Colorimetric method to estimate the soil organic matter in karst areas

Abstract

The increase in soil organic matter (SOM) content contributes to themitigation of the effects of global climate change; thus, it is important to knowits levels.However, the SOM analysis can eventually be expensive and timeconsuming, as well as generating toxic waste. The measurement of soil colormay be an indirect method more practical to estimate the SOM than traditionaltechniques. The principal aim of the study was to use color parameters throughthe CIE Lab system and some color indices, such as saturation and rednessindices, to estimate the SOM in a karst area of the municipality of Chetumal inthe Yucatan Peninsula, Mexico. The percentage of SOM was measured in 50 soilsamples by conventional methods while the soil color was analyzed with the CIELab system. Both variables were correlated with the redness index. Based on color,the samples were separated into five groups, ranging from pinkish white to brownishgray. Multiple regression equations (SOM vs soil color parameters) were performedfor each group and a medians comparison analysis was applied. The correlationadjustment between the redness index and SOM is R2> 0.86. The values of themultiple regression equations were R2> 0.8. We conclude that the soil rednessindex, now named soil organic matter index, can be used as a relatively quickapproach to estimate the percentage of SOM in karst areas