Reports from multiple sources are indicating that the availability of potassium sulfate (sulfate of potash, 0-0-50) for the upcoming tobacco growing season will be limited. At the current time it is not known what factors have contributed to the fertilizer shortage or how long it will last.

But tobacco producers, fertilizer dealers and crop consultants are being advised to make other arrangements when sourcing or making recommendations for potassium (K) fertilizer applications in tobacco production. 

When considering K sources for tobacco production, chlorine (Cl) content is the primary concern due to the toxic effect it can have on the plant when applied at rates greater than 30 pounds per acre. Chlorine toxicity is a result of excessive chloride (Cl-) accumulation and will result in a decrease in leaf yield and quality as well as very poor smoke flavor. 

Complete tobacco grade fertilizers, such as 6-6-18 and 8-8-24, will contain no more than 2 percent Cl or no more than one-half the total amount of nitrogen when nitrogen is greater than 4 percent. Homogenized fertilizers will typically blend various sources of K to meet crop-based nutritional requirements. 

Additionally, non-homogenized K fertilizers such as sulfate of potash and K-Mag  will contain somewhere between 1 and 2 percent Cl. Ultimately, both fertilizer sources (homogenized and non-homogenized) will not oversupply Cl when used at recommended rates.

Since state law limits chloride levels in tobacco fertilizers, issues with excessive Cl content in fertilizers occur when non-tobacco grade sources are used in substitution for fertilizers formulated for tobacco. 

The most commonly used K fertilizer, worldwide, is muriate of potash (potassium chloride, 0-0-60) because of its high K analysis and relatively low cost. Muriate of potash is not recommended as the sole K source for tobacco production, regardless of tobacco type, due to its high Cl content (45 to 47 percent). 

An example of the problem with using only murate for potassium needs is as follows: 100 pounds of muriate of potash applied per acre will only supply about 50 pounds of K+ but will supply around 46 pounds per acre of Cl-.  The end result of this application is that K is in short supply, while Cl is applied at too high of a rate for tobacco. 

The fertilizer K issue is further compounded when soil fumigants are used to suppress soil borne diseases and nematodes. The two most commonly used soil fumigants in tobacco production (Telone and Chloropicrin) both have active ingredients comprised of chlorine-based compounds.  It is safe to assume that these products will provide 10 to 15 pounds of Cl- per acre when used at recommended rates, which only furthers the need to give serious consideration to fertilizer source. So to be safe apply no more than 30 pounds per acre from the fertilizer.