Effect of phosphogypsum addition in the composting process on the physico-chemical proprieties and the microbial diversity of the resulting compost tea.

Phosphoric acid production and olive oil production are among the most important economical sectors in Tunisia. However, they generate huge amounts of wastes (phosphogypsum, olive mill waste water, and olive pomace). In a previous study, we used phosphogypsum (PG), in co-composting with organic wastes. Three composts were produced; their PG content was of 0 (AT), 10 (A10), and 30% (A30). In the present study, we focused on their derived compost teas. The physico-chemical characterization of the different compost teas showed that those from A10 and A30 composts presented higher P and Ca contents than that from control one (AT). The microbial characterization using DGGE showed a noticeable microbial diversity in the different compost teas and that the addition of 10% and 30% PG in the compost had different effects on the compost tea microbial diversity. The identification results showed that the addition of 10 and 30% of PG did not affect the presence of PGPR (plant growth-promoting rhizobacteria) and fungal soil antagonists in the compost teas. Two PGPRs were isolated from AT and A30 compost teas, and their effect on the growth of potato plants in vitro was evaluated.