Farmers baling straw this summer are reminded to tailor nutrient plans for the following crop to compensate for the removal of phosphate and potash.

It is recorded by the AHDB that a 10t/ha wheat crop removes 5kg/ha of phosphate and 50kg/ha of potash in straw.

For an 8t/ha winter barley crop, this is the equivalent to removing 4kg/ha of phosphate and 40kg/ha of potash.

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With grain prices at low levels, growers are turning to baling straw as an alternative income source.

Particularly as wheat and barley straw prices remain firm, with easy market access.

As well as additional income, baling straw brings agronomy benefits such as aiding with direct drilling, reducing slug pressure and the immobilisation of nitrogen where straw residues build up.

However, Hutchinsons fertiliser and crop nutrition specialist Rob Jewers explains that such benefits must be weighed against other factors.

For instance, the compaction risk to the soil from increased traffic, the time impact that straw removal will have on establishing the following crop and the loss of organic matter on soil health and structure.

Rob notes that the potash content of straw can vary substantially depending on the amount of water availability during crop maturing and straw baling.

“It can, therefore, be worthwhile to determine the nutrient content of a representative straw sample by laboratory analysis,” he says.

If growers do decide to bale, Rob suggests reinvesting some of the money from the straw back into replacing the nutrition removed.

Organic manure application or traditional granular fertilisers are the two common phosphate fertilisers which are best to be applied to seed-beds ahead of or at planting.

Microgranular and liquid placement fertilisers can also be applied in smaller, concentrated quantities, making them a more efficient and cost-effective than traditional fertilisers.

A high-yielding crop can require more than 300kg/ha of potassium throughout its growth cycle, with the main uptake period during late flowering, before much of the potassium is returned to the soil as crops senesce.

To maintain an adequate supply of potassium through the peak uptake period, the soil must have the ability to store and release it throughout the growth period.

Rob explained that a soils cation exchange capacity (CEC) is the most valuable measure to indicate a soil’s potassium storage.

Clay and organic matter content have a significant impact on soil CEC.

“A soil with more than 5% organic matter or clay content will lose little potassium to leaching, compared to a sandy soil with low CEC, which allows potassium to move down the soil profile with excess rainfall,” says Rob

“Soils with low indices and CEC should have potassium applied annually in the spring before peak uptake by the plant.”

It is recommended that an in-depth soil analysis is carried out to fully understand the potash and potassium requirements of your soil.