A Soil Fungus Trap

Abstract

THE screened immersion-plate method^1–3 for isolating soil fungi has the disadvantages that the plates are not very simple to make and are not suitable for use in stony ground. In addition, when a pit is dug or a cut is made for insertion of plates, the gas relations of the soil are disturbed and some drying of the exposed surface occurs, and these factors may influence the growth of fungi. A development of the screened immersion plate which appears to show promise in overcoming these disadvantages is described here. Essentially the method involves the removal of a soil core and its replacement by a tubular version of the screened immersion plate within one piece of apparatus. The apparatus consists of a stainless steel rod which fits quite closely into a stainless steel tube. Water agar is contained in a number of holes bored through the rod which oppose the same number of holes bored in the tube. A metal stop on the rod fits into two slots in the tube and ensures alignment of the two sets of holes. The lengths of rod and tube employed, and the arrangement of the metal stop and of the holes are such that, when assembled, the section of rod with the agar-filled holes occupies only half the length of the tube. When the unoccupied half of the tube is pushed into soil a core or plug is cut. When the tube is pushed farther, the core and the soil ahead are compressed farther, and the cored space is then occupied by the section of the tube containing the rod. This enables exposure of the agar to a soil surface, through the apertures in the tube, in much the same manner as in screened immersion plates. The soil surface thus exposed has been little disturbed, and isolation of those fungi capable of growing from soil on to the agar can readily be effected. The compression of the soil involved in the removal of the core occurs beyond the area of soil to be sampled and will have little effect on the growth of fungi.