Procedure to extract soil samples under field conditions

Sampling procedure is as follows: The sampler is placed on the soil over the roots of the plant (foliage was removed). The tube is pounded into the ground by several hammer blows on the cap so that only the head of the tube is above the ground surface. Then the cap is removed, and, if necessary, the core is lightly tamped with a compactor. The U-shaped puller jaws are placed beneath the sampler shoulders, and the sampler is raised, usually within 2 minutes. Core loss, particularly in dry or sandy soils, can also be prevented by lightly tamping the upper end of the core with the compactor (diagram, part #9) before lifting the tube. Because large forces accumulate during lifting, particularly in dry soils, the notches on the jaws must fit the protuberances on the shoulders. Lifting the core sampler is relatively easy, often carried out by our less robust technicians (see PowerPoint presentation).

After the soil sampler is removed, the cutting point is unscrewed. Under wet soil conditions this should be carried out with Ridgid chain wrenches. To avoid compressing the soil core, it is advisable not to push the core out of the tube. Rather using a flame-sterile 9-mm wide stainless steel spatula, the soil core is cut through the furrow according to the depth markers and the 50-mm-long segments were sequentially removed through the cutting point into hermetically-closed and marked plastic bags (see PowerPoint presentation).

Precautions and extra activities during samplings

For successful operations, the soil sampler must be clean. Therefore, after each soil core is removed, a long-handled rough brush is used to remove the remaining soil adhering to the tube. Also, soil particles often penetrate the threads of the cutting point during the coring process. If the screw threads are not thoroughly cleaned, a loose fit can form between the tube and the cutting point when the cutting point is screwed back on. This may cause the cutting point to break from the stresses developed when hammer blows drive the sampler into the ground. If the objective is to sample soil microorganisms, before the next sampling, the sampler should be sterilized by alcohol flaming after brushing and rethreading the cutting point.

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