Rapid Evaluation of Soil Quality Based on Soil Carbon Reflectance

Abstract

Many studies have considered spectroscopy for measurement of soil carbon (SC), and there is potential for spectroscopy to be used as a cost and time effective approach to assess soil quality (SQ). In this research, the relationship between SC and SQ in Irish grassland soils was studied; particularly the efficiency of spectroscopy and chemometric techniques for assessing SC and its contribution to SQ. The study was conducted using 20 sites with 5 replicates per site (n = 100 soil samples). Twenty soil properties were measured using standard methods as soil quality indicators. Management intensity was classified using K- means clustering, and the results reflected a trend in soil properties indicative of poorer SQ under more intensive management. Soil porosity, CN ratio and SC were selected as a minimum data set using principal component analysis and SC was the most discriminating indicator of the impact of management intensity on SQ. Soil visible and near- infrared spectra showed a good efficiency (R-2 = 0.91, RMSE = 0.4, RPD = 2.94) for prediction of SC. Spectroscopy and chemometric analysis allowed rapid evaluation of SC, and because of the strong relationship with management intensity, can provide a rapid, low cost, quantitative method for evaluating SQ under grassland management.