Department of Soil Science and Agricultural Chemistry, College of Agriculture, Central Agricultural University, Imphal, Manipur, 795001
*Corresponding author
Thirteen soil test methods for predicting response of rapeseed to sulphur application on thirty-seven surface soils of Manipur were evaluated. The suitability of these extractants was in the descending order: Morgan's reagent > 1 N NH4OAc > 0.5 N NH4OAc + 0.25 N HOAc > 1 N NaOAc > 500 mg P L−1 as Ca(H2PO4)2 + 2 N HOAc > 0.15% CaCl2 > 0.01 M Ca(H2PO4)2 > 0.01 N HCl > 1% NaCl > distilled water > 500 mg P L−1 as KH2PO4. Morgan's reagent extractable sulphur showed the highest and positive correlations with sulphur uptake (control), Bray's per cent yield and uptake. Therefore, this extractant may be used as an index of available sulphur for rapeseed (M-27) grown on acid soils of Manipur, the critical level being 40.0 mg kg−1. The critical limit of sulphur concentration in plant at 40 days of planting was 0.35%.
Sulphur, acid soils, rapeseed, critical limit
