Spatial Variation of Soil Fertility in North Sikkim, India

Abstract

A research investigation was carried out in 2024 to evaluate the spatial variation of soil nutrients in soils of North Sikkim across five regions viz. Mangan, Dzongu, Ringhim, Kabi, and Chungthang through real-time analysis of soil fertility parameters, taking 3,750 samples. Key parameters assessed included pH, electrical conductivity (EC), organic carbon, macronutrients (nitrogen, phosphorus, potassium, sulphur), and micronutrients (zinc, boron, iron, Manganese, and copper). To analyze 3,750 soil samples with uneven distributions, weighted statistical methods were used to account for sampling variability. Mean comparisons were conducted using One-way ANOVA, followed by Duncan’s Multiple Range Test at a significance level of α =.05 to assess statistical differences and classify locations based on their similarity in soil characteristics. The results indicated a highly acidic soil environment, with pH ranging from 4.865 ± 0.021 to 4.880 ± 0.020, potentially affecting nutrient availability. Organic carbon levels ranged from 0.50% ± 0.050 to 0.70% ± 0.047. Nitrogen and phosphorus were critically deficient, which ranged from 157.9 ± 9.86 to 161.234 ± 10.102 kg/ha and from 18.9 ±1.430 to 19.4 ± 1.435 kg/ha, respectively, posing significant constraints for crop productivity. Potassium was at a medium level (233.92 ± 7.800 kg/ha to 236.3 ± 7.708 kg/ha), while sulphur, zinc, and copper were within adequate ranges. However, the study revealed excessive iron concentrations (mean: 98.18 ±0.222 mg/kg) and widespread boron deficiency (mean: 0.282 ± 0.002 mg/kg), which could lead to physiological disorders in crops. The findings emphasized the urgent need for restoring soil pH and improving overall soil health. It was observed from elaborate analyses that distance among the study regions and DEM derived variables also influenced spatial distribution of soil fertility characteristics. Insights from the current soil testing would drive the implementation of balanced nutrient management strategies, optimizing soil fertility and ensuring sustainable agricultural productivity. Given Sikkim's distinction as the world's only fully organic state, these measures are essential for preserving the productivity of high-value crops such as ginger, large cardamom, cherry pepper, and vegetables. This study would serve as a foundational step in retaining Sikkim's significance as the only organic state on the global map through the holistic management of soil health, ensuring long-term sustainability and productivity.