Shifting cultivation or Jhum is a traditional farming method that typically involves cycles of burning and clearing forests (primary orsecondary), cropping for a short time and subsequent abandonment of the site for vegetation regeneration (Ramakrishnan, 2007). It is a practice that has long been associated with the traditional agricultural practices of the indigenous peoples of Northeast India. According to a NITI Aayog report of 2018, about 8500 sq. km. of land in the north east is still used for shifting cultivation. The practice is deeply embedded in social and traditional systems making it a focal point of research for over 50 years. While critics conventionally regard it as economically inefficient and environmentally harmful (Rahman et al., 2012), advocates argue that it is a sustainable practice that promotes agrobiodiversity and enhances the resilience of farmers’ food systems (Raj, 2010; Behera et al., 2016).

One of the major ecological issues in shifting cultivation following land clearing, burning, cultivation and land abandonment is the speed of recovery or revegetation process. When felling cycles extended beyond 50 years in earlier times, shifting cultivation was not considered a destructive agricultural practice. However, due to current land constraints and population pressures, the Jhum cycle in the region has shortened to 7-11 years (Thong et al., 2019) and in some extreme cases, to as short as a single year (Kharlukhi et al., 2023). Consequently vegetation recovery patterns following shifting cultivation have been investigated at many locations across the north east (Gogoi et al., 2020; Sharma et al., 2022; Hombegowda et al., 2024). In all the studies there is an equivocal consensus that longer fallow periods allows better regeneration and vegetation establishment. However in the case of soil, the reclamation processes are not so clear. For instance Oliveira (2008) observed a relatively rapid reconstitution (around five years) of the nutrient capture mechanisms of the dead organicmatter on the forest floor and in the fine roots after theabandonment of the crop area. However, in a review by Ribeiro Filho et al., (2013), a period of ten years of fallow period is considered to be the minimum to avoid soil degradation. Further, recovery also depends on the ratio of cropping period to fallow that describes the relative ability of an agro-ecosystem to maintain soil conditions over the long term. Therefore, it is crucial to monitor changes in soil dynamics across different fallow periods under different agro ecological zones to better understand patterns of land recovery. This will have implications in crop selection, soil working and amendment practices when alternative land usesare recommended on fallow sites.

In the state of Mizoram, the main agricultural practice followed by the inhabitants is jhum (shifting) cultivation (Rathi et al., 2019), with about 32% of the cultivated area under this cultivation (Rohlupuii et al., 2023). The present study aimed to focus on understanding the difference in soil parameters of current jhum land, fallow lands of different ages and natural forest in humid subtropical zone of the state. The district selected for the study is Serchhip which is also the smallest district in the state of Mizoram. The district occupies an area of 1421 km2 out of which 1143.44 km2 is covered by forestwhich is 80.47% of the total geographical area, yet having the second least forest cover per percentage ofgeographical area in Mizoram districts (Forest Survey of India, 2021). As of 2011, the district is one of the three to have large concentration of abandoned jhumlands (Sati, 2019).  

Three study areas under Serchhip district of Mizoram were selected, viz. Buangpui, Chhingchhip and East Lungdar (Fig 1) in the year 2022-23. The altitude of the study areas ranged between 800 and 1100 m above sea level. At each study area, plots of different land uses were surveyed; 0-2 years (where shifting cultivation is being practiced), which are represented as SC (shifting cultivation), 2-4 years (fallow land) as JF₁ which denotes Jhum fallow number 1, 4-6 years (fallow land) as JF₂ which denotes Jhum fallow number 2 and NF (natural forest), i.e. forest which was untouched for at least 30 years.

