A modified UV spectrophotometry is compared with the phenoldisulfonic acid colorimetry, MgO distillation and FeSO₄-Zn reduction method, and copperized cadmium reduction method in determining NO₃^- concentration in soil extracts of nine different types of soils. In the UV spectrophotometry, the value of correction factors (f) is determined by measuring the absorbance of the soil extract solution in the absence of NO₃^-. The mean value of f is 2.2. Statistically, it is highly correlated between the four methods in determination value, particularly in mineral soils with low organic matter (less than 50 g kg^-1). All results show no significant difference between UV spectrophotometry and phenoldisulfonic acid colorimetry. However, the f value still needs to be readjusted in soils with high organic matter (more than 50 g kg^-1). In general, UV spectrophotometry is simple and rapid, and it can be applied to rapid analysis of large batches of soil samples.