Changes in the Status of Water Soluble Sulphur and Available Micronutrients in Soil as a Result of Intensive Cropping and Manuring

An assessment of the status of water soluble sulphur and available micronutrients has been made in a long-term field experiment at the I.A.R.I. Farm, New Delhi on an alluvial sandy loam soil. During the period 1973–75 extending over five successive crops (2 wheat, 2 pearl millet and 1 cowpea), application of sulphur carrying fertilizer, (P supplied as single superphosphate) significantly increased sulphate sulphur in soil as compared to the treatments in which diammonium phosphate was used as phosphorus source. Annual application of zinc sulphate (10 kg/ha) along with NPK raised the available Zn status to about three times the amount recorded with the application of NPK only. Fertilizer treatments resulted in a two-fold rise in available Fe content and even in control plots the increase was by about 50 per cent. Addition of zinc significantly enhanced the available Mn in soil, the status of which remained nearly at the same level with NPK and FYM treatments, whereas there was a marked decline in control plots. In all cases, the status of available Cu showed an improvement (by about 0.4 to 0.6 ppm) with cropping, there being no differential effect due to treatments.