Many soils in the UK are now regularly showing potash indices of 2 or less according to reports, a situation which could limit yields, particularly in some areas with high yield potential.
The situation is particularly severe on compacted or damaged soils where plants struggle to grow sufficient root mass to take up the nutrient from the soil. “The consequence of compaction is that you could have an index-2 soil where roots can’t expand, so the it performs more like an index 1 or 0 soil,” says Mike Slater of Frontier. He adds that potash plays a vital role in stomata function in plants and is therefore key to maintaining water uptake and plant turgidity.
“If you don’t keep plants turgid, they will not be photosynthesising as well as they can and nitrogen use declines,” he adds. However, some growers have questioned the benefits of applying potash as yield effects are not always obvious. However, sampling of crops by the distributor last year showed that in most cases, the low levels of potash found in plant tissue would have had a limiting effect on yield, although other factors such as high light levels may have hidden some of these effects.