Effect of Herbicide Application on the Production of Shoot and Root Biomass and on the Effectiveness of Biological Nitrogen Fixation in White Sweet Clover (Melilotus Albus Medik.)

Abstract

White sweet clover (Melilotus albus Medik.) is a plant species from the group of legumes, and this is why it has a capacity to fix atmospheric nitrogen on the basis of symbiosis with bacteria of the genus Rhizobium that is not available for most plants.The species is used primarily for the production of biomass and for soil remediation. Biomass of white sweet clover can be used in biogas plants. It is also one of important producers of nectar for pollinators. The aim of the experiment was to find out whether the application of herbicide can influence the effectiveness of biological nitrogen fixation (BNF) in the white sweet clover. The influence of herbicide with active substances bentazone and imazamox in varying concentrations on the production of root and shoot plant biomass and on the concentration of ethylene in root tubercles indicating BNF effectiveness was studied in greenhouse experiments. Tested variants were as follows: V1 � 50 % of recommended rate (RR), V2 -100 % RR, V3 � 200 % RR and control variant without herbicide. Compared with the control, the herbicide reduced the yield of shoot fresh matter (FM) in Variants V1, V2 and V3 by 7.1 %, 24.9 % and 43.7 %, respectively. The decrease was statistically significant in V2 and V3. As to the root biomass, the decrease in FM yield was statistically significant in all three experimental variants as compared with the control. In the yield of dry matter (DM), all variants exhibited decreased DM of both shoot and root biomass, V3 at all times statistically significantly in the shoot biomass and all variants statistically significantly in the root biomass as compared with the control. The concentration of ethylene in samples of root tubercles did not show any significant differences between the control and variants with the applied herbicide. Therefore, there was no demonstrable reduction in the effectiveness of BNF.