土壤全氮田间Vis/NIR光谱测定方法研究

应用Vis/NIR光谱直接测定原始土壤属性具有重要的研究和应用价值。选取我国中部水稻土和潮土共103个土样，对比分析了两种土壤在田间环境下的湿态(R_w)和干态(R_d)光谱特征。采用相对变换光谱方法对湿态光谱进行了处理，结果表明该方法能够有效降低土壤水分的干扰和消除部分噪声，得到的变换光谱(R_n)与干态光谱在信息量和特征方面具有很高的相似度。以此建立了土壤TN的PLS回归估计模型，检验结果表明，R_n对水稻土和潮土TN的估计模型精度均高于R_w，修正判定系数分别从0.26和0.46提高到0.53和0.62。因此，相对光谱变换方法能够有效提高应用田间土壤光谱估计土壤参数的能力，建立的PLS模型可以用于测定TN含量，研究结果可作为实现田间实时分析土壤属性的工作基础。

In-site Total N Content Prediction of Soil with Vis/NIR Spectroscopy

The Vis/NIR spectroscopy as an efficient tool to predict within-filed soil properties is significantly valuable when establishing agricultural field trials and in precision farming.The object of the study was to investigate the feasibility and possibility of using transformed in-site spectra by relative transformation method(RTM)to prediction soil properties.One hundred and three samples of paddy and fluvo-aquic soil in central china were collected.The in-site moisture(Rw)and dried(Rd)Vis/NIR spectra were measured by ASD field handHeld analyzer.The spectral characteristics of two kind soils were analyzed comparatively.The Rw spectra were transformed by RTM into Rn,which were of similar information content and charatistics with Rd.The first derivatives of three spectra revealed that the method could reduce the water disturb on and noise in Rw Vis/NIR spectrum.The PLS regession model was applied to predict total nitrogen(TN)respectively using Rw,Rd and Rn as predictor.The models with Rw predicted TN respectively of paddy,fluvo-aquic and all samples with poor adjusted r2(<0.5),while Rd with good adjusted r2 0.70,0.88 and 0.71 and Rn 0.53,0.62 and 0.64.The result showed that the RTM was efficient to enhance analysis and prediction of soil properties using Vis/NIR spectrum measured on the spot.The combination of PLS and RTM could help implemention of real-time analyzing soil properties using Vis/NIR spectrum.