Potash fertilizer — is there a problem?
The authors mentioned, without offering much evidence, that potassium sulfate would be a better K source than KCl. There’s nothing wrong with K2SO4 as a K source, but it is considerably more expensive than KCl, and there is no evidence that it’s a better source of K for corn and soybeans than is KCl.
Can we get better at fertilizing with K?
Even though the authors asserted that K fertilization is unnecessary in most Illinois soils, they (rather inconsistently) also suggested that producers do their own on-farm strip trials to see if adding K will increase crop yields. This is not a bad idea, as long as we keep in mind that soil test K levels in the medium or higher ranges – say above 250 lb per acre (125 ppm) usually means low chances of seeing a response.
We can add to this the usual warning that looking at a few strips might lead us to wrong conclusions just by random chance of where the strips are located. But we have proposed a project to organize just such an effort in Illinois under the Nutrient Research & Education Council (NREC), and will be giving further information about this if the proposal is funded.