfy its needs in many parts of the world. The tobacco cluster region of Salta and Jujuy in Northwestern Argentina usually applies between 200 to 300 kg/ha of K₂O as sulfate or nitrate throughout the growth cycle. The direct supply and assimilation of potassium (K) to the leaves during its exponential growth stages may improve K content in the leaves, which guarantees a good maturation at drying and combustibility. K may also influence dry matter accumulation directly, resulting in higher leaf yields.

The objective of this work was to confirm previous investigations in several countries concerning the effect of foliar sprays with soluble sulphate of potash (SOP) on the commercial yield and quality of flue-cured Virginia tobacco.

Trials were conducted on Virginia tobacco in collaboration with the Instituto Nacional de Tecnología Agropecuaria (INTA) and Finca Experimental La Posta over a three year period in Perico, Jujuy, Argentina. The control was treated with the normal fertilisation programme consisting of 800 kg/ha of a 13-11-27 NPK and 100 kg/ha of granular SOP. The latter was reduced to 75 kg/ha for parcels that received foliar sprays. Three foliar sprays of SOP were applied (6, 12 or 18 kg/ha/spray in the first year and 3, 6 or 9 kg/ha in consecutive years) as a complementary treatment to base fertilisation.

On several occasions, the parcels treated with foliar sprays of SOP consistently gave more high quality leaves. Results suggest that foliar sprays of SOP as complimentary treatment to the base fertilisation can increase yield of high quality leaves, which offers an economic advantage to the farmer, thus confirming previous results in different cropping conditions. On average, higher yields of first class leaves with foliar sprays of SOP amounted to an additional profit of about US$280 per hectare.