Desert mushrooms

It's often incredible to see that mushroom growing is possible in countries all over the world with, at first sight, totally unsuitable climates! The skill and expertise of growers is really put to the test in circumstances where concerted effort and creativity is required to get good end results. Oman is one of these countries. Gulf Mushroom Products is one of these companies.

By Jos Buth, C point

The Gulf Arab Sultanate of Oman lies on the Gulf of Oman near the mouth of the Persian Gulf. Its breathtaking scenery is still relatively free from mass tourism. Luxurious hotels border sun-drenched, white beaches. Transparently clear seas are home to a wealth of coral, exotic fish and dolphins. Seawater that never drops below a temperature of 28 degrees Celsius. Thermometers can rise to as much as 55 degrees during the summer months, and even in the winters, nighttime values rarely drop below 25 degrees! In Oman they say: ’we have two types of climate, hot and hotter’. It rains maybe once every three years and even then the shower never lasts longer than an hour…..

Gulf Mushroom Products

In this exceptional country, about an hour's drive from the capital Muscat, a modern mushroom growing facility was built by Dalsem in 1999 based on Dutch examples. It's unique in Oman. 

The farm consists of 27 double growing rooms of 400 square metres per room (four shelves per room, six beds high) and 3 phase 2 tunnels with a capacity of 114 tons of compost per week. The tunnels are filled with compost made in the bunkers. The farm has a central chimney and a specially adapted cooling capacity. The mushrooms are harvested manually, mainly as size 35 millimetres.

The produce is sold fresh in the United Arab Emirates and exported preserved in jars to the United States.

Phase 1 and 2

Everything has to be imported into this desert state. The straw comes from Pakistan and is only available chopped. TopTerra, the Netherlands provides the casing soil, while spawn is also imported from the Netherlands. String and iron is removed manually from the straw bales before they are pre-wetted. Two days later chicken manure (from Oman) is added to the straw. The straw is mixed every two days, and via the bunker composting system well decomposed - albeit very short-structured - compost can be filled in phase 2 tunnels.

It's obviously not easy to create optimal phase 1 conditions under such climatic extremes. Much experimentation and know-how has shown how even the smallest details contribute to a good end result. After the phase 2 tunnels have been filled it's remarkable that cooling is needed to bring the compost from the conditioning temperature of 48 degrees Celsius to the ideal 25 degrees for inoculation. The rooms are filled on Saturdays, Mondays and Wednesdays using 95 kilos of compost per square metre, followed by the incubation period. After filling, spawn is sprinkled over the surface of the compost, which is then covered by plastic to prevent dehydration.

Phase 3

Outside air is not used to ventilate during phase 3. The internal cooling system is used to prevent the extremely high outside temperatures influencing cultivation. This means the CO₂ -concentration in the rooms becomes higher than usual.

After an incubation time of 15 days, the rooms are cased on Sundays, Tuesdays and Thursdays. This staggered schedule helps spread the harvesting period and fits well into the nine-week planning.

The casing soil is supplied relatively dry in plastic bales to keep transport costs low. When the bales are opened the casing soil is moistened in a mixing drum, then spread on the compost by a head filling machine.

This method means the structure remains quite fine and airy, even after it has been moistened and during colonization by the mycelium, so the compost is not ruffled. Cooling down in the blow down phase is obviously done internally using pure over CO₂ outside air and no more than strictly necessary to keep the high outside temperatures at bay.

As CACing is not done, harvesting can commence about 20 days after casing.

Casing on different days of the week staggers the various flushes, so the crop can be picked almost every day of the week. Work on Fridays is avoided as much as possible as this is only free day.

Own market

Gulf Mushroom Products trades its own mushrooms. In addition to the fresh market, mainly aimed at the United Arab Emirates, Gulf Mushrooms also operate a preserving factory, which processes mushrooms in jars intended for the American market. The plant can also preserve mushrooms in jars or in cans, but it's currently only worthwhile processing in jars.

Evaluation