Investigation of azolla compost, azolla biochar and rice husk biochar, on the improvement of some soil chemical properties

Considering the two environmental problems that have plagued the northern provinces of the country in the recent years, they include a high volume of waste after harvesting rice and the excessive growth of azolla fern and the waste after collecting it from the surface waters. This research was carried out in the production of biological conditioners from these wastes and their effect on improving and strengthening the soil edge of the Anzali lagoon. Therefore, biochars have been prepared from azolla fern and rice husk and azolla compost was also prepared as biologicalal conditioners. The effect of these three conditioners on the chemical characteristics of the soil at the edge of the lagoon were investigated. This is the first time that two environmental problems (azolla fern and rice wastes) have been used as an opportunity to improve and strengthen the soils of the region.

For this research, at first, soil samples were taken from the edge of the lagoon. After producing the remedial treatments (rice husk biochar, azolla biochar and azolla compost), they were mixed with the soil sampled from the edge of the lagoon at three levels of 0 (control), 2 and 4% and the treatment was carried out. The samples were incubated in closed incubation containers of 1 kg for a period of six months and the treatments were prepared in 3 repetitions. At the end of the incubation period, the chemical characteristics of the soil including: acidity, electrical conductivity, cation exchange capacity, percentage of organic matter, percentage of organic carbon, and amount of: calcium, magnesium, sodium, potassium, phosphorus, and nitrogen, were measured. This research was conducted as a factorial experiment and in the form of a completely randomized design.

The results of the analysis of variance showed that the effect of the type of biochar and its level, as well as their mutual effect on all the examined characteristics, was significant at the 1% level compared to the control sample. Among the remedial treatments, biochar azolla treatment recorded the best result compared to other remedial treatments with the highest increasing performance on the available phosphorus, nitrogen, sodium, magnesium, organic matter percentage and pH. After that, azolla compost remedial treatment with high increase performance on available potassium, electrical conductivity and cation exchange capacity recorded a better result. The best performance of the modifying treatments was mainly observed at the level of 4 mass percent of the treatment mixed with the soil. By increasing the level of the modifier compound with soil, a significant increase was observed at the level of 5% in all the measured characteristics and elements.

The results of the analysis of variance of the effect of time, biochar type, level of polluted water and level of biochar on all the investigated parameters showed a significant effect at the 1% level compared to the control sample. According to the results of this research, by using biological conditioner such as biochar and compost, it can be seen reducing the amount of agricultural waste and the problems caused by them (depositing, burying and burning them), we can use these problems as an opportunity. Used to modify, strengthen and improve the chemical properties of soils.