Agaricus bisporus

The white button, brown button and portobello species — the same organism at different stages. About 90 per cent of South African production.

Casing

The layer applied over the colonised compost to trigger pinning. The most skill-dependent step in a button crop.

Contamination

Crop lost or downgraded to competing organisms such as Trichoderma or bacterial blotch. Falls from 16 per cent to 6 per cent across the plan; cumulative break-even sits at 4.25 per cent.

Cook-out

Steam sterilisation of an emptied room before refilling. Skipping it lets a contaminated crop seed the next one; it costs turnaround days, which is exactly why it gets shortened.

Crop retained

The proportion of grown volume actually sold, after contamination and after product not sold inside shelf life. 79 per cent in Year 1, 89 per cent by Year 5.

Crops per room per year

Completed crops divided by rooms. Rising from 5.4 to 6.7 — a quarter more output from identical capital, achieved entirely through turnaround discipline.

Flush

A wave of fruiting bodies. A button crop is normally picked across two or three flushes of diminishing yield.

Phase III compost

Fully composted, pasteurised and spawn-run substrate delivered ready to fill. Buying it in avoids an odour and effluent burden but places yield’s largest determinant outside the farm’s control.

Pleurotus

The oyster mushroom genus, grown on pasteurised straw and supplement rather than on composted substrate. 80 per cent contribution margin against button’s 57 per cent.

SAMFA

The South African Mushroom Farmers’ Association, established 1989. The route to technical information and benchmarking in a sector where training is scarce.

Section 20 limitation

The South African rule capping the set-off of assessed losses at the higher of R1 million or 80 per cent of taxable income in any year.

Spawn run

The period during which mycelium colonises the substrate before casing and pinning.

Spent mushroom substrate

Used compost after cropping, sold as a soil conditioner because it raises organic matter content. Converts a disposal cost into R282 000 of Year 5 revenue.