Potassium; The big K

In the last few issues we have discussed how nitrogen and phosphorus are important to plant nutrition, so in this issue I thought we should complete the set by looking at potassium.


Potassium (K) is one of the “Big 3” when it comes to plant nutrition, it has a multitude of roles within the plant, including;

  • Respiration regulation to photosynthesis;
  • balancing water pressure within the cells;
  • generally making plants more resistant to weather extremes.

If it sounds like it`s important, you`d be right. So how does it work?

Unlike N and P, potassium tends not to be a large part of the soil organic matter. This is because soil biology has a much lower requirement for K, than for N and P, meaning that as crop residues decompose, much of the K is released back into the soil. This is why crops that don`t leave residues like hay production for example, require much more K as fertiliser that those that do leave a stubble.


Potassium is usually categorised into three parts,

  • soluble (The bit that is readily available to plants),
  • exchangeable (Attached to clay particles),
  • and non exchangeable (Not likely to be available anytime soon).

However your soil test will usually only measure the first two.

As I hinted above, your soils ability to store K depends largely on how much clay it contains. Your soil test will have a measurement called CEC, the higher the number the greater storage capacity it has. This is usually a good thing, but be cautious, some recent thinking is that heavy soils (High CEC) may hold the K too tightly, and not allow it to convert to a soluble form quickly enough to keep up with plant demands. This may actually mean that you need to put more K on heavy soils than light ones, despite the overall quantities being much higher, but I recommend you discuss this with your agronomist.

The other thing to be a bit careful with when choosing you potassium fertiliser is what form it comes in. You will usually be offered a choice between K Sulphate, and K Chloride or Muriate of potash as it`s more commonly known. Muriate is attractive because it is higher in K than sulphate, and it`s cheaper, BUT many plants are sensitive to chlorides and therefore you may unknowingly cause damage. Sulphate on the other hand is certainly more expensive, but is much less likely to hurt your crop.

Either way don`t forget the K!

Reliability and Innovation allow Biloela Grower to aim for Top Yields

Richard Fairley operates a mixed farming operation on the outskirts of the central Queensland farming community of Biloela. Crops grown include Lucerne, pulse grains, and a parcel of organic herbs. These herbs are grown and sold into both the fresh and processing segments of the industry. With these herbs being a high value crop, and also being highly regulated Richard is adamant,

“There is no room here for second guessing what the nutrient requirements of these plants are, nor can we afford to put up with second rate products, we have been using Katek fertilisers for years now and we know what we are getting, and we know they work”.

Chris Dawson, sales agronomist at Ag-N-Vet Moura agrees,

“There is no doubt that Katek has served this industry well, but more important is the constant reviewing of their existing products, and the development of new ones that keeps them on top of the tree. The introduction of their custom blended liquid products is just one example of this”.

As Richard prepares for the upcoming winter crop he knows that every aspect of his farm management skills will be put to the test by everything from weather to governments, but at least he can get some peace of mind knowing his crops nutrient requirements will be in the bag; a Katek bag that is!


Customising an agricultural blend to exactly suit your needs is something we are passionate about. Many blend options are available, including synthetic, organic and mineral inputs in both physical and compound blends.

Customised organic/synthetic blends give you a high performance fertilizer that has all the benefits of an organic base. This combination of microbes, organic matter and plant available minerals is the ideal blend for improving overall soil and plant health.

To give you an idea of what products we have available take a look at our comprehensive PRODUCT GUIDE of organic and organic based fertilisers.

We have a number of stockists throughout Australia.  Visit our WHERE TO BUY page to find a store near you.  If there is currently not a stockist listed for your area give us a call.

Our Sales Manager Andrew Weeks would love to answer any questions you may have about our products and help you choose the right product for your fertiliser program or customise a blend to suit your soil needs.

For more information or to chat about product options, 

give Andrew a call on 0427 223 307.