Vocational School of Technical Sciences, Uludag University, Bursa 16059, Turkey.
Sensors (Basel). 2013 Aug 8;13(8):10177-90. doi: 10.3390/s130810177.
This paper aims at exploring the potential of visible and near infrared (vis-NIR) spectroscopy for on-line measurement of soil pH, with the intention to produce variable rate lime recommendation maps. An on-line vis-NIR soil sensor set up to a frame was used in this study. Lime application maps, based on pH predicted by vis-NIR techniques, were compared with maps based on traditional lab-measured pH. The validation of the calibration model using off-line spectra provided excellent prediction accuracy of pH (R2 = 0.85, RMSEP = 0.18 and RPD = 2.52), as compared to very good accuracy obtained with the on-line measured spectra (R2 = 0.81, RMSEP = 0.20 and RPD = 2.14). On-line predicted pH of all points (e.g., 2,160) resulted in the largest overall field virtual lime requirement (1.404 t), as compared to those obtained with 16 validation points off-line prediction (0.28 t), on-line prediction (0.14 t) and laboratory reference measurement (0.48 t). The conclusion is that the vis-NIR spectroscopy can be successfully used for the prediction of soil pH and for deriving lime recommendations. The advantage of the on-line sensor over sampling with limited number of samples is that more detailed information about pH can be obtained, which is the reason for a higher but precise calculated lime recommendation rate.
本文旨在探讨可见近红外（vis-NIR）光谱技术在土壤 pH 在线测量中的潜力，以期生成可变率石灰推荐图。本研究使用了安装在框架上的在线可见近红外土壤传感器。基于 vis-NIR 技术预测的 pH 值生成的石灰应用图与基于传统实验室测量 pH 值生成的图进行了比较。离线光谱验证校准模型提供了 pH 值的优异预测精度（R2 = 0.85、RMSEP = 0.18 和 RPD = 2.52），而在线测量光谱则获得了非常好的精度（R2 = 0.81、RMSEP = 0.20 和 RPD = 2.14）。与离线预测的 16 个验证点（0.28 t）、在线预测（0.14 t）和实验室参考测量（0.48 t）相比，所有点（例如 2,160）的在线预测 pH 值导致总体田间虚拟石灰需求最大（1.404 t）。结论是，可见近红外光谱技术可成功用于预测土壤 pH 值和推导石灰推荐量。与使用有限数量样本进行采样相比，在线传感器的优势在于可以获得更详细的 pH 信息，这也是计算出更高但精确的石灰推荐率的原因。
