The varying structures and moisture contents of compost and the heavy, wet and greasy casing soils means the question of ruffling or not - and if yes how - is becoming an increasing topic of discussion. The actual results of ruffling rest heavily on the type of machinery used and the method. Treating the casing soil has more influence on the cultivation results than many growers think.

About 75% of Dutch growers who harvest mechanically ruffle. The main reason is to achieve better uniformity and a larger number of pieces in the first and subsequent flushes.

On companies that harvest manually, the numbers who don’t ruffle are larger. The motivation here is often heavier mushrooms and a better spread of the flush. Growers who opt to ruffle state the reasons as better planning for the first day of picking, improved uniformity over the beds and higher production. If extremely heavy and dense casing soil is used, ruffling can reintroduce a lighter and more open structure.

Ruffling machinery

Ruffling machines can cost anywhere between € 3000,- to € 15000,- each. The number of rods on the machine – which can vary from one to three – explains a large part of the difference in the price ticket. There are two types of drive available – fully electric or hydraulically driven machines.

On companies that cut mechanically machines with several rods are quite common. The casing soil on this type of farm must be as even as possible on the upper surface and that in as few actions as possible. Work costs time and time is money! Hydraulically driven ruffling machinery usually has a variably adjustable speed using a control valve. Electric drive features no control, stage control or variably adjustable control if a frequency controller is used.
The ideal machine has variably adjustable speed for motion and rod RPM.

The rods or axles that do the ruffling differ in the number of pins or teeth and the shape of the teeth. The number of teeth with normal bed widths can be anywhere between 32 to 66. The shape may be round, flat and straight or flat and slanted. The configuration all depends on how growers intend to cultivate and harvest the mushrooms. 

Ruffling method

Intensive handling of the casing soil serves to break up the mycelium threads in more places in the casing soil. All these mycelium threads will start vegetative growth again during the recovery period causing an explosive increase in the quantity of mycelium in the casing soil. So even if the amount of mycelium with ruffling is acceptable, over-intensive treatment means excess levels of mycelium will occur in the casing soil. This can lead to more mushrooms in the first flush and make it difficult to maintain moisture levels in the casing soil during later flushes. This has a direct influence on mushroom quality.

The intensity of ruffling depends on the number of times the machinery passes over the beds, how deeply the teeth penetrate the casing soil, the number of teeth, their shape, the speed at which the rod(s) revolve(s) and how quickly the machine moves over the bed. Taken as a whole quite a number of variable factors.

Many rufflers have flat teeth positioned straight or on a slant. Slanted teeth will distribute the soil towards the outer edges of the bed and fill any gaps at the edges during levelling. Straight teeth will only push the clumps of soil ahead. This type of ruffling machine usually has 66 teeth per rod.

Currently many growers want to pick a large percentage of mushrooms with a cap diameter of 55 millimetre. The number of mushrooms in the first flush rapidly becomes too high. Reducing the amount of mycelium in the casing soil is a good method to bring down this figure. By using a rod with around 32 teeth and round teeth instead of flat, a casing soil that has been ruffled more lightly will produce less mycelium with less pinheading in the first flush.

Many growers aiming for larger mushrooms at harvest have already switched to using fewer teeth and prefer the round ones. An obvious trait is that the casing soil retains more structure. Levelling is very difficult. Take this into account at filling. 

Growers who don’t want to change the number of teeth and rods immediately can achieve a similar result by increasing the speed of the machine over the bed and decreasing the RPM of the rod. Try changing the toothed wheels or using a different size. Make sure that the pressure roller also revolves faster, otherwise the upper layer of the casing soil will be smoothed over.

Another variable factor during ruffling is the way the soil is compacted. Firmly compacted casing soil creates less gas exchange and consequently less fruit bodies. If the casing soil structure is not entirely as required, the best method is to ruffle and compact at the same time. Bear in mind that you should still be able to press down the casing soil slightly with your hand. Ruffling machines with lights on the inside give a good idea of what’s happening under the pressure roller.

Anaerobic casing soil

To grow less but heavier mushrooms, many growers now choose heavy casing soil types. Levelling intensively or spraying with a high-pressure sprayer will ‘ close’ the surface of the casing soil (creating an anaerobic environment). This restricts mycelium growth in the casing soil.

With this type of casing soil, ruffling needs a lot of attention. An anaerobic casing soil can be seen as a large, obstructive layer that will hinder gas exchange and cause mycelium development to stagnate, if not carefully ruffled. The structure must be kept open and coarse to limit the final number of mushrooms. When this type of casing soil is levelled try and avoid a smooth, plastered effect at all times, otherwise you will have problems with mycelium not reaching the surface during the recovery period.

Ditch

At ruffling a so-called ditch can also be made in the casing soil. This is a physical separation between the two halves of the bed formed by a shallow ditch running along the middle. The ditch is pressed down harder than the rest of the casing soil so produces fewer or no mushrooms in the first flush.

This acts as a tangible and visible guideline to the centre of the bed for the pickers who will not then pick on the other half. This measure considerably improves picking performance, as the pickers no longer have to ‘guess’ where the middle of the bed is. Nearly all pickers tend to pick over the middle line, which costs time and effort. The ditch is easy to make using a wheel mounted to the ruffling machine which digs the shallow dip as it goes.

Critical eye

In the past ruffling was often considered a standard treatment, nowadays we look at it rather differently. Contemporary growers use a wide range of casing soil types, fewer mushrooms are desirable in the first flush and machinery manufacturers play on this trend by offering a variety of machinery.  It may be worthwhile casting a critical eye over ruffling in general and the type of equipment used in particular on your own company.