Effect of long term fertilizer use on sulphur availability to rice in an Inceptisol

Abstract

In a long term fertilizer experiment with rice-rice cropping sequence, the changes brought about in the available sulphur status of soil were studied. Available sulphur status decreased from 20 to 9.5 ppm when S-free NPK fertilizers were used for 13 years, whereas it increased to 30.8 and 39.5 ppm, when NPK fertilizers containing 45 and 67.5 kg sulphur were applied per hectare per season, respectively. With the application of S-free NPK fertilizers, there was 21% decrease in grain yield in kharif but no decline in yield was noticed in the summer crop because of the addition of around 10 kg S/ha through irrigation water. Over the period a positive response to sulphur in kharif rice in most of the years was observed and its magnitude increased with the progress of cropping cycles. This indicated that an application of 44 kg S/ha/cropping cycle would be necessary to maintain the sulphur status of the Inceptisol.