ABSTRACT

The study was carried out to derive pedotransfer (PTFs) and spectrotransfer (STF) functions to estimate soil organic matter (SOM) content measured by time-consuming and expensive Walkley–Black wet combustion (W-B), using SOM content obtained from loss on ignition (LOI) and spectra reflectance bands at visible (Vis) and near infrared (NIR) regions. In total, 171 soil samples were collected from calcareous soils of southern Iran. The SOM content of the samples was determined using W–B wet combustion (SOM_W-B) and LOI at temperatures of 360 °C during 2 h (LOI_360-2); 550 °C during 3 h (LOI_550-3); and 375°C during 16 h (LOI_375-16). For the spectroscopy method, partial least squares regression (Spect_PLSR) and forward stepwise multiple linear regression (Spect_SMLR) approaches were used for function development. The LOI_360-2 procedure with R²_val of 0.9 for the validation dataset provided the best match with SOM_W-B content. Furthermore, the Spect_SMLR provided a STF using spectral reflectance bands at 495, 730, 970, 1906, 2262 and 2342 nm which predicted SOM_W-B with R²_val of 0.87. Results indicated both the Spect_SMLR and LOI_360-2, as easy and inexpensive approaches, could be recommended to accurately assess SOM content of calcareous soils.

摘要

该研究旨在推导土壤有机质 (PTF) 和光谱传递 (STF) 函数，使用从烧失量获得的 SOM 含量估算通过耗时且昂贵的 Walkley-Black 湿式燃烧 (WB) 测量的土壤有机质 (SOM) 含量(LOI) 和可见 (Vis) 和近红外 (NIR) 区域的光谱反射带。总共从伊朗南部的钙质土壤中采集了 171 个土壤样品。样品的 SOM 含量使用 W-B 湿式燃烧 (SOM _W-B ) 和 LOI 在 360 °C 的温度下 2 小时 (LOI _360-2 ) 测定；3 小时内 550 °C (LOI _550-3 ); 16 小时内 375°C (LOI _375-16 )。对于光谱法，偏最小二乘回归（Spect _PLSR) 和正向逐步多元线性回归 ( _{Spect SMLR} ) 方法用于功能开发。^{验证数据集的 R 2} _val为 0.9的 LOI _360-2程序提供了与 SOM _W-B内容的最佳匹配。此外，_{Spect SMLR}使用 495、730、970、1906、2262和 2342 nm 的光谱反射带提供了 STF，其预测 SOM _W-B，R ² _val为 0.87。结果表明，可以推荐使用_{Spect SMLR}和 LOI _{360-2作为简单且廉价的方法来准确评估钙质土壤的 SOM 含量。}