Evaluating the Validity of a Nitrate Quick Test in Different Chinese Soils

Because laboratory tests are expensive and time-consuming and may not be available to farmers,soil nitrate quick tests are uired for optimal nitrogen management strategies in China to increase nitrogen use effciency and to reduce nitrogen losses.A total328 soil samples were collected at different soil depths from 225 sites in China,which covered a wide range of climatic and geographicions,soil types,croplands and soil textures,to evaluate the suitability of a quick reflectometer test method for analysing soil NO₃^--Na wide range of soil NO₃^-concentrations,soil types and cropping systems in China,mainly by comparison of soil NO₃^--N assessed by uick-test method(a reflectometer)and a standard laboratory method,i.e.,high-performance liquid chromatography(HPLC).The lectometer showed excellent agreement with the laboratory HPLC method with regard to soil nitrate contents for all analysed il samples.The linear regression had slopes of 1±0.08 and intercepts of±1.38 mg NO₃^--N L^-1 among different soil types and plands.Compared with the 1:1 lines,the regression analysis for each soil type showed statistically significant but small differences slope;the relative difference between the values measured using the two analytical systems varied from-8%to 6%,and there were differences in intercept except for paddy soil.The reflectometer showed adequate,statistically significant precision in determining il nitrate contents,and it could therefore be directly used instead of the laboratory methods for soil NO₃^--N measurement in China.y Words:dilution,N recommendation,nitrate test strip,reflectometer,soil NO₃^--N