Articles
INFLUENCE OF MINERAL AND ORGANIC TREATMENTS IN THE RHIZOSPHERE ON THE GROWTH OF TOMATO PLANTS
Many reports in the literature about the wide range of effects produced by humic acid give rise to expectations about beneficial effects of humic acid on growing conditions in the rhizosphere.
Against this background, humic acid was chosen for investigations from a group of suitable organic preparations (fulvic acid, lactates, etc.). Investigation of a combination of humic acid and highly sorptive materials (bentonite and zeolite) is another interesting aspect.
Experiments were carried out with different humic acid concentrations and quantities, using sodium humate in all cases.
Bentonite and zeolite were mixed with perlite used as substrate.
Tomato test plants were cultured to the 10-/11 leaf stage.
The following general conclusions can be drawn from the test results:
Under certain conditions humic acid may influence the growth and development of tomato plants.
Growth may get either stimulated or inhibited, depending on the concentration used and on the frequency of application.
The degree of humic acid effects depends on the concentration of the nutrient solution.
Growth inhibition was more pronounced at 2 mS . cm-1 salinity than with optimal or supraoptimal EC values (3 mS . cm-1 and 4 mS . cm-1, respectively). Growth response was best in the variant with three humic acid treatments (at the 3-, 6-, and 9-leaf stages).
Addition of bentonite (20 % w/w) to the substrate and one humic acid treatment per week turned out to be a suitable combination.
Due to its high sorptive capacity, it can been assumed that zeolite caused indirect nutrient deficiency along with inhibition of plant growth.