Investigating the impact of slash and burn (jhum) cultivation on sediment-discharge-nutrient dynamics in high-rainfall tropical hilly catchments

Slash and burn, also known as jhum cultivation, is the oldest agricultural practice in South and Southeast Asia. This study investigated the impact of jhum cultivation on catchment-scale processes, such as streamflow, sediment, and nutrient dynamics. Three experimental catchments, out of which two are under jhum cultivation (JH01 and JH02) and one forested (KF) catchment, in the Mizoram district, India, were identified. High-resolution (15-minute interval) discharge data and discrete storm-event water samples for sediment and nutrient estimation were collected for the period of 2023–2025 water year. Using the observed data, a suspended sediment rating curve was developed for each catchment to calculate the suspended sediment yield. Annual SSY ranged from 0.04 to 2.45 Mg km⁻² yr⁻¹, with JH01 showing the highest variability (CV = 82.6%) and KF showing the lowest variability (CV = 42.3%). Further, we observed a quadratic relationship between discharge ( Q max , runoff and Q mean ) variables and SSY, at jhum catchments; however, an exponential relationship between these variables exists in forested catchment. Q mean , precipitation, and slope together explained 89% variability of fixed and random effects of SSY . Double mass curve analysis showed a significant increase ( p < 0.05) in discharge by17% in JH01 and 43% in JH02 in the post-jhum period. Moreover, post-jhum nutrient loads increased sharply, with potassium increased by 240% in JH01 and 73% in JH02, with corresponding spikes in Ca²⁺, Mg²⁺, NO₂⁻, and TDS.