1. Principle: Under acid and alkali conditions, relatively simple organic nitrogen is hydrolyzed into ammonium. Qiulin's acid hydrolysis method has been used for a long time. However, this method has unsatisfactory results for soils lacking organic matter and calcareous soils, and the procedures are also complicated. Cumbersome. Alkaline hydrolysis and diffusion are easy to operate. Reduction, diffusion and absorption are carried out simultaneously. It is suitable for the analysis of a large number of samples and has a certain correlation with the nitrogen requirements of crops. Therefore, it is currently recommended to try this method.
2. Operation steps: Weigh 2.00 grams of air-dried soil (1 mm), place it in the outer chamber of the diffusion dish, and gently rotate the diffusion dish to spread the soil evenly. Take 2 ml of H3BO3 indicator and put it into the inner chamber of the diffusion dish, then expose a slit on the edge of the outer chamber of the diffusion dish, and quickly add 10.0 ml of 1 mol/L NaOH solution (if NO3-N is included, FeSO4 needs to be added during the measurement) .7H2O, and use Ag2SO4 as a catalyst to reduce NO3-N to NO4-N), cover it immediately, fix the ground glass with a rubber band, and then put in 40+-1. C incubator, take it out after 24 hours, carefully open the glass cover, and titrate the absorption solution with 0.005 mol/L 1/2H2SO4. At the same time, a blank test was performed.
