Summary:

Nitrogen is one of the key components of plant production and the nitrogen requirement of the plant supplied either by mineral nitrogen applications or by biological nitrogen fixation. Although the atmosphere contain huge amount of N2, plants are not able to use that as a nitrogen source. Immediately usable forms of nitrogen are nitrate (NO3-) or ammonium (NH4+). The bonds between two nitrogen atoms are quite strong thus, reducing N2 gas to mineral nitrogen forms needs considerable high amount of energy. However, in biological life, microorganisms may convert N2 to mineral nitrogen sources in ambient temperature and pressure; therefore, biological nitrogen fixation is both environmental friendly and sustainable. Industrial nitrogen fixation and mineral fertilization leads both environmental pollution and economic impact. In this research, the effects of humic+fulvic acid (HFA) on nitrogen fixation were evaluated. For this purpose, a pot experiment in controlled environment was carried out. Peanut seeds were sawn in the hole prepared after dual application of HFA doses and rhizobium bacteria. Two times sampling was realized, one in the flowering and the other in harvest time. Results revealed that HFA application was effective on biologic nitrogen fixation; however, increasing HFA doses were adversely influenced determined parameters. Due to the soybean was cultivated as a forecrop at the field where the experimental soil is collected, nodulation was observed even at non-inoculated pots. Nevertheless, the higher values obtained from inoculated plants. Based on the results presented in the paper, HFA was positively effective on a number of parameters evaluated, yet the lower doses should be recommended.