This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
It is very difficult to give an estimate as to what a crop of Mushrooms should cost to grow, or of what weight a given area should produce. The cost of manure and labour vary so much, and the skill and experience that are applied to the crop differ so greatly, that only a rash man would care to estimate for his neighbour. A few figures are given below, taken from actual experience, but at the best they can only be taken as a rough guide. A crop was grown in a glasshouse 220 ft. long by 40 ft. wide. For this 600 yd. of manure was bought at 1s. 6d. per yard. It was damped out and allowed to stop for three days, and was then turned six times at intervals of two days, and the day after the last turn the bed was made up. After three treadings the bed settled down to 6 in., and was then spawned and cased. The temperature was kept about 74° F. by means of litter.
The actual cost of the bed, which covered 8200 ft. super., was as follows: -
600 yd. manure at 1s. 6d. per yard ...
100 bus. spawn at 2s. 6d. per bushel
Labour • • • •• ••• ... ...
One man at 25s. a week and four men at 21s. were employed. To the total the cost of soil for casing must be added. In this instance 40 yd. were used. The cost of making ridges is slightly higher in proportion. The labour included: making the manure and putting down the bed; digging and screening soil and casing the bed; putting down the necessary posts and boards, and all horse labour. The house produced 5 1/2 tons of mushrooms, but a nearly similar house, put down later, only produced 3 tons, although treated as far as possible in the same way. Probably a fair average for all crops is 3/4 lb. of mushrooms per square foot.
Against the first cost of the manure has to be put the value of the spent bed, which will probably be one-quarter to one-sixth of the original bulk of manure (say 100 to 125 yd. out of 600 yd.), and be worth 1s. to 1s. 6d. per yard, according to locality.
Prices of mushrooms vary very much. The following have been average prices for the past few years: October and November, 1s. to 1s. 3d. per pound; December, 9d. per pound; January, 6d. per pound; February and March, 8d. per pound; April and May, 9d. per pound. Summer prices are very much up and down, owing to the difficulty of getting the mushrooms to market in good condition.
For outdoor Mushroom beds in ridges other expert growers estimate the cost at 6s. to 7s. per yard run, and the yield to be from 6 lb. to 10 lb. per square yard. Thus an outdoor ridge Mushroom bed 100 yd. long would cost about £35, and would require 100 tons of manure and about 18 bus. of spawn. Reckoning a yield of 6 lb. of Mushrooms to the square yard on each side of the ridge, the crop would come to about 1200 lb. - over half a ton. At an average price of 9d. per pound the gross receipts would be £45, leaving a profit of £10. To this should be added £2 or £3 for the spent manure, which can be used in other ways.
To ensure regular returns, good manure must be obtained, the labour on its preparation must not be grudged, and, above all things, economy alone should not be considered when purchasing the spawn. A cake of the latter, on being broken, should be full of tiny grey threads just visible to the eye. If the threads are larger, and look like cotton, the results will not be so good.