Continuing on with my perusal of the relation of fertility and plant disease out of the excellent “Mineral Nutrition and Plant Disease” by looking at potassium (K) this week. For the record, while I do a lot of reading in this area lately, don't get the impression that this is all I read about! For example I recently finished reading “The Iliad” written by the poet Homer (not in the original Greek though).
There is actually not that much to say about the relationship of potassium and plant disease. The only thing that came out of this chapter that could be relevant to us berry people is that K fertilization has been shown to reduce the severity of vascular wilts in several crop plants caused by Verticillium, but only in situations when it is deficient in the soil. When K is sufficient (something around 200 ppm K and above) in the soil, the disease mitigation benefit of potassium additions is not realized. Too, the effectiveness of the K additions is going to depend on the host plant resistance to the disease, as well as the amount of disease inoculum in the soil.
Bottom line is I'm not seeing a lot for us here. Most of our soils on the Central Coast are close to 200 ppm K or well above (see the link to an excellent survey in the Salinas Valley below), so a benefit in the way of vascular disease resistance through the use of more potassium fertilizer doesn't seem to hold a lot of promise.
//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=6029