Status and distribution of available sulphur in tea-growing soils of Bangladesh

Abstract

This study assessed the distribution and fertility status of available sulphur in tea-growing soils of Bangladesh using 132 paired soil samples collected from 13 tea estates at depths of 0-23 cm and 23-46 cm. Available sulphur was determined using a 0.15% calcium chloride extraction, followed by turbidimetric measurement of barium sulphate. Surface soils contained 0.12 to 69.13 mg/kg available sulphur and sub-surface soils contained 0.58 to 61.00 mg/kg, with mean values of 15.61 and 15.47 mg/kg, respectively. Based on critical limits, 44.70% of surface samples and 47.73% of sub-surface samples were in the low category, indicating a widespread risk of sulphur deficiency. Marked estate-wise variation was observed. Bilashcherra Experimental Farm, Karnafuli, Kazi and Kazi, and Karotoa showed comparatively high mean values, whereas Allynugger, Malnicherra, BTRI Farm, and Sathgao remained in the low range. Available sulphur was positively associated with soil pH and organic matter at both depths, and the relationship with organic matter was strongest in the sub-surface layer. Mean sulphur concentration did not differ significantly between the two depths, but the wide within-estate and between-estate variation indicated that blanket fertilizer recommendations would be inefficient. The study provides a baseline for site-specific sulphur management in Bangladesh tea soils.