some sparrow eggs

I’m not promoting a new delicacy, especially since sparrows, once such a common bird in my youth, have for many years been in sharp decline. The relative size of different birds eggs gives a convenient way of discussing how fine or coarse the lumps in the casing layer should end up.

I remember maybe 10 years ago, the well-known, freelance advisor Ray Samp giving a paper on casing and advocating casing lumps should mainly be the size of pigeons’ eggs.

I went along with that concept, but now I think a good proportion of hens’ eggs might be better to aim at.
What’s the difference and how would you define a casing lump?

A ‘lump’ is a bit of peat in the casing layer, not necessarily egg shaped, but sufficiently wet and solid that the mushroom mycelium grows around rather than through it.

Such lumps provide the main reservoir of water. It is vital to get the relative amount of such a reservoir, as opposed to quantity of mushroom mycelium, correct. Too much mushroom mycelium in the casing layer is a source of wasted yield. It means there is less mycelium available to form mushrooms.

The casing layer mushroom mycelium is the water absorbing root system for the mushroom. It is going to take up water from the casing layer and this will add weight to the crop.

However if it takes up water too easily the crop could be ‘soggy’.
If you were growing tomatoes, a huge root system would be produced at the expense of weight of fruit. There is a certain quantity of available nutrient available in compost and it should not be wasted producing excess casing mycelium.

Anyway, too much casing mycelium will irreversibly dry the casing out, so that after a ‘soggy’ first flush, subsequent flushes will be ‘light’ due to shortage of water.

Another danger with too much mushroom mycelium in the casing layer is that it will tend to initiate too many pins, or the mycelium will matt and produce no pins at all.

The concept of adjusting the number and size of casing lumps is important, because the size of these can be used to adjust the amount of mycelium in the casing layer.

It is a platitude to write, efficiency in production is now vital for survival. The main expense in producing mushrooms is the compost. Regularly, getting that extra 10% of yield, of high quality mushrooms could make all the difference between profit and loss, survival, or having to quit.

So, is it better to have sparrows’ eggs, pigeons’ eggs or hens’ eggs?

Having all sparrows’ eggs would mean a very large surface area available for the mycelium to grow through. It could eventually mean far too many pins, resulting in small mushrooms, too close together, with picking problems etc.

Having all hens’ eggs could mean too many large air spaces, so that applied water ran straight through. A compromise is required. A proportion of slightly flattened out hens’ eggs on the casing surface are required to spread the pins out.

In between the hens’ eggs should be fine particles and these should be packed tightly enough so that they retain applied water by capillary action. The mushroom mycelium only needs the tiniest pores to get up to the surface.

Paddy McArdle once told me: "Mushroom yield is one-third compost, one-third casing, one-third grower and a wee bit of luck"!
I am constantly amazed to see the range of yields that different growers get from the same compost, so I am forced to agree! As mushroom compost quality fluctuates, one can see average yields fluctuating in tune.

However, the individual yields still show almost as big a range on poor compost, as they do on good compost.

Controlled experiments, using a single batch of compost, but contrasting casing materials, give big differences in yield. For example, if peat is compared with soil, or sand, or rotted down and pasteurised spent compost, peat comes well out on top.

Pure ‘brown’ peat sometimes gives a better yield than ‘black’ peat. But, the latter more than makes up for the difference by producing better quality. Assuming everyone now uses ‘black’ peat, why does one ‘black’ peat casing appear to give a better result than another?

Having worked for over a year with a casing producer, trying to ensure consistent quality, I believe it is the moisture content and particularly the initial structure that the casing layer assumes on the compost that is of prime importance.

The concept of hens’ eggs or sparrows’ eggs is not as trivial, as it might seem. At the moment, a grower may know instinctively, or from experience, what a well-cased house should look like.

The feeling is there, if this compost is good, this should be a high yielding house. But, how to achieve that ideal house?

Most growers employ a couple of men, or a gang, to apply the casing. The men tip a heaped bucket onto each bag, or so many buckets per square metre of blocks and then ruffle through with their fingers to level off.

The drier the casing, the easier their job is, so naturally a ‘dry’ casing is what they prefer to work with.

The problem with casing is that it only requires one or two percent excess water to make it sloppy and difficult to handle, one or two percent shortage of moisture to make the casing brittle and liable to fracture into sparrows’ eggs.

If the casing layer is not going to be ruffled again, to ‘correct’ its structure, it is vitally important to get that structure right, first go. Adding extra water after the casing layer is formed is not going to change sparrows’ eggs to hens’ eggs.

It is up to a grower to let the casing supplier know, when casing is too wet, or too dry and equally important when it is just right. The casing supplier needs feedback.

However, should the casing arrive too ‘dry’, it is up to the grower to show the ‘gang’ what he wants. It is still just about possible to ‘squeeze’ sparrows’ eggs to ‘transform’ them into hens’ eggs and to ‘compress’ the surface of a dry casing somewhat, to help ‘correct’ its overly loose, open structure.

One of the possible reasons why shelf growers consistently get better yields and quality than bag or block growers is because they order sloppy wet casing and then ruffle it on the bed. The machine used gives the casing layer an ‘optimum’ structure. The ‘gang’ has to be regarded as the bag and block growers’ ‘ruffling machine’ and ‘adjusted’ where possible!

A couple of paragraphs on two related subjects seem appropriate.

It is important to check the degree of wetness of the casing after each watering. Just looking at it is not sufficient. A handful of casing should be lifted here and there and squeezed.
This is necessary because it is not good practice to put on the same amount of water, no matter if the casing comes in relatively wet, or relatively dry. If the casing is dry it will need a little more water and if it is wet it will need a little less. It is very important to avoid wet, anaerobic patches forming under the casing, due to over watering.

I am sorry to say I have seen several cases of overlay, or near overlay, just at a time when mushroom prices were ‘good’ for a change.

The grower had either let the mycelium come up too high before trying to stop it, or had not realised the warm conditions of the warm spell were just too much for the cooling system to counteract.

Starting the break half a day or even a day earlier and regularly checking that cooling of the compost is actually slowly dropping to follow the desired curve is very well rewarded.