Influence of olive mill wastewater derived compost on soybean (Glycine max (L.) Merr.) cultivation.

Lysimeter trials were carried out to evaluate the effects of the distribution of compost, obtained from the stabilization of olive mill wastewaters mixed with lignocellulosic residues, on soybean yield characteristics. Treated in this way the wastewaters proved to be non-phytotoxic. Agronomic characteristics (biomass, nodulation, and production) and microbial aspects (number of rhizobia in the soil) were examined during various cultivation phases. The biological nitrogen fixation activity was also measured during the cultivation cycle by means of the acetylene reduction test. On the whole, the test results indicate that the compost added to the soil had a positive influence on the growth of soybean. The agronomic parameters and the nitrogen fixation measurements showed increases in the compost-treated plots. At full maturity, there was an increase both in the epigeal and in the hypogeal biomass as well as in the number of beans, which was directly proportionate to the compost dose. Moreover, a higher number of nodules and an increase of their weight were observed, along with the nitrogen fixation activity and the number of rhizobia in the soil.