Relative Efficiency of Two Sulfur Sources Regarding Nitrogen Fixation and Yield of Chickpea

Field experiments were conducted at two different locations (Barani Agriculture Research Institute Chakwal and farmer's field in Talagang) in northern rainfed Punjab, Pakistan, to assess relative efficiency of two sources of sulfur (S) in enhancing nitrogen (N) fixation and yield of chickpea (Cicer arietinum L.). The treatments were four combinations of two levels of S (15 and 30 kg ha(-1)) from two sources [gypsum and ammonium sulfate (AS)] and a no-S control. Application of S significantly increased seed yield up to 12% and 14% at Chakwal and Talagang, respectively. Response (kg seed yield kg(-1) S) at economic optimum dose (EOD) was greater for AS than for gypsum. Sulfur application enhanced the S uptake at both locations significantly. Sulfur harvest index and S economic yield efficiency ratio were greater at Talagang than at Chakwal. Sulfur application resulted increases in N uptake by 19% and 20% and N fixation by up to 19% and 30% at Chakwal and Talagang, respectively. Ammonium sulfate was more effective in increasing N fixation and uptake as compared to gypsum at Chakwal, whereas the difference between the two sources was nonsignificant at Talagang. Thus, it can be concluded that S should be applied to chickpea crop to enhance yield and improve soil fertility status as result of greater amount of N fixed.