Commercial Humates from Coal and Their Influence on Soil Properties and Initial Plant Development

Properties of three samples of coal-derived commercial humates (CH), produced as organic fertilizers by Lomonosov Moscow State University the same company, were examined. Despite the same origin, the samples possessed different properties even with respect to such basic parameters as content of C, N, and humic acids (HA). Two of the CH samples (CH-1 and CH-2) studied were very similar, but CH-3 differed significantly in having a lower content of C and HA; a higher content of N and FA-fraction; and in the character of molecular-weight distribution. The CH samples with similar properties (CH-1 and CH-2) exhibited different growth-stimulating effects; CH-2 was less effective. The least effective was CH-3 in spite of the highest N content. This brought us to the conclusion that either CH-bound N is unavailable for plants, or the amount and quality of HA are more important for growth-stimulating effects of CH than the total amount of nutrients. High application rates of CH inhibited plant development in spite of the higher nutritional value, which indirectly proves their physiological activity. Other possible reasons of inhibiting action of CH could be toxicity of their high doses, or inactivation of bound to HA nutrients.