 

Soil samples were collected from all three sites (viz. Buangpui, Chhingchhip and East Lungdar) and from all the land use of SC, JF₁, JF₂ and NF. Sampling points were taken from areas where physiographical, topographical properties and parent material are as similar as possible. Soil samples were collected by manually operating soil core with knowndimensions at two depths (0-10 cm, 10-20 cm). Each location of sampling points was replicated 3 times. Collected soil sampleswere processed (air dried and oven dried at < 60°C) and sieved using a 2 mm sieve and weighed <2 mm and >2 mm mass. This <2 mm particles are used for further analysis of particle sizeanalysis, pH, OC, N, P and K. Analysis of texture by was carried out as per International Hydrometer method (Brady and Weil, 1996), Bulk density by core sampler method (Black, 1965), pH by distilled water suspensionby a digital pH meter (Jackson, 1973), electric conductivity using an EC meter as per Jackson (1973), organic carbon by the method of Walkley and Black (1934), available Nitrogen was determined by alkaline permanganate method (Subbiah and Asija, 1956), available Phosphorus was determined by the method of Bray and Curtis (1957) and available Potassium was determined by a method as described by Jackson (1973).

Two-way Analysis of Variance (ANOVA) was performed to analyze the various dependentvariables under study viz. Soil pH, Electrical Conductivity (EC), Soil Organic Carbon (SOC), Soil Organic Matter (SOM), Available Nitrogen (N), Available Phosphorous (P) and Available Potassium (K) after duly checking the basic assumptions of ANOVA. The significance of different land use, different depth increments and land use with depths wasseen by the use of Operational Statistics (OPSTAT) software. Other computations andanalysis were completed using MS Excel 2019.

Linear models with the soil parameters as the response variables individually and the age of the site as the predictor variable was used to check for a significant change in soil parameters with age. To use ‘age of the site’ as a continuous variable for thelinear models, SC was assigned 2 years, JF₁ 4 years, JF₂ 6 years and NF 30 years.

The percentage of sand, silt and clay did not vary significantly among the different land uses and soil depth at Buangpui and East Lungdar. At both the sites, soilswere sandy loam in nature. However, significant variations were observed in the soil textural components at Chhingchhip (Table 1). The sand percentage was lower in fallow sites compared to the current Jhum site, but higher in natural forests making the soil. Since soil texture is primarily determined by geological processes and is generally resistant to change, the observed differences cannot be directly attributed to the length of the fallow period but to factors such as parent material, micro climate and topography differences. In all three sites pH of soils was acidic (Table 1), but variation across land uses were non- significant except at Buangpui. The soils of Mizoram are generally acidic with pH values ranging from 4.27 to 5.43 in the present study. Brajendra et al., (2016) reported over 80% of soil sampled from 7 district of Mizoram under different landuses to be acidic in nature. The bulk density did not vary significantly between different land uses in 2 of the 3 sites, but it was generally higher in current Jhums and fallow lands compared to natural forests. Low bulk density in natural forest can be primarily linked with higher SOC values that contribute to proper soil aeration, a relation well established (Kumar et al., 2023). Results of the linear regression analysis further showed significant increase of SOC with age of fallow period at 0-10 cm soil depth (Table 2). Higher bulk density was recorded at 20-40 cm compared to the upper layers in most land uses and sites. This tendency of bulk density to increase with depth could simply be attributed to the cumulative physical weight of soil material above it,  leading to higher soil compaction in the lower depths (Yadav et al., 2019) and the reduced soil porosity due to lower SOC content in the lower depths (Abad et al., 2014). Although EC values did not vary significantly among different shifting cultivation fallow landscapes, regression analysis indicated that fallow age had a significant positive effect on EC, with increasing fallow period associated with higher EC values (Table 2).





