The Potash Development Association (PDA) has published an overview of the role played by potassium in maximising cereal crop development.
Research has consistently confirmed that the nutrient is needed in such large amounts because it is the major regulator of solution concentrations throughout the plant.
In essence, potash controls cell sap content to maintain the turgor or rigidity of the plant, and also supports the movement of all materials within the plant.
Potassium supply is thus essential for all nutrient uptake by the roots and movement to the leaves for photosynthesis.
The nutrient also plays a key role in the distribution of sugars and proteins made by the green tissue for plant growth and grain fill.
Cereal crop development
According to the PDA, adequate available potash is essential to produce high-quality marketable grain with good specific weight and well-filled grains.
A shortage will result in premature ripening with significantly lower individual grain size and weight, and will also prevent some potential grain sites from developing, thus reducing the number of grains per ear.
Cereals convert natural resources – including water, solar energy, and carbon dioxide – into grain.
With light being one of the most common limitations for crops in the UK and Ireland in most seasons, the more sunlight is intercepted, the higher the yield.
As cereals are annual crops, they are not able to capture sunlight all year. The latest measurement data would suggest that cereal crops have the ability to capture up to 60% of the season-long energy.
However, the current Agricultural and Horticultural Development Board (AHDB) benchmark within the organisation’s ‘Wheat Growth Guide’ is based on a figure of 47% for the amount of season-long energy captured.
While there is some opportunity for improvement early in the season, most of the ‘lost’ solar energy occurs in the run-up to harvest, as crops begin to senesce, or deteriorate.
Canopy senescence
The canopy starts to senesce from June onwards. But the speed of senescence will depend on a variety of factors, including moisture availability.
While there is little that can be done about the weather (unless irrigation is a viable option), one of the variables that can be controlled is the supply of potash to a crop.
The level of potassium available to a crop can have a dramatic impact on the speed of its development from flowering through to ripening.
According to the PDA, measurements taken from three soils with varying levels of potash showed crops that were well supplied with potassium took 29 days longer to fully senesce than crops that were deficient. This represented a 64% increase.
With moisture limitations becoming more likely towards the end of the season, one of the reasons for the big difference in speed of ripening from potassium-deficient crops is likely to be related to the nutrient’s impact on stress, the association said.
The PDA said moisture stress significantly reduces growth and accelerates leaf senescence due to the reduced time to translocate metabolites from leaves to grain, which ultimately affect grain yield and quality.
Delayed leaf senescence can therefore facilitate plants in remobilising nutrients from old senescing leaves to young leaves and the developing grains.
The end result is an increased and more sustainable crop yield, according to the PDA.
