Whether a useful tool for improving soil condition or a source of income, most growers consider straw as a valuable asset. But how can farmers maximise return from this commodity? Abby Kellett and Richard Bradley report.
In light of the many pros and cons associated with the removal and incorporation of straw, Frontier Agriculture is encouraging farmers to undergo an annual decision-making process to identify the best way to use their straw.
Whatever system growers choose, their decision should reflect fertiliser prices, local straw demand, soil organic matter levels and the farm’s management practices, according to Soyl technical manager, Simon Griffin.
He says: “Straw is selling for about £50/tonne – about £10/t more than last year. Providing weather is dry, straw can often be baled immediately after harvest, meaning fields can be cleared in good time for autumn drilling.
“This all sounds appealing, but is it the best option for your farm? Straw contains large amounts of nutrients, particularly P and K. For example, a 10-tonne crop of wheat will typically remove an additional 6kg/hectare of phosphate and 48kg/ha of potash if baled. At today’s fertiliser prices, this will cost £20-£25/ha to replace.”
Oat straw contains even higher levels of potash according to Frontier fertiliser technical development manager, Mike Slater.
He says: “There is a lively oat straw market, particularly for horses, but oat straw contains the highest levels of potash,” he says.
While incorporating straw has beneficial effects on soil organic matter levels long-term, the short-term rise in organic matter is actually small when compared to other methods, such as the spreading of farmyard manure. Therefore, a straw for muck agreement may be more beneficial.
Mr Griffin says: “If a straw for muck agreement is an option, then the amount of P and K in any muck should be calculated as this may well be more than the amount of P and K removed in straw.
“Manures will also increase soil organic matter levels faster than straw incorporation and is therefore a more efficient way of improving organic matter.”
However straw incorporation has been shown to improve the workability of soil, which can lead to fuel savings.
Where no other sources of organic matter are available and where soil organic matter levels are below 5 per cent, Mr Griffin says growers should consider chopping and spreading straw.
Although the spreading of straw has not been found to increase disease or weed incidence, slug populations have doubled in some instances where residue has remained on the soil surface and where slug pressure was already high.
In baling and removing straw, the estimated benefit associated with reduced slug control costs and lower levels of slug damage, is about £20/hectare (£8/acre), says Mr Griffin.
Consideration should also be given to cultivation methods since shallow tillage may leave straw at seed depth and potentially affect subsequent establishment.
In order to minimise this, Mr Slater says any straw which is incorporated should be chopped and spread well, particularly where the crop is large. Financially, there are savings and gains to be made from each approach.
Mr Griffin says: “A farmer who sells straw in the swath at £8-£15/t rather than chopping it for incorporation may expect to save £4-£5/ha from not chopping straw. A farmer who bales, carts and stores his straw will typically achieve a net return of £80-£150/ha.
“The cost of any damage caused by running machinery must also be taken into account. This can be partly alleviated by reducing tyre pressures where possible and by limiting where vehicles can travel.”
Mr Slater warns delays in establishment, particularly with oilseed rape, can lead to substantial yield loss, so timeliness should also be a key consideration.
He says: “Farmers looking to get OSR in the ground, particularly in the North, have a narrow window to do so. If straw cannot be removed quickly, I would revert to chopping and spreading it to avoid delaying establishment of the next crop, which could be financially damaging.”
Since compaction can cost up to £55/ha (£22/acre) to fix using a subsoiler, Mr Griffin says care should be taken to minimise the damage associated with carting bales from the field where growers have opted to bale straw.
Traditionally, bales would be collected using a flat trailer and loader tractor or telehandler, which may make use of available machinery but it might not be the most efficient way of clearing a field and is likely to cause compaction.
This compaction could be multiplied if large bale grabs are used to collect multiple bales at once, putting a large amount of weight on the loader’s front wheels.
One option to reduce potential compaction associated with loader-based systems is to fit balers with an accumulator, which allows large square bales to be strategically dropped at certain points in the field, particularly the headland.
Commonly available in three to five bale capacities, the units trail behind the baler’s chamber, with bales either collected in a vertical stack by a lifting unit, or pushed left and right to create a horizontal row. Once the headland or desired number of bales is reached, the stack can be dropped to the ground from inside the cab.
Along with boosting output, grouping bales with an accumulator should help prevent compaction as trailers can travel along tramlines, with the loader working in close proximity.
Where large stacks at the edge of a field or in a yard are to be created, larger bale chasers are also an option. The towing tractor and chaser straddles tramlines to pick up each bale individually, with two pickup methods commonly used. One style features an offsetting drawbar with bales turned through 90-degrees by a frame mounted to the tractor’s front linkage. Other designs are commonly trailed directly behind the tractor, with a side-mounted grab or loading conveyor used to pick up bales which turns bales before loading onto the trailer.
Capable of carrying up to 16 bales measuring 90cm by 120cm, the chaser tips vertically to create an eight-bale high stack. However, most machines cannot overlap bales to create a stable stack. To produce taller and better secured stacks, telehandlers are required.
Chasers also offer quick clearance, with manufacturers such as Arcusin claiming up to 100 bales can be shifted per hour with its Autostack. But with a price tag of about £60,000, these machines are likely to appeal more to baling contractors and larger farms.