Straw: Fertiliser costs mean tricky choice to chop or bale

• Straw prices higher this harvest

• Ag-inflation has pushed up value

• Valuable phosphate and potash

Growers are being advised to pay special attention to the benefits of incorporating straw this harvest – before deciding whether to bale and sell it off the farm.

Ag-inflation has pushed up straw prices, with many growers looking to take advantage of markets that include power stations, forage and bedding. But higher fertiliser costs mean straw  also has increased value as a nutrient and soil improver.

Growers should consider the value of straw as a cost-effective source of phosphate and potash – and appreciate its importance for soil health and organic matter, says Rob Jewers, a fertiliser and crop nutrition specialist for Hutchinsons.

To make an informed decision on whether to chop or bale, Mr Jewers says the first step is to calculate the value of nutrients removed in baled straw. These can be found in the AHDB Nutrient Management Guide (RB209 Section 4 – Arable Crops). 

“These figures can be used where the straw is not weighed when removed,” explains Mr Jewers, who recommends looking at the values of different straw types using current market data.

Because straw potash content can vary substantially depending on water availability during crop maturity and baling, it is also worthwhile determining the nutrient content of representative straw samples by laboratory analysis.

As an example, a June 2022 price for triple super phosphate of £930/t is equivalent  £2.02p/kg of phosphate, with a muriate of potash prie of £770/t equivalent to £1.28p/kg of potash.

For a winter wheat crop yielding 10t/ha, if the grain and straw is taken off, this equates to 70 kg/ha of phosphate removal in the form of P2O5  and 105kg/ha of potash removal in the form of K2O.

This works out at £64.87 of additional fertiliser value in straw being removed per hectare. In comparison, at last year’s prices this was only £26.07 – which is a difference in value of £38.80/ha.

As another example, removing grain and straw from an 8t/ha winter oat crop removes 77kg of phosphate and 132kg/ha of potash. The fertiliser value of straw removed is £112.86/ha, a difference of £67.68 over last year when the additional value was £45.18.”

Other factors 

“The important message here is that it will be important to reinvest some of the money made back into replacing the nutrition which has been removed,” says Mr Jewers.

“These values are purely the financial replacement value of the nutrients removed in straw only, however there are other factors to be taken into consideration such as increased traffic and soil compaction.

 “Also take into account the timeliness of straw removal and subsequent establishment of the next crop as well as the value of organic matter with regards to building soil structure and water retention.”

Finally, although recent weeks have been extremely dry, Mr Jewers says catchy summer weather means swaths may remain in the field for longer and may even have to be turned if they get wet, generating extra work.