采用低温加热法测定土壤固定态铵的探讨

Determination of Fixed Ammonium in Soils Using Low-Temperature Heating Method

以 Silva-Bremner 法为对照,在不同加酸量、温度和时间条件下,测定了土娄土中的固定态铵含量,确定了低温加热法释放土壤固定态铵的最佳条件。该条件是在敞口的情况下,加入 5 mol·L-1 HF-1mol·L-1 HCl 溶液,在 100℃条件下加热 1.5～2 h。以确定的方法测定了全国 38 种不同类型土壤中的固定态铵。结果表明,低温加热法适合于土壤固定态铵的测定。与 Silva-Bremner 法相比,低温加热法测定的 38 种土壤固定态铵误差在 5%左右;两种方法测定结果无显著差异,测定结果显著相关(r = 0.99)。

For reducing the long period of shaking for the release of the fixed ammonium by Silva-Bremner method, a new procedure was proposed. The new procedure is that the soil is heated at low-temperature after removal of the exchangeable ammonium and organic N. A manurial loessial soil was sampled to study the effect of acid volume, temperature and heating time on the release of the fixed ammonium by Silva-Bremner method for making comparison. Through this study, optimal conditions were determined for using such a method: treating soil with 5 ml of 5 mol·L-1 HF-1 mol·L-1 HCl and heating at 100 ℃ for 1.5~2 h. Thirty eight soil samples were collected all over China to compare the results between the two methods. Results show that the two techniques gave virtually the same results for the 38 soils with a coefficient of 0.99, and the relative errors was within 5% for the low-temperature heating method. No significant difference was found in the results between the two methods as shown by T-test for individual pairs of each soil.