Organic matter determination in arid region soils: loss-on-ignition versus wet oxidation

ABSTRACT

The precise assessment of soil organic matter (SOM) is required when studying soil pedology, chemistry, physics, and fertility. Besides, it is a key for evaluating soil quality, plant growth, and sustainable land management. This research aims to correlate the SOM resulted from loss-on-ignition (LOI) with those from wet combustion (Walkley–Black, WB). A total of 130 soil samples were collected from Egypt and analyzed using WB and LOI. In LOI, samples exposed to the combustion temperatures of 300, 375, 430, and 550°C for 2 and 4 hours. Using RStudio, simple linear regressions were conducted to estimate the most suitable temperature/time combinations. The results showed that applying lower temperatures (300 and 375°C) for 2 hours provided a strong correlation between LOI and WB with R² of 93 and 94% for all dataset and sandy soils, respectively. For clay soils the respective R² values at 300 and 375°C were 83 and 85%. The proposed combinations were valid to estimate SOM content for different soils with correlation up to 0.99 for sandy soils.

KEYWORDS:

• Regression analysis
• RStudio
• Walkley–Black
• sandy soils
• clay soil

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.