[Effect of Biochar on Ammonia Volatilization in Saline-Alkali Soil]

In order to investigate the effect of biochar on NH₃ volatilization in saline-alkali soils of the Yellow River Delta, continuous laboratory incubation was conducted. Firstly, the recovery rate of NH₃ volatilization by an improved aeration method was determined, the effects of fertilizer particles and aqueous fertilizer solution on NH₃ volatilization were then compared. Finally, the effects of biochar species, application amount, and fertilizer type on NH₃ volatilization rate and total amount were explored. The results showed that the average recovery rate of NH₃ reached 100.30% using ammonium sulfate as the nitrogen source. With the same rate of nitrogen application, the volatilization of NH₃ decreased by 60.29% in the treatment with urea as the aqueous solution compared to the treatment with urea particles, and decreased by 61.40% in the treatment with an ammonium sulfate aqueous solution compared to the treatment with ammonium sulfate particles. Compared with the control treatment (without the addition of biochar and with the addition of ammonium sulfate solution), the addition of 0.5% biochar derived from 300℃ rice biochar (RB-300), 600℃ rice biochar (RB-600), 300℃ cotton biochar (CB-300), and 600℃ cotton biochar (CB-600) reduced the total volatilization of NH₃ by 18.68%, 16.16%, 9.35%, and 8.26% respectively. The volatilization rate of NH₃ was at its highest within two days of fertilization, which accounted for 53.80%-64.02% of the total volatilization. After the addition of the biochar, volatilization of NH₃ decreased at first and then increased in proportion to an increase in biochar content. Therefore, adding a small amount of biochar before field fertilization, combined with the integrated management of water and fertilizer, can effectively reduce NH₃ volatilization and improve nitrogen use efficiency.