Effect of biochar on nitrogen retention in soil under corn plant inoculated with arbuscular mycorrhizal fungi

Maintaining the levels of nitrogen in agricultural fields to ensure crop yield performance is challenging due to the complex dynamics of nitrogen transformation in soil. Nitrogen is mainly taken up by plant roots in the form of nitrate, but it is considered as an environmental pollutant that threatens human and animal health. Therefore, it is necessary to use adsorbent compounds to retain nitrate in the soil. The effectiveness of two types of biochar produced from rice husk (Br) and populous wood (Bp) and two arbuscular mycorrhizal fungi, namely Funneliformis intraradices (Mi) and Funneliformis versiforme (Mv), on nitrate leaching in soil was evaluated. The soil columns planted with corn were filled with an artificial sandy clay loam soil fertigated with urea fertilizer under glasshouse conditions . After nine weeks of growing the plants, a pulse of nitrogen (0.48 g urea per core) was added to the columns. One week after the addition of urea, the shoots of the plants were removed, and the columns immediately flushed with 500 ml of deionized water to leach the soil nitrogen from the columns. The results showed that the shoots' dry-weight increased significantly (p≤ 0.05) in almost all the treatments with the highest in the BrMi treatment when compared to the control (C). The nitrate concentration in the leachate decreased 79% (from 23.2 mg/l in C treatment to 4.2 mg/l in Bp treatment), but the nitrate concentration in the soil solution increased up to 6.7-fold (Bp was the highest), which suggested a high N retention by the biochars used. It was concluded that the application of biochar and mycorrhizal fungi could reduce nitrogen loss through this artificial sandy clay loam soil and may have some implications in environment conservation.