Machine focus: Massey Ferguson adds science to the art of tedding

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Between the bouts of unsettled weather that have marked June so far, many are eagerly awaiting the opportunity to cut, dry and shelter a crop of hay.

With the weather being so snappy, it’s important to make the most of any clearings that appear, and so it’s worth thinking about managing the grass while it dries.

An academic approach to tedding

This is exactly what Massey Ferguson has done in collaboration with Cornell University in New York State.

In a study that aimed to examine the effects of tedder setting on windrow spread and ground cover, it was found that the rotor speed of a tedder and the forward speed of the tractor can have a significant effect on how the crop is prepared for drying.

Exposing a large portion of the crop to the effects of solar radiation and wind is generally considered to accelerate moisture loss.

Windrow characteristics

Therefore, it is important to achieve the ideal combination of spreading and piling in order to make the most of the heat from the sun and the air movement within the vegetation.

The characteristics of a windrow will affect its drying rate

For this purpose, three characteristics of the wilted windrow were measured, namely the width of the windrow, the degree of soil cover and the height of the wilted windrow.

These were examined in conjunction with two operating parameters, rotor speed (PTO) – 540 rpm or 440 rpm, and forward ground speed – 6.5 km/h or 16 km/ h.

spread width

To achieve the greatest spread width, the optimum combination of rotor speed and ground speed has been found, perhaps surprisingly, to be the slowest rotor (440 rpm) and the fastest ground speed (16.5 km/h).

So is it better to go fast when wilting? Not at all, because setting the PTO to 540 rpm and starting at 16 km/h actually gave the worst result.

Rotor speed, when traveling at 6.5 km/h, was not nearly as critical to spread width, but final width at either rotor setting was still significantly below optimal settings.

ground cover

Making the most of the field surface is obviously an important consideration, and the amount of surface coverage available should be closely related to the spread width, but this is not the case.

Swath tedder tedding grass crops
A wider tedder will maintain work rates at lower speeds, but will cost more

The best way to get optimum surface coverage was found by going slow with the PTO set at 440 rpm.

The effect diminished with increasing speed of both parameters, with the worst result being obtained at fast forward and rotor speeds.

The variation between the two approaches ranged from 85% at best, to 65% ground coverage at worst.

Average wilted swath height

The big winner here was a slow forward speed, actual PTO speed made very little difference.

At 6.5 km/h, the average windrow height was just over 15 cm; at 16km/h it was just under 13cm, a clear difference of 2.5cm between the two.

An average figure, of course, hides any variation and when looking at swath smoothness, the real effect of different operating parameters comes to the fore.

Again, the slower ground speed showed the least variation between PTO speeds, while at 16 km/h the slow rotor speed resulted in a much “lumpier” swath than when the PTO was set at 540 rpm.

It was no small feat either, the difference was more than 5cm between the two PTO speeds at 16 km/h, while at 6.5 km/h the difference was barely noticeable .

A mixed bag from Massey Ferguson

There is little that is clear from these results. Although they indicate the effect on the windrow of changing two of the operating parameters, they do not give a clear picture of the best tedding practices.

To give a more accurate indication of the overall best strategy, we need to know what the effect was on the nutritional value of the stored grass. Unfortunately, the rain disrupted the tests and this decisive data was not recorded.

Despite this lack of conclusive evidence, the current advice to go fast on the first pass and then slow down on subsequent treatments seems sound.

Possible tedding strategies

By wilting at a higher speed, the full width of stubble left by the previous pass is likely to be covered, assuming the mower has been set to leave a guideline for the front wheel to follow.

swath tedder drying
The first pass should spread the swath across the full width of the tedder

After spreading the grass across the width of the cut, additional tedding can focus on crop organization to meet three additional criteria:

  1. Even distribution over the field, best achieved by slow rotor speed and reduced ground speed;
  2. A deep band of uniform density, this density being as low as possible to allow the passage of air. Low ground speed is critical, PTO speed is more or less unimportant;
  3. Loosen individual stems/leaves to prevent lumps and thereby discourage wet spotting. Although not specifically rated, this characteristic is closely associated with low ground speed and PTO, ensuring material is pulled rather than ripped.

Conditioning

Unfortunately, details of the methodology are not given, but it is probably safe to assume that ryegrass turf was conditioned in this test.

Conditioning is usually associated with stem breakage and leaf cuticle breakdown, allowing moisture to escape more easily.

Crop Grass Conditioning
The variables of the conditioning process seem poorly studied

What is not so commonly thought of is that the conditioned grass does not pack as tightly into the windrow, thus reducing the overall density of the windrow throughout the drying period.

Tedding of the cut crop should aim to build on this characteristic of a conditioned windrow; fast traveling in the second and subsequent passes is less likely to do so.

Other questions

This essay is a welcome reminder that there is a science as well as an art to making hay, but there are many other questions that need to be answered.

The relationship between ground speed and rotor speed is complex, with some of the results being compelling.

This suggests that better understanding could lead to more efficient drying and nutrient retention and raises the question of whether tedder design can be improved.

Another major unknown is whether working the crop from different angles will have an effect on drying time.

By cutting through the lines in a windrow, the crop is mixed and it tends to fill in any gaps that are still present, or at least lay the grass on ground that may not have been covered before.

Stubble length will also affect drying time, as longer stubble can aid ventilation while reducing the inclusion of damp, less nutritious stem and lower leaves in the windrow.

Machine development

This is the kind of research that is not as plentiful, or the results as freely available, as would be desirable and Massey Ferguson is to be commended for taking this initiative.

One might well wonder how much attention the company’s engineers are taking results and will we see future tedders with variable speed rotors, or a Tractor Implement Manager (TIM) capability that keeps a tractor forward and PTO speeds at optimum constant?

Windrow management is something that has, until now, escaped the notice of ‘digital with everything’ enthusiasts, and one that may be about to change.

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