[2] [2] Bowers S, Hanks R. Soil Sci., 1965, 100: 130.

[3] [3] Al-Abbas A, Swain H, Baumgardner M. Soil Sci., 1972, 114: 477.

[4] [4] Krishnan P, Alexander J, Butler B. Soil Sci. Soc. Am. J, 1980, 44: 1282.

[5] [5] Krishnan P, Butler B J, Hummel J. Transactions of the ASAE, 1981, 24(2): 306.

[6] [6] Dalal R, Henry R. Soil Sci. Soc. Am. J., 1986, 50: 120.

[7] [7] Morra M, Hall M, Freeborn L. Soil Sci. Soc. Am. J., 1991, 55: 288.

[8] [8] Ben-Dor E, Banin A. Soil Sci. Soc. Am. J., 1995, 59: 364.

[9] [9] Sudduth K, Hummel J. Transactions of the ASAE, 1993, 36(1): 185.

[10] [10] Reeves E, McCarty G, Meisinger J. Journal of Near Infrared Spectrosc., 1999, 7: 179.

[11] [11] Reeves E, Van Kessel J. Journal of Near Infrared Spectrosc., 1999, 7: 195.

[12] [12] Hummel J, Sudduth K, Hollinger S. Computers and Electronics in Agriculture, 2001, 32: 149.

[19] [19] Shonk J, Gaultney L, Schulze D, et al. Transactions of the ASAE, 1991, 34(5): 1978.

[20] [20] Li M, Sasao A, Shibusawa S, et al. Journal of the Japanese Society of Agricultural Machinery, 2000, 62(3): 111.