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Dr. Khan's talk (based on his research in the US and several other continents) centered on the idea that current common testing is measuring exchangeable K and not available K, and that the recommendations made by agronomic advisors and suppliers often do not take the full scope of chemical interactions between the recommended amendments into account. Overapplication of potassium can reduce nitrogen and calcium uptake in plants and reduce the availability of calcium for rhizobium and other soil microorganisms that increase the water and nutrient holding capacity of soils. Since potassium becomes more bioavailable in the presence of water, these practices can reduce the amount of it taken up by plants, which can then show deficiencies, which are then treated by further applications.

In amending the soil to counter the chemical reactions, growers are also placing mechanical strains on the soil in the form of compaction and tillage. Not only do these have associated costs for the operation, they can add to the soil's challenges retaining water and elements and the plant's challenges accessing each.

My take: I have concerns that some of the industry's "best" tests produce results that don't provide a complete enough picture to be actionable. I think that these incomplete representations of reality in the soil help to fuel the overapplication of fertilizers and fuel hours that cause additional harmful effects to the soil, the water, and the favorable climate in which agriculture developed. The approach advocated in the article seems to presuppose the need for further extractive operations, but I think that a wiser rate of application may reveal that we're overproducing to our detriment.