土壤速效氮包括无机的矿物态氮和部分有机物质中易分解的，比较简单的有机态氮。它是NH₄⁺-N，NO₃⁻-N，氨基酸、酰胺、和易水解的蛋白质氮的总和。土壤速效氮含量与有机质含量及质量有关。有机质含量高，熟化程度高、速效氮含量亦高；反之则低。土壤速效氮较能反映近期内土壤氮素的供应状况。 测定原理：在扩散皿中，用碱性溶液水解土壤，使易水解态氮（潜在有效氮）碱解转化为NH₃，NH₃扩散后为硼酸吸收。硼酸吸收液中的NH₃再用标准酸滴定，然后计算土壤中速效氮的含量。
Soil available nitrogen includes inorganic mineral nitrogen and readily decomposable, relatively simple organic nitrogen from organic matter. It is the sum of NH₄⁺-N, NO₃⁻-N, amino acids, amides, and easily hydrolyzable protein nitrogen. The content of soil available nitrogen is related to the content and quality of organic matter. Soils with high organic matter content and a high degree of maturity have higher available nitrogen content; conversely, soils with low organic matter content have lower available nitrogen content. Soil available nitrogen can more accurately reflect the recent nitrogen supply status of the soil. Determination principle: In a diffusion dish, the soil is hydrolyzed with an alkaline solution to convert easily hydrolyzable nitrogen (potentially available nitrogen) into NH₃, which is then absorbed by boric acid after diffusion. The NH₃ in the boric acid absorption solution is titrated with standard acid, and the content of available nitrogen in the soil is calculated.
危险品化学品经营许可证（带存储）