Soil Physical and Chemical Attributes Across a Fallow Period of Shifting Cultivation in Ban Mae San, Northern Thailand

Shifting cultivation is often credited with ecological benefits once land is left fallow, yet how long that fallow period must last before soil properties recover remains poorly defined. This study examined soil physical and chemical recovery across a fallow chronosequence spanning one to seven years in northern Thailand. This research aims to identify the fallow duration at which soil functions approach a forest-like state. Soil samples from fallow plots of varying ages were compared against actively cultivated fields, orchards, and undisturbed natural forest. Soil physical properties—including bulk density and porosity—alongside available nitrogen, phosphorus, and potassium, remained statistically stable across the evaluated fallow stages. No statistically significant differences (p > 0.05) were observed when comparing these shifting cultivation stages to the natural forest soils. These quantitative results indicate that instead of a dynamic temporal trajectory, the local shifting cultivation system maintains a steady-state baseline, sustaining soil physical structure and nutrient pools at levels equivalent to the natural forest ecosystem. Most notably, seven-year fallow plots recorded the highest soil organic carbon and organic matter contents among all fallow ages, with a carbon stock of 77.85 ± 8.11 Mg ha−1 that matched, and slightly exceeded, the 76.76 ± 12.09 Mg ha−1 measured in adjacent natural forest. This highlights the potential of traditional shifting cultivation as a climate-resilient land-use practice for regional climate change mitigation.