Mushroom Compost
Mushroom Farming in South Africa

Compost forms the basis of mushroom farming. The composition and quality of the compost will affect the quality and yield of the mushroom crop.

©Marinda Louw
Mushroom compost at Boland Mushroom, ready for the pasteurisation room.

It is vital that compost quality should be consistent, however, consistently producing high-quality mushroom compost is challenging and requires skill.

In South Africa, most mushroom farmers produce their own compost. In Europe and other countries, huge and highly specialised facilities make compost specifically for commercial mushroom farmers.

How to Make Compost for Mushrooms

©Marinda Louw
This compost is ready and will now undergo a process of pasteurisation.

Good quality compost is integral to the growing cycle of mushrooms. It has to have the right ingredients and must be treated optimally from the beginning. There are many recipes for compost and composting schedules based on the facilities available on each individual farm. Below is just one example.

In South Africa, compost for mushrooms is made with wheat straw, chicken manure and water. Gypsum is also added to improve the structure, as it buffers the pH and aids the release of ammonia in the compost.

A typical formula is 1 000 kg straw (moisture content 15%), 800 kg broiler chicken litter (moisture 40%, nitrogen 4%) and 85 kg gypsum.

Straw bales are thoroughly wet for five to six days, then broken up and mixed with some of the manure. After compiling into windrows and aerated for a few days, the rest of the manure is added. 

The composting process involves a process of mixing the ingredients, aerating and watering it for the process to begin. (The aeration process prevents anaerobic malodours). As the composting process progresses, the temperature starts to increase and reach up to 70℃.

After approximately three weeks, the compost is pasteurised and during this process, nitrogen is converted into protein which serves as a food source for the mushroom spores to grow on.

When the mushroom compost is ready, it is filled into shelves or bags before being inoculated with mushroom spawn.

Spent Mushroom Compost

After harvest, the growing room is sterilised with steam and the spent compost removed from the farm. Spent mushroom compost is a popular compost for gardening but it is recommended to compost it further in order for unstable organic material to break down. Mushroom compost can add organic matter into the soil to increase water holding capacity and provide material for soil microbes to feed on. This will release nutrients locked up in the compost.

By Marinda Louw