Potassium deficiency in agricultural soils is a largely unrecognized but potentially significant threat to global food security if left unaddressed, finds new research involving researchers at UCL, University of Edinburgh and the UK Center for Ecology & Hydrology.
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.
you have to take into account the article is mostly about extremely deficient areas with insufficient application, not the industrial super powers like china and usa that can afford to dump for maximum economic yield.
I do, and read the source paper linked by another commenter as well. The paper itself refers to ‘plant available K’, which is exchangeable K. That’s the potassium dissolved in the water in the soil at the time of the sample being taken, and is not indicative of the total amount of potassium held in the soil. Chasing results from a bad test is a surefire way to get bad results, like starting life saving measures because someone only took a pulse for the split second in between someone’s heartbeats.
The soils in the deficient regions are not just deficient in bioavailable but also in the forms that would need to be liberated for plant use throughout the growing season. just look at the chemistry of a Brazillian or sub-Saharan Oxisol.
Then the paper missed an opportunity to use better testing methodology and language.
I’ll reword my take below: Countries which are not on these types of soils are overapplying potash to an economic detriment of billions, skewing the market for the amendment. This also means that countries with soils like these have reduced access to the amendment. If growers who have more potassium in their soils stopped wasting a resource they don’t need to apply, then other growers without requisite potassium in their soils could access said resource with lower costs and greater availability. With a less skewed market, it’s possible that we do not need further development of mining and extractive operations to avoid potassium shortages.