Soil quality change 50 years after forestland conversion to tea farming

Land-use change has been shown to affect soil quality and may lead to soil degradation. The effects of land-use change from natural forest to tea farming on soil properties and quality were studied within Guilan Province of northern Iran. Thirty-six soil samples (0–30 cm) were randomly collected from six sites with three replications at each site. The soil quality of forest and tea farms was determined using the cumulative rating (CR) index and the Cornell Comprehensive Assessment of Soil Health (CASH) scoring function. Effects of land-use change on soil quality or health were significant (P < 0.01) using both methods. Both methods for all regions (forest and tea fields) showed that forest land-use was more sustainable based on lower CR (lower limitation to crop production) and higher CASH scores (higher soil productivity and quality) than tea farm soils. Both methods were also negatively correlated with each other. Despite pH being a limiting factor for soil quality, it was not influenced by land-use change in most locations because the studied soils were acidic. However, organic carbon was the most important soil quality indicator, which was significantly correlated with soil physical, chemical and biological (respiration rate) properties. Therefore, land-use management practices that are continuously cultivated should include increases in organic carbon.