Hi
Greetings as we advance rapidly into 2026. Believe it or not, we’re still running just above the 10-year average regarding day degrees. Crop development for the most part is in a sweet spot. While most are continuing to regularly apply in-crop shots of N, which I feel is a positive move, I wish to also touch on Potassium, or K as it's known -“is it okay?!”
In refreshing my knowledge of K, the USA is a great place to start. The current commodity price squeeze on the back of repeated large crops finds K under the spotlight. As most of their cropping system is no-till, pre-planting applications of muriate of potash just don’t seem to make it through to the bottom line. Why is this? Potassium likely finds itself stratified near the surface via dryer conditions, becoming not available as the plant seeks moisture. Corn by example as grain sees little K being removed. However much of the K utilised by the plant is bound up in the stover of the corn stalk. Until this is broken down, often with bio digesters, that’s where K remains. Locally, potassium is barely mobile in our dominant clay alkaline soils and K availability will often be limited where the roots are active. This becomes a greater issue as the soil water holding capacity dries down. K availability and timeliness in dry soil limits mineralisation. While soil tests often suggest an abundance of K, the actual pool of available K as it’s mineralised has limitations. Hence,this is often described as the K paradox.
Why do I mention this? In our modern ways of thinking we do dry our soils down repeatedly between watering cycles. Our options to manage the shortcomings of K are limited. Dry fertiliser is a possible opportunity once logistics are overcome. I see great merit in considering Potassium Sulphate as an option because of its inclusion of Sulphur – S, which seems to have been lost in current practices. Cotton is an oilseed crop, which opens unexplored opportunities in that space for S. The genetic capacity from CSD’s suite of varieties is in the order of 16-18 bales/ha locally. Using Rochester’s chart from 2014 tells us we are removing 47kg/ha of K and 17kg/ha of S via seed and lint. One needs to add to these numbers a percentage of efficiency. Anything we apply prior to planting likely becomes tied up, therefore thinking and expecting K to be there on demand if applied months before, is a false narrative for some of the reasons previously mentioned.
The likely short-term fix, while keeping things balanced, is likely to be foliar applications. We know inside the plant, K is very mobile. Well timed foliar feeding is the quickest way to farm our way through the demand during flowering and into boll fill. So as we’re not second guessing, best practice requires some measuring of K. Sap testing is not practiced locally on a wide scale and requires data sets to be developed, which in time should be explored. Presently, we focus on petiole testing. Between these techniques, somehow we get to decisive outcome where we understand the relationships of what have got in the bank and or the corrective actions to improve our ROI for K. What’s in abundance or is a limiting factor should not just stop at N and or H20.
Here is a bit of a check list to consider regarding foliar applications which in most cases will need to go on via air, if overheads is not your thing, at the correct physiological stages.
- Source and quality of the technical aspects of the chosen liquid product.
- Does it contain any heavy metals.
- Quality of water being used by applicators. Water hardness and pHneed to be well understood, which becomes very critical for it to be effective.
- The plant must be receptive. It must be both transpiring and photosynthesizing.
- Likely the best outcomes will be when applied post any dew on the crop during early mornings.
- Stop spraying once temperatures climb about 28°C. A slight breeze and some humidity goes without saying.
- Droplet size and coverage are important. Again, speak to the manufacturer’s representative.
How much K required will ultimately include or involve considerations around variety, rotation, mineralisation and plant health.
Variety trials and field walks
On a final note, two of the 2025-26 Border River variety trials have some hail damage, unfortunately. The remaining 12 are all in excellent shape. Plans are in place with dates being arranged for visits to a number of these in February and March.
Initially, the first dryland double skip trial / walk through will be at “Boolarwell”, Talwood QLD at 4:00PM QLD time on Thursday 5 February, 2026.
An irrigated variety trial walk will be held at “Tundunna”, Mungindi NSW at 4:00PM NSW time on Thursday 19 February, 2026.
Cotton course
If you feel like either you or your staff would benefit from a little bit of extra cotton knowledge in 2026, then it is worth remembering that the new CRDC Cotton Course will be run by the University of Sydney 10-12th March this year. Currently there is a discount available and there are still places.
Look forward to seeing you there, Colin
