Three indophenol blue methods have been used to analyze ammounium-N in five typical soils in China. Method I and II, using the same catalyst of sodium nitroprusside but different quantity and types of reagents, are suggested by Soil Science Society of America (SSSA) and Soil Science Society of China (SSSC), respectively. Method III adopts acetone as the catalyst. It was shown that three methods yielded similar ammonium-N contents with each type of soil. But the use of sodium nitroprusside resulted in higher experimental sensitivity; and Method II by SSSC was recommended due to its lower cost.

Nitrate is one of the major nitrogen forms absorbed by plants. Dual-wavelength Ultraviolet Spectrophotometry (DUS) is a simple, rapid and environmental method to measure soil nitrate. In this study, DUS as well as Phenol Disulfonic Acid Procedure (PDAP) were adopted to analyze nitrate in five types of soils in China. It was showed that the concentrations of soil nitrate determined by DUS were higher than those by PDAP. Meanwhile, these two series of measurements were significantly correlated. Therefore, the DUS is worthy in rapid detection of soil nitrate.