Status and Distribution of Sulphur in Acid Soils of Imphal East District, Manipur

A pot experiment was conducted with thirty soils of varying characteristics for selecting the most suitable chemical extractant for available sulphur. Rice variety CAU-R1(Tamphaphou) was grown in pots treated with and without sulphur for eight weeks. At harvest dry matter of rice was recorded. The average dry matter yield increased significantly @30 kg ha-1 levels of S application. Sulphur in the soils was extracted with four different extractants. The extractable S of the soils varied considerably with the soils and the extractant used. In term of the efficiency of extraction,the extractants were in the order : 500 ppm Ca(H2PO4)2.H2O > 0.5M NaHCO3 > 0.5M NH4OAc > 0.15% CaCl2. Available sulphur extracted by 0.5M NH4OAc showed the highest correlation with Dry Matter Yield (0.510882**) , Total Plant Uptake (0.548974**), Bray’s % Yield (0.514887**), Bray’s % Uptake (0.70565**).Therefore,0.5M NH4OAc extractant was rated as most promising extractant for assessing S availability for rice in acid soils of Manipur. pH (-0.12481, -0.04153837, 0.15850443, -0.02106*), EC (-0.2696*,-0.08246, -0.21701*,-0.28734*),CEC (-0.27441*, -0.24183*, -0.18531, -0.28287*), sand (-0.00152, -0.0166 , -0.10168, 0.121165), silt (-0.00858 , -0.15039, -0.10699, 0.030722), Ca2+ (-0.1528, -0.1056 , 0.007184 , -0.09847) and Mg2+ (-0.27248*, -0.16614, -0.07896, -0.24056*) had negative correlations with all extractants of S. The positive relationships of almost all extractants of sulphur with clay texture (0.040966, 0.20296*, 0.306651**,-0.0879), organic carbon(0.096396, 0.32224**, 0.201351*, -0.09377), nitrogen (0.036851, 0.203472*, 0.24579*, -0.06179), phosphorus (0.301882**, 0.268273719*, 0.322386047**, 0.209681*) and potassium (0.023932, -0.00667852, -0.04825616 , 0.079524) were observed.