27 March 1998

SPREADING BEHIND MOWS DOWN COST

Spreading grass directly

behind the mower is one

route to faster wilting and

improved silage quality.

Peter Hill reports

GRASS silage makers looking to trim costs by reducing labour and machinery inputs are turning to mowers that spread the crop behind them, rather than leaving it in a neat swath.

The idea, simply enough, is to expose more of the crop surface area to wind and sun so moisture can evaporate faster. In favourable conditions, all that is then needed is for the grass to be rowed up ahead of the forage harvester, saving at least one or two tedding passes to bring damp grass to the top of the swath.

The more rapid wilt also cuts the time between mowing and chopping or baling, and makes the prospect of high dry matter silage, with its high intake/low pollution potential, a more practical proposition for the UKs climate.

Much of the impetus for the approach has come from Greenland, the Netherlands-based manufacturer of Vicon and PZ mowers and other grassland equipment. The companys Vicon HPC (High Performance Conditioner) system involves a different method of intensive conditioning or crop treatment that combines with spreading to accelerate moisture loss.

Single process

The system forces grass between a nylon brush roller and a metal vein roller, with grass then spread evenly on to the ground in a single process.

A key factor in its effectiveness, says Raymond Jones of the Institute of Grassland and Environmental Research, Aberystwyth, is that wilting is fastest within the first hour of a crop being cut. After that, the "pores" through which transpiration of water occurs naturally in the growing crop, close up. Wilting becomes slower and less effective.

Spreading the crop allows maximum surface area to be exposed to wind and sun to allow rapid evaporation of water, notes Dr Jones.

Initial trials at IGER, which compared a conventional mower-conditioner and swath tedding approach with an HPC mower, showed higher DM content from the new system within the same eight-hour wilt period.

Last year, in another IGER trial, the Vicon system produced a 13% higher DM after 24 hours than mowing and tedding, with no adverse impact on grass quality.

The trial also addressed concerns about the vulnerability of spread grass to rainfall. Again, the ability of the crop to shed moisture faster – 6.4 units DM/hour compared with 1.1 units – countered this concern and, perhaps against expectations, it was the swathed/ tedded grass that appeared to lose sugar content (perhaps through leaching) rather than the spread material, which showed no such loss.

Existing designs

Other firms have taken up the principles of the technique, but using existing plastic or steel tine conditioner designs and with vanes on the mower hood, rather than Vicons grass-driven spreading roller, to distribute grass over the mown area.

Main advantages, they claim, include simpler construction (the machines are significantly cheaper) and that the spreading vanes can be adjusted to produce a conventional swath where appropriate.

Developing the Extra Dry system for the Pottinger Cat Nova mowers involved fitting an adjustable, multi-ribbed conditioning plate which enables the degree of conditioning achieved to be altered to suit crop type and the weather. Close-spaced V-tine fingers convey the crop from the disc cutterbar to the rear of the machine, scraping the waxy surface of the plant stems as it goes.

Other advantages of the cut-and-spread approach, suggest IMAG, include:

&#8226 Reduced costs through quicker harvesting and less bulk to transport.

&#8226 Reduced leaf-loss from the lack of tedding.

&#8226 Less soil compaction thanks to fewer tractor operations.

Pottinger GB offers five mowers with the Extra Dry conditioning/ spreading system, while Krone distributor Amazone has six Easy-spread machines.

All the Krone models are disc mowers with tine-type conditioning systems. Unlike the steel-hooded model field tested here last year, production versions have aluminium spreading hoods and guide plates to keep weight in check.

Each of the spreading vanes is attached individually by bolts and can be adjusted to one of seven positions, which lets the user configure the design to suit individual needs and crops. Alternatively, by removing the vanes and closing the standard-fit swath boards, mowers with an Easyspread system can lay a conventional swath. &#42

Vicon HPC mower-conditioner encourages rapid wilting to achieve higher dry matter within a practical timescale, claims its manufacturer.

Pottinger Cat Nova mowers equipped with the Extra Dry system, have a multi-ribbed plate beneath the hood to give improved conditioning, and spreading vanes to distribute the cut material evenly across the field.

Krone Easyspread system comprises adjustable vanes for grass spreading, though these can be removed to lay a conventional swath.

Rapid wilt mower conditioners


Model Width Configuration Price (£)

Krone Easyspread

243 2.4m (7ft 10in) rear-mounted 8,100

283 2.8m (9ft 3in) rear-mounted 8,850

283T 2.8m (9ft 3in) trailed 12,500

323T 3.2m (10ft 6in) trailed 13,000

4000T 4m (13ft) trailed 21,775

4000T 4.8m (15ft 9in) trailed 28,000

Pottinger Cat Nova Extra Dry

215ED 2.1m (6ft 10in) rear-mounted 6,990

250ED 2.45m (8ft) rear-mounted 8,090

290ED 2.85m (9ft 4in) rear-mounted 8,790

260TED 2.56m (8ft 4in) trailed 11,990

310TED 3m (9ft 10in) trailed 13,790

Vicon HPC

AM2400HPC 2.4m (7ft 10in) rear-mounted *11,430

FM3000HPC 3m (9ft 10in) front-mounted 15,650

KM3000HPC 3m (9ft 10in) trailed *19,545

*£12,180 and £20,345 with swath board kit.