There is growing evidence to confirm the link between soil potash levels and straw strength within cereal crops.
The follow-on impact of this association on subsequent crop lodging will be of concern to growers
According to the Potash Development Association (PDA) this year has seen a significant number of crops in the UK and Ireland lodging due to the heavy rains and strong winds that were such a feature of the summer months.
Whilst plant growth regulator (PGR) programmes may be scrutinised, it is worth considering all the factors that can affect straw strength and crop’s standing ability.
These include disease and crop nutrition. In relation to nutrition, potash enhances the development of strong cell walls and therefore stiffer straw.
Lodging
Lodging is also affected by obvious factors such as variety, nitrogen rate and weather.
But low potash levels also increase the risk of lodged crops with the associated loss of yield and quality. The effect can be as dramatic as a lack of growth regulator.
Potash is clearly not the only factor affecting straw strength and lodging risk, and as already mentioned the weather was particularly suited to lodging this year.
But considering this follows a period of high potash prices and a succession of years of reduced potash applications, not to mention increased offtakes following last year’s high yields, it could be worth giving this input an extra thought this autumn.
Since the mid 1990s, average potash usage in many parts of the UK and Ireland has been less than potash removed in cereal grain and straw.
Soil potash reserves
This has resulted in an inevitable reduction of soil potash reserves. A similar imbalance has developed for some other main arable crops and this also applies to phosphate.
These trends have continued and will lead to serious consequences for yield and quality.
The length of time before financial penalties occur will depend on soil type, manure use and the phosphate and potash reserves of individual fields.
Potash affects both yield and quality of grain as well as the general health and vigour of the plant.
Cereal crops need at least as much, if not more, potash than any other nutrient including nitrogen.
Potash is needed in such large amounts because it is the major regulator of solution concentrations throughout the plant.
It controls cell sap content to maintain the turgor of the plant and supports the movement of all materials within the plant.
Potash supply is thus essential for all nutrient uptake by the roots and movement to the leaves for photosynthesis, and for the distribution of sugars and proteins made by the green tissue for plant growth and grain fill.
Specifically, potash enhances the development of strong cell walls and therefore stiffer straw. Lodging is affected by obvious factors such as variety, nitrogen rate and weather, but low potash levels also increase the risk of lodged crops with the associated loss of yield and quality.