2Roth, G.W. et al. Development of a quick test kit method to measure soil nitrate. Cowanun. Soil Sci. Plant Anal. 1991,22(3) : 191 - 200.
3Schaefer, N.L. Evaluation of a hand held reflectometer for rapid quantitative determination of nitrate. Commun. Soil Sci Plant Anal. 1986, 17: 937-951.
8Roth G W,Beegle D B,Fox R H,et al.Development of a quicktest kit method to measure soil nitrate[J].Commun Soil Sci Plant Anal,1991,22(3-4):191-200.
9Schaefer N L.Evaluation of a hand held reflectometer for rapid quantitative-determination of nitrate[J].Commun Soil Sci Plant Anal,1986,17(9):937-951.
10Bischoff M,Hiar A M,Turco R F.Evaluation of nitrate analysis using test strips:comparison with two analytical laboratory methods[J].Commum Soil Sci Plant Anal,1996,27(15-17):2765-2774.