The yield of Gyromitra esculenta (Pers.) Fr. was surveyed during 1973–82 in a Norway spruce (Picea abies (L.) H. Karst.) dominated stand in Central Finland. The soil surface was treated with different light methods, mainly removing the vegetation and humus layer.
It was shown that is possible to improve the natural yield of G. esculenta by breaking the soil surface. In the 286 m2 of treated the yield could be improved over 50 fold compared to the control area. In the untreated control area, the yield per hectare was 0.98 kg/yr. In treated plots the yield was 52.4 kg/yr (in the best year 191 kg/ha/yr). Fruit bodies of G. esculenta were found in treated plots every year after the soil treatment. The yield was at its best in the two first years declining later to the level of 10–20% of the first year’s yield.
The best natural yield was reached in the last year. The previous year’s precipitation was an important factor influencing the yield of the mushroom.
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