Margins are extremely tight in the mushroom industry. Mushroom prices have decreased in real terms over the years and virtually all input costs have increased. Growers need to consider any factor, which can allow them to increase their margin. One such measure, which mushroom growers should consider, is the use of mushroom supplement.

Mushroom supplement is used within the industry virtually over the entire world. The Dutch use supplement at what we would consider extremely high rates of 8 to 14 kg per tonne (2.5-4.5% of dry rate).

Dutch growers simply would not contemplate growing a crop with out adding supplement, as they would immediately see poorer performance and returns. Dutch growers quote a possible increase in yield of 15 to 20%.

Similarly in the US supplement use is routinely added at 9-12 kg per tonne (3-4% of dry wt). US growers would expect a yield increase of 10 to 15%.

Ireland is the exception to this trend as supplement traditionally played no role in the Irish industry. This trend is changing however with a small but significant number of growers using supplement.

These growers see the same benefits as their Dutch and American counterparts. Quite simply, if they stop using supplement their yields and margins drop.

One excellent grower who has been using supplement for a number of years feels that he could possibly be getting 30-50 lbs per tonne improvement in yields. This would represent a 7% increase if the grower were previously yielding 550lbs per tonne.

The ‘rule of thumb average’ figures for increase in yields are generally quoted in the range of 5 to 20%. Please note supplement addition rates are much less in Ireland and therefore potential yield increase will also be less (this will be discussed further later).

At this stage it is important to answer the question: What is supplement?

Generally supplement is a protein rich product, which is ‘treated’ in order for it to give up its nutrients right through out the life of the crop. All the supplements on the Irish market are based on treated Soya bean meal. Supplement increases yield and but also improves quality particularly in later flushes.

Supplement can be added at two times: at spawning or at casing in the case of phase 3 (the composter adds it to the compost not the grower in both cases). The results from addition at casing as opposed to spawning are better but this is only possible in the case of phase 3.

Temperatures will increase by 2-4 degrees C during spawn run with supplemented compost. This can be considerably higher when higher rates of supplement are used. The peak in temperature will generally be 48 hours earlier than normal. Supplement encourages more vigorous mycelium growth and spawn run times may be slightly faster. Less heating may (&less oil usage) be required in supplemented crops. Cooling is desirable if you wish to use supplement and is essential if using during the summer period or if using higher rates of supplement. If compost is not totally selective and either Trichoderma or weed moulds are prevalent supplement should not be used. In this instance supplement will feed the moulds and be counter productive. An old saying is sometimes used in connection with supplement: ‘Supplements make good compost better, but it won’t make bad compost good’.

In fact supplement will make bad compost worse! Supplement is added at very low rates in Ireland compared with the rates added above. In Ireland the rate generally added at present is 5 kg per tonne or 1½ % of dry rate. The returns will be less with this lower rate but temperature control will also be somewhat easier.

There is certainly a case for recommending higher rates with experienced growers, growers with good cooling capacity and growers using blocks. Higher rates will require better cooling equipment and more diligent management.

It is important that supplement is added evenly to the compost. This again becomes more critical when using higher rates of supplement.

Supplement has been shown to be particularly affective in brown production and should be also very effective in blocks with the shallower depth of compost and its resultant lower activity.

To consider the economics of supplementation:

If a supplemented crop costs £60 (£3.50 per tonne x 17 tonnes of compost) it requires 120lbs of extra mushrooms to cover the cost of the product (at 50p per lb net of picking).

In other words it takes very little of an increase in yields to cover the cost of supplement! For calculation purposes we will use an example of a grower filling of 17 tonnes and a yielding 550 lbs per tonne.

If this grower increases his yield by 6% by using supplement, this represents 560 lbs of extra mushrooms or £280 (£220 after price of supplement is subtracted). The returns will increase dramatically by using higher rates.

If the higher rate of use results in a 10% increase in yield (using the above example) the returns net of the price of supplement will be in the region of £380 allowing for an extra £30 in the cost of supplement. Again it must be emphasised that a better management regime is required if using higher rates.

I suggest that growers set up the following trial: Growers should commit themselves to using 3 crops with supplement. I suggest that these are filled in the following format: Fill alternative crops with supplement until the 3 crops are filled.

Fill crop with supplement
No supplement
Fill with supplement
No supplement
Fill with supplement
No supplement

This format gives the grower a very good comparison of supplemented crops verses non-supplemented crops.

If using supplement I suggest you use the Amycel Product ProMycel 480. This product is Soya based. It contains 48% protein. Amycel through its supplement division Spawn mate is the world-recognised leader in supplements.

For further details on supplement or the Amycel product ProMycel 480 please contact any Amycel technical personnel.