Use of infrared spectroscopy and geospatial techniques for measurement and spatial prediction of soil properties

Abstract

The main aim of this research was to assess the use of mid-infrared (MIR) spectroscopy and geostatistical model for the evaluation and mapping of the spatial variability of some selected soil properties across a field. It is with the view of aiding site-specific soil management decisions. The performance of the model for the prediction of the components (soil parameters) was reported using the coefficient of determination (R 2) and root mean square error (RMSE) values of the validation data set. Results revealed that least square regression model performed better in predicting cation exchange capacity-CEC (R 2 ¼ 0.88 and RMSE ¼ 8.98), soil organic carbon-OC (R 2 ¼ 0.88, RMSE ¼ 0.55), and total nitrogen-TN (R 2 ¼ 0.91 and RMSE ¼ 0.04). The first five principal components (PC) accounted for 78.17% of the total variance (PC1 ¼ 25.75%, PC2 ¼ 18.06%, PC3 ¼ 13.85%, PC4 ¼ 11.12%, and PC5 ¼ 9.39%) and represented most of the variation within the data set. The coefficient of variation ranged from 6.73% for soil pH to 57.02% for available phosphorus (av. P). The soil pH values ranged from 4.21 to 6.57. The mean soil OC density was 2.14 kg m À2 within 50 cm soil depth. Nearly 96-97% of the soils contained av. P and sulfur (SO 4 2À-S) below the critical levels. The overall results revealed that soil properties varied spatially. Hence, we suggest that mapping the spatial variability of soils across a field is a cost-effective solution for soil management.

Spatial analysis and mapping of intensity and types of agricultural salt-affected soils around Abaya and Chamo Lakes, South Ethiopia Rift Valley

“…Using interpolation techniques, the spatial prediction and mapping of the un-sampled surface from laboratory point values were carried out in a GIS environment. From laboratory point data, the un-sampled surface was predicted and mapped using the standard kriging algorithm in QGIS [ 52 ]. The map of the preliminary layers of the salt-affected soil indicator, including pH, EC, and ESP, and the predicted final salt-affected soil distribution map was generated.…”