Soil organic carbon (SOC) and phosphorus displayed rising levels with age of fallow period (Table 3). For SOC, the variation among the land uses was significant in all sites and top layer of the soil was consistently higher in SOC content. The SOC content recorded for the top soil layer of current Jhum ranged from 1.52% at Chhingchhip to 2.69% at East Lungdar. The SOC content conforms to the average of 2.32% reported by Kenye et al., (2019) for 6 current Jhum sites across Mizoram, but much higher than that reported by Madhurima and Mishra (2023) nearby Aizawl city. Buangpui natural forest recorded the highest SOC content (4.96%) and Chhingchhip the lowest in (2.67%). Buangpui natural forest is reported to have highest shrub density and basal area compared to other two sites, along with comparatively high tree and herb density (Lalnungrenga et al., 2024) which can be a major contributing cause for the high organic matter content. Further the altitude of Bungapui which is the lowest amongst the other sites can augment litter decomposition process for comparatively high SOC buildup.



Available phosphorus was lowest in current Jhum sites cultivated for more than one year at Buangpui and Chhingchhip (Table 3). Burning of slash in shifting cultivation, although releases phosphorus stored in the biomass and temporarily increases its level, it is subsequently absorbed by cultivated crops and lost due to run off and erosion. Further, absence of any external inputs in shifting cultivation practices of the Mizo community perhaps drains these nutrients at a faster rate. As natural vegetation regenerates during the fallow period, there is an accumulation of phosphorus, a trend also observed in fallow sites in Nagaland (Temjen et al. 2022) and corroborated by another study in Mizoram (Sharma et al., 2022). As the age of the fallow period increases, the vegetation becomes dominated by larger shrub and tree species. These higher plants possess deep root systems that can efficiently transport phosphorus from the lower to upper layers of soil  (Lawrence and Schlessinger, 2001). Furthermore, landscapes with longer fallow periods support greater vegetation and accumulate larger amounts of decaying vegetation, which contributes to increased levels of phosphorus in soil (Neha et al., 2020).

Highest available nitrogen levels were recorded in current Jhum plots at all sites with Buangpui and East Lungdar reporting 658.22±14.41 kg/ha and 649.60±11.86 kg/ha (Table 3). This is expected because post burningnitrogen is either released from organic matter (Ekinci, 2006) or added in the form of unburned on partially burned materials in the soil (Kyuma et al., 1985). Contrary to other studiesin Mizoram (Temjen et al., 2022; Sharma et al., 2022), we observed a decline in available nitrogen with increase in fallow ages, i.e between 2-4years and 4-6years. It is possible that the assessment interval was too short to capture any meaningful recovery, as several studies have reported that available nitrogen can continue to decline for up to 15 years following burning (review by Arunrat et al., 2023). The available nitrogen of natural forests ranged from 378.58 kg/ha to 415 kg/ha and is much higher than that reported by Madhurima and Mishra (2023) and Nemhoihkim et al., (2025) for other forests sites in Mizoram. There is large fluctuation in the levels of available K among land uses at different sites. It is highest in current Jhum at Buangpui (821 kg/ha), in 2-4 years fallow at Chhingchhip (391 kg/ha) and, in 4-6 years fallow at East Lungdar (828 kg/ha). Although K levels usually increase after a fire due to the combustion of organic matter (Arunrat et al., 2023) their availability may be reduced due to rainfall, washing away K through particulate transport of ash, runoff, or erosion or through the uptake by growing vegetation (Xue et al., 2014; Fonseca et al., 2017). However, K levels may recover overtime as litter fall increases and decomposition process becomes more active (Manjunatha and Singh, 2020). The amount of available K was however consistently lower in the 10-20 cm soil depth compared to 0-10 cm.

The analysis of soil physical properties revealed significant difference in bulk densities of soils obtained from different land uses. HoweverpH and EC did not show any significant difference or pattern. Organic matter and phosphorus build up was evident as age of fallow progressed at all sites and was highest in natural forests. Linear regression analysis revealed significant increase in EC and SOC with age of fallow period. Available nitrogen was found to decline and available potassium inconsistent with increasing fallow period, which in the present study was limited to only up to 6 years indicating the need to include older fallow periods for more conclusive outcomes.

All authors declare that they have no conflict of interest.