Effect of sulfur fertilization on rapeseed and plant available sulfur in soils of Pothwar, Pakistan.

摘要

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 superphosphate (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 micro g 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 micro g 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 of each harvesting season. The relationship between S in soil and rapeseed plants 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.