It should be noted that in the investigations of Persin, the soil adsorbed only those water-soluble organic substances which are obtained from decomposed plant residues, i. e., substances formed by bacterial activity.
(only those water-soluble organic substances; are obtained; from decomposed plant residues, i. e., substances) (substances; formed; by bacterial activity)
only those water-soluble organic substances substances
are obtained formed
from decomposed plant residues, i. e., substances
by bacterial activity