Potassium for Ripening, Colour, Sweetness and Full Flavoured Fruit

Have you ever eaten fruit that just has NO flavour and is so tasteless that it leaves you disappointed?

At the ripening stage, plants utilise Potassium to increase sugar levels to sweeten fruit so it is full of flavour and delicious juicy goodness. When a plant is deficient in Potassium it is unable to ripen the fruit properly and the sugar levels don’t mature to give the fruit that mouth-watering full flavour that we expect.
During ripening, Potassium is the most abundant mineral utilised by plants until the fruit is harvested. Often soil tests show that the soil contains large amounts of Potassium (K), however, it is often ‘locked up’ or inaccessible to the plants, therefore the soil can have high K levels but the plants can be deficient. This, in turn, affects the fruit quality.
If the plants are not able to absorb enough Potassium they will struggle to produce the fruit of export quality in terms of full flavours, bright colours, optimum levels of sugar and dry matter.
There are classic signs your crop is K deficient, such as marginal chlorosis of the older plant leaves, however, by the time your crop is symptomatic you would already have yield loss and therefore profit loss also.
This has ramifications for each crop type, for example, bland grapes won’t produce flavourful wine and delayed ripening can mean crops can’t be harvested before rains set in (hello fruit split and botrytis!). For any grower, it’s easy to see how a Potassium deficient crop can severely affect the bottom line.
Ensuring optimum Potassium levels of the plant (not just the soil) is imperative at and during ripening stage till harvest. The next question is, when selecting a foliar potassium product, what is best?


Ensure no Nitrogen is present in your Potassium productEnsure your fertiliser product does not contain Nitrogen, as so many do.
Nitrogen is not required during the lead-up to the harvest period, as it encourages new plant growth. Prior to harvest, we want all the plant energy to go into ripening of fruit rather than new vegetation. Potassium products containing Nitrogen will increase leaf growth resulting in lower fruit quality, also possible fruit softening.
How adding Nitrogen at ripening also negatively affects Calcium utilisation
We know that with increased plant growth comes the requirement for much more Calcium (Ca) to fortify that new growth. Calcium can be a difficult mineral to move to fruit especially via the use of traditional fertiliser. However, Calcium is very important as it is required for fruit wall strength (firmer fruit) and assisting plants to resist pest and disease damage at a time when the sugars are high and weak-walled fruit are most attractive to pests.
Having Calcium diverted to the fruit to build stronger cell walls means the fruit will resist splitting, in turn, reducing crop loss.
So, added Nitrogen in a Potassium product utilised for ripening is a BIG negative and one we hope you are aware of when selecting a product for your crops. Ensure you read the labels, as self-education can save you loads of time and money by ensuring you select the correct product at the correct time.
Unless you have a known nitrogen deficiency, having Nitrogen in your Potassium product is wasteful of resources, and can end up COSTING you way more as it is working against what you are trying to achieve by increasing plant growth instead of ripening fruit.
Potassium Nitrate should or could be utilised earlier in the season (well before ripening) to positively influence yield or applied post harvest if needed, however, if applied close to ripening it has no bearing on yield and can NEGATIVELY affect fruit quality.


What CAN be included in your Potassium product to aid ripening?
Our signature Potassium product has ZERO nitrogen in it. But we do include two other important minerals to improve the uptake of Potassium for plants, to increase sugar/BRIX levels (sweetness and flavour) and even to induce ripening (Getting fruit harvested early before Autumn rains is a proactive method to alleviate loss and fruit rejects ).
Enhancing Brix levels is a very complex subject but at the same time is very simple if you know how to manage it. It has been shown that Brix levels are very much associated with the amount and availability of Phosphorus, Potassium and Magnesium. Phosphorous being the energy needed to transform the carbohydrates (Potassium) into sugars and Magnesium is the element needed as a catalyst for all these reactions to occur (simply put).
Phosphorus and Magnesium are very much associated with the sense that Phosphorous allows the uptake of Magnesium and vice versa, so both of them are synergistic in their behaviour. On the other hand, the relationship between Potassium and Magnesium is antagonistic which necessitate having a balance between all of them for better results, thus that is why leaf and soil testing is required and always helpful in this regard.  
In the past, grape growers were told by their winemakers that they were not allowed to apply Potassium during the ripening phase as it would have negative effects on winemaking. Roots, Shoots & Fruits broke that myth in New Zealand. The problem was the forms of potassium that were available were not suitable, the attached minerals impacted winemaking rather than the potassium itself. This is still relevant and important when choosing your foliar potassium product.
Our product contains Potassium and Phosphorus – Both highly required by plants during this ripening period with NO negative fillers or additives or associated minerals that negatively affect fruit quality
A run-down on our signature Potassium product, K-Forte benefits include:

  • K-Forte brings out the colour, size, flavour and higher Baume levels (sugar content) hence premium quality fruit
  • It contains Humic and Fulvic acid – to assist with nutrient uptake, enhanced leaf chlorophyll and plant health
  • Free from Chlorides, Sodium, Sulphates and Nitrogen (no negative impact on wine, or fruit quality )
  • No negative impact on pH, TA or Polyphenols
  • K-Forte can be fertigated as an option if nets are covering fruit
  • Increases soluble solids
  • Bring forward ripening (so important to have the crop picked early before autumn rains set in, which can drastically affect the quality and in turn payment)
  • Does not cause Russet in apples or other fruit quality issues affecting export
  • No withholding period – K-Forte is safe to use right up to harvest although, from a plant utilisation perspective, applications should not be closer than a week pre-harvest as the plant will not have time to use and convert the minerals into sugar
  • Helps plants to be more hydrated, protecting against drought and alleviating plant wilt
  • Potassium assists with keeping disease levels down
  • Totally soluble, and immediately available (If foliar products are Not 100% soluble then minerals are not able to be utilised by the plant)
  • From a human health perspective fruit and vegetables with higher mineral levels aide in increased mineral density in our food keeping us healthy. Trials show increased levels of beta-carotene, ascorbic acid (vitamin C) aspartic acid,  these are utilised as antioxidants in plants and in humans
  • Increase plant photosynthesis (i.e. healthier plants).

Click here to view K-Forte (liquid form) and K-Forte (powder form).
As always, we are here to answer any crop management or nutrition questions you have, please email Molly and she will reply promptly.