Assessing centrifugation technique for obtaining soil solution with respect to leaching of low molecular mass organic acids from pine roots

Centrifugation is a common technique to obtain soil solution. However, this method may disrupt living cells in the soil and release their contents into the soil solution. To examine this possibility, we compared leaching of low molecular mass organic acids (LMMOAs) and dissolved organic carbon (DOC) from the root of Scots pine ( Pinus sylvestris) packed in quartz sand via extraction by centrifugation and milder procedures of water immersion and suction. Centrifugation enhanced leaching of shikimate appreciably; leaching of DOC, lactate, malate, and phosphate was also significantly enhanced. The concentration leached from the root was greater than 10 μM for shikimate, and generally ranged between 0.5 and 5 μM for the other acids. As for actual soil samples, this level of leaching could be appreciably large in upper mineral horizon(s) if the root density is as large as in our experiments and if the concentrations of LMMOAs in the soil matrix are relatively small.