When the value of arable crops is low there is a temptation to remove costs to maintain profitability. A common cost-saving is the annual investment in phosphate and potash, sometimes referred to as a ‘P & K holiday’, a strategy not without risks according to Yara’s Country Agronomist, Natalie Wood..
“Such decisions are valid, providing the ‘cut back’ doesn’t expose productivity to higher risks and long term sustainability issues,” says Mrs Wood. “This P & K decision, in many cases, is not reversed when crop values increase and long term soil statistics clearly show how this is negatively affecting our soils and putting future yields at risk.”
A P & K target index of 2 is optimum to maintain soil fertility and provide crops with adequate nutrition. Over the last few years, soil values have fallen considerably:
60% of soils now have a P & K Index below 2
This is a 35% increase over the last 15 years
30% of soils had a P & K index of 0-1 in 2015
This was true of only 18% of soils in 2000
“This shows that the situation is rapidly getting worse,” says Mrs Wood. “If your soils have a P & K index below 2, you need to review your P & K management strategy and address the deficiency now, before you start experiencing consistently disappointing crop yields.”
There are a number of aspects to consider in reviewing your P & K management strategy, depending on its current status:
Benefit from higher returns on investment by optimising the timing of your applications. “This spring (February/March) timing will ensure that P & K applications are made when the crop needs it most,” advises Mrs Wood. “This will typically increase wheat yields by 0.3 t/ha. You can also save costs when including P & K with your first nitrogen application, whilst maintaining the ability to be site specific (or make variable applications ) with the second and third nitrogen timings. ”
For those that have taken holidays, there’s more to consider. What has the impact been on your soils? How and when to reintroduce applications? When is the best time to do it?
You’re missing out on the yield increases associated with spring NPKS applications
If your P & K holiday has detrimentally effected your soil index, there is the risk of dramatic yield penalties as soil fertility is eroded over time.
These issues can be overcome by introducing a spring NPKS strategy, supplying all the crops requirements of phosphate and potash together with nitrogen and sulphur . (e.g. YaraMila ActyvaS). The rates of application can be tailored to meet your objectives:
“If you’re just concerned with in-year crop performance, then applying a minimum amount to address current nutrient demand from your crops would be the best solution.
If you want to safeguard all future harvests then you’ll need a longer term nutrient replenishment strategy.
With soils nearly 100% deficient in sulphur it is essential to include with NPK applications to avoid detrimental effects on crop health, quality and yield losses.” Mrs Wood advises.