Pre-harvest Potassium for the Sweetest Fruit

Potassium grapes

Yes, Potassium is an essential nutrient for the growth of all plants, ESPECIALLY at maturation for increasing sugars / Brix levels prior to harvest (for juicy, sweeter, tastier fruit!). This harvest-time star is required in plentiful quantity pre-flower also, to improve the total yield (by retaining more flowers and fruit). Potassium also helps ripen fruit faster, so you can harvest earlier. So, it’s no doubt already in your fertiliser regime (or should be!).

What has soil got to do with how well the Potassium works? 

Having healthy soil can really boost Potassium uptake. It’s a holistic approach to achieve optimal fruit quality and plant health.

Let’s get all ‘sciency’: At an atomic level, Potassium has a positive charge; this means it can be classed as a cation. Clay and other organic matter contained in soil, have negatively charged ions. The ability for soil to attract cations is referred to by using the term ‘Cation Exchange Capacity’ or, ‘CEC.’ The higher the CEC of the soil, generally the higher the presence of Cations which include Potassium, and in turn, the better the Potassium uptake of a plant within that soil has.

Other nutrients required by plants that are also classed as cations include Calcium, Magnesium, Hydrogen, Aluminium and Sodium. The levels of these cations can become easily imbalanced and can affect a crops ability to actually absorb Potassium. Potassium is transported through water contained within the soil, so when a crop has a water deficiency, it is very likely to also have Potassium deficiency. For commercial growing, Potassium deficiency is often an issue as plants are unable to source the requirements of the crop from the soil alone, resulting in tasteless produce that is slow to ripen. Foliar adjunctive applications are a necessary addition to modern growing regimes where growers are concerned with growing top quality produce.

For tips on improving your soil health, we have you covered in this article on soil health, and this one on Fulvic Acid. But back to our star, Potassium…

Show me the proof that applying a quality Potassium product makes a difference! 

Many studies have been conducted on the effects that increased Potassium intake has on a plant, particularly crops that are pre-harvest. The results speak for themselves; one of the most notable effects is the increase of natural sugars and acids. (Hello sweet, sweet fruit!)

This is notable because sugar and acid concentrations are regarded as being the most important parameters that affect fruit quality. One study showed that crops treated with Potassium had fruit that possessed increases in the following levels: 

  • 22% increase in Fructose 
  • 35% increase in Sorbitol 
  • 28% increase in Glucose 
  • 105% increase in Malate 
  • 61% increase in Succinic Acid 
  • 112% increase in Shikimic Acid 
  • 59% increase in Citric Acid 

See one of the research articles here.

Another study showed that fruits in crops treated with potassium, matured and ripened two days earlier than those that weren’t treated. Depicting a 16% increase in fruit weight, and a 10 times faster maturation and daily weight gain level, it’s not difficult to see the effects that Potassium has on the growth of fruit. One crop that was treated with a ‘balanced nutrient’ approach, including significant Potassium application, produced a fruit yield that was increased by 23.5%. 

But before you go ahead and buy Potassium in bulk, consider what the Potassium is mixed with first!

The dangers/negatives of applying Potassium products containing Nitrogen or other unwanted fillers.

While you apply Potassium to accelerate the ripening of fruit, beware of what complimentary or bulk filling agents are packaged with the Potassium.

Many Potassium fertilisers and commercial products contain Nitrogen, this is a great option to decrease the cost of your Potassium fertiliser. While Nitrogen is imperative for accelerating the vegetative growth of the plant, applying Nitrogen when not required pre-harvest, can lead to your plants putting all their energy into foliage production and diverting it away from quality fruit ripening parameters; the production of smaller fruit with lower sugars and flavour, that is slower to ripen and with potential post-harvest storage breakdown issues.

So take a good look at that ingredients label, and ask questions of your consultant or supplier to make sure you have accessed the best quality product for your pre-harvest needs.

Many growers have regrettably found that using a cheap product that does not work, can be a very expensive exercise!

So, make sure that when selecting a Potassium product to apply to your crops, you consider the Nitrogen content and other unwanted fillers like Chloride or Sulphate. This will ensure that your fruit yield is productive and that the fruit is of high, saleable quality.   

Want a high-quality Potassium product without Nitrogen fillers? Try K-Forte!

K-Forte is our Potassium product, which contains Phosphorous. It is well known in the wine and fruit industries as being ‘the’ product to apply for bright colours, increased sugar and Brix levels and high quality produce.

K-Forte contains Potassium and Phosphorous, enhancing the size, flavour and sugar content of fruit. It is a fast-acting foliar treatment, is completely free from Nitrogen and combats any deficiencies in record-time. K-Forte powder is also available for soil or fertigation use.