Mineralization of microalgal carbon and nitrogen in sodic soils

Abstract

Sodic soils pose a challenge for the agricultural production due to their lack of nutrients, poor structure, low organic matter content, and susceptibility to erosion (water and wind). Their recovery is carried out by soil washing and applying calcium salts, which are sometimes unprofitable processes. A low-cost and environmentally friendly alternative to remedy adverse soil conditions is bioremediation using microorganisms or organic amendments. For this reason, this study intended to evaluate the effects of the addition of dry microalgal biomass on sodic soils and suggest its use as an organic amendment. The effect of the microalgal biomass was studied through the mineralization dynamics of carbon and nitrogen sources in short-term experiments. All experiments were performed at laboratory scale. Microalgal biomass was obtained from a consortium grown in dairy wastewater and subsequently dried and pulverized. Four different treatments of dry microalgal biomass were applied to 50 g of sodic soil, and high microbial activity was observed in the soil (obtaining a production of 240 mg C-CO2/kg dry soil), along with the production of nitrates (presenting values 33.8-1.45 mg N-NO3+/kg dry soil) via the release of ammonia (obtaining 5.46 mg N-NH3+/kg dry soil), and mineralization of organic N into ammonium (producing 1071.92 mg N-NH4+/kg dry soil). The microalgal biomass as an organic amendment showed to be prone to mineralization and release of carbon and nitrogen sources, improving the microbial activity in a soil with sodicity problems.