Application of Wavelet Packet Analysis in Estimating Soil Parameters Based on NIR Spectra
ZHENG Li-hua, LI Min-zan*, PAN Luan, SUN Jian-ying, TANG Ning
Key Laboratory of Ministry of Education on Modern Precision Agriculture System Integration Research, China Agricultural University, Beijing 100083, China
Abstract：Using the method of wavelet analysis, the NIR spectra of soil samples were decomposed and reconstructed, and higher precision PLS models were established to estimate soil parameter (TN, SOM). One hundred fifty soil samples were collected from a winter wheat field and the NIR spectra of all samples were measured. Firstly, experiment statistic features were analyzed aiming at all soil samples, and the system clustering was carried out for TN and SOM respectively. Then 50 new TN samples and their corresponding spectra, and 50 new SOM samples and their corresponding spectra were obtained. Secondly, the PLS models were established with these new samples based on their corresponding spectra. The models showed a certain amount of accuracy, but it was still not practical. Therefore, wavelet analysis of NIR spectra was tried. The wavelet packet decomposing by eight-level biorthogonal algorithm was carried out, and 256 nodes were gotten. The lowest approximation signal is corresponding to soil moisture and soil texture spectrum trend. The maximal detail signal is corresponding to the high-frequency turbulence caused by the soil particle size, precision of spectrometer, and other uncertainties. After reconstructing these two nodes and then removed from the original spectra, the characteristic spectra corresponding to each soil parameter were acquired. Finally, the PLS models were established for TN and SOM content respectively: for TN content, the calibration coefficient of the PLS model is 0.960, the validation coefficient is 0.920; and for SOM content, the calibration coefficient of the PLS model is 0.922, and the validation coefficient is 0.883. It was showed that the accuracy of each model was highly improved and the models were able to meet the needs of actual production. The research results conclude that wavelet analysis can eliminate or substantially reduce the factors outside the parameters. It can also remove the obstacles in establishing linear models of soil parameters, and it is feasible and potential method for the real-time estimation of soil parameters.
Key words：Spectral analysis;Soil organic matter;Soil total nitrogen;Wavelet packet analysis;Characteristic spectrum
郑立华，李民赞*,潘娈, 孙建英, 唐宁. 近红外光谱小波分析在土壤参数预测中的应用[J]. 光谱学与光谱分析, 2009, 29(06): 1549-1552.
ZHENG Li-hua, LI Min-zan*, PAN Luan, SUN Jian-ying, TANG Ning . Application of Wavelet Packet Analysis in Estimating Soil Parameters Based on NIR Spectra . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2009, 29(06): 1549-1552.
[1] WANG Mao-hua(汪懋华). Transactions of the Chinese Society of Agricultural Engineering(农业工程学报), 1999, 15(1): 1. [2] Al-Abbas A H, Swain P H, Baumgardner M F. Soil Science, 1972, 114: 477. [3] Morra M J, Hall M H, Freeborn L L. Soil Science Society of Am. Journal, 1991, 55: 288. [4] Dalal R C, Henry R J. Soil Sci. Soc. Am. J, 1986, 50: 120. [5] XU Yong-ming, LIN Qi-zhong, WANG Lu, et al(徐永明, 蔺启忠, 王 璐, 等). Acta Pedologica Sinica(土壤学报), 2006, 43(5): 709. [6] HE Xu-sheng(何绪生). Review of China Agricultural Science and Technology(中国农业科技导报), 2004, 6(4): 71. [7] Chang Chengwen, Laird David A. Soil Science, 2002, 167: 110. [8] Malley D F, Yesmin L, Wray D, et al. Communications in Soil Science and Plant Analysis, 1999, 30(7/8): 999. [9] XIE Bo-cheng, XUE Xu-zhang, WANG Ji-hua, et al(谢伯承, 薛绪掌, 王纪华, 等). Agricultural Research in the Arid Areas(干旱地区农业研究), 2005, 23(3): 54. [10] Zheng Lihua, Li Minzan, Sun Jianying, et al. Infrared and Photoelectronic Imagers and Detector Devices, 2005, Proceedings of SPIE, 2005, 5881: 138. [11] SUN Jian-ying, LI Min-zan, TANG Ning, et al(孙建英, 李民赞, 唐 宁, 等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2007, 27(8): 1502. [12] SUN Jian-ying, LI Min-zan, ZHENG Li-hua, et al(孙建英, 李民赞, 郑立华, 等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2006, 26(3): 426. [13] LI Hua-bei, CHEN Bin, ZHAO Jie-wen, et al(李华北, 陈 斌, 赵杰文, 等). Transaction of the Chinese Society of Agricultural Engineering(农业工程学报), 2000, 16(6): 114. [14] Lü Jin, LIN Min, ZHUANG Song-lin(吕 进，林 敏，庄松林). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2005, 25(11): 1790. [15] TIAN Gao-you, YUAN Hong-fu, LIU Hui-ying, et al(田高友, 袁洪福, 刘慧颖, 等). Journal of Instrumental Analysis(分析测试学报), 2005, 24(1): 17. [16] BI Wei-hong, CHEN Jun-gang, LI Lin(毕卫红, 陈俊刚, 李 林). Infrared(红外), 2006, 27(8):16. [17] ZHANG Pei-yao, MA Xiao-jiang, WANG Ji-jun, et al(张佩瑶, 马孝江, 王吉军, 等). Journal of Dalian University of Technology(大连理工大学学报), 1997, 37(01): 69. [18] TAO Li-min, XU Chang-ru(陶立敏, 许昌如). Journal of Wuhan University of Technology(Traffic Science and Engineering Edition)(武汉理工大学学报·交通科学与工程版), 2005, 29(2): 277. [19] FEISI Technology Products Research & Development Center(飞思科技产品研发中心). Wavelet Analysis Theory and Achieve with MATLAB7(小波分析理论与MATLAB7实现). Beijing: Publishing House of Electronics Industry(北京: 电子工业出版社), 2005. [20] McNulty Christopher S, Msuze Ganapati. Proc. SPIE-Int. Soc. Opt. Eng., 1998. 167. [21] TIAN Gao-you, YUAN Hong-fu, LIU Hui-ying(田高友，袁洪福，刘慧颖). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2006, 26(8): 1441.
