EFFECT OF SULFUR FERTILIZATION ON RAPESEED AND PLANT AVAILABE SULFUR IN SOILS OF POTHWAR, PAKISTAN

A field study was conducted to assess the effect of different sulfur (S) fertilizers on rapeseed crop and plant available S (SO4-S) status of two S-deficient soils. These soils were located in Pothwar, rainfed areas of Pakistan. Three S fertilizers were applied at five different levels (0, 10, 20, 30 and 40 kg S ha-1). The three S fertilizers increased the rapeseed yield and yield parameters in order of ammonium sulphate (AS) single super phosphate (SSP) gypsum, though their effect was at par with each another. The 40 kg S ha-1 produced highest biomass (9058 kg ha-1) , seed yield (1656 kg ha-1) and plant S content (0.158 g 100 g-1), but these increases were statistically at par with that of 30 kg S ha-1 . The highest mean S uptake of 17.0 kg ha-1 was recorded in soil fertilized with AS at 30 kg ha-1 . The different S fertilizers increased S (SO4-S) contents of soil in order of SSP gypsum AS. The highest SO4-S (6.8 MUg g-1) was recorded in the plots where SSP was applied followed by gypsum application. Whereas the application of AS resulted in the least increase in SO4-S (6.0 MUg g-1). Application of S fertilizer also resulted in significantly higher SO4-S content in the 15-30 cm depth soil than in the superficial soils (0-15 cm) at the end ofeach harvesting season. The relationship between S in soil and rapeseedplants was stronger (r = 0.66**) at Chakwal than at Rawalpindi (r = 0.36). The successive application of S fertilizers helped increase plant available S despite growing high S-requiring crop in soils prone to high leaching losses. A regular S fertilization is therefore, required for higher production of higher S requiring crops in this area