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Soil Microbial Biomass (SMB) dynamics in rainfed wheat fields was assessed. In study 1/2 NP @ of 40: 20 kg ha(-1) and full recommended dose of NP @ of 80: 40 kg ha-1 was applied. A composite soil sample was taken and its electrical conductivity (ECe) was 0.38 dS m(-1). SMB parameters such as C-mic, N-mic, P-mic, C-mic: N-mic and C-mic: P-mic were determined by fumigation extraction method. The C-mic, C-mic: N-mic and C-mic: P-mic values were highest at the early stage of crop then declined in the middle and lowest at the crop maturity. Whilst N-mic and P-mic were low in the initial growth period and at peak in middle and lowest at maturity. All indices of SMB were increased by utilization of a balance fertilizer as in CK, the total amount of C-mic, N-mic, P-mic, C-mic: N-mic and C-mic: P-mic during wheat growth was 861.08 mg kg(-1), 84 mg kg(-1), 31.91 mg kg(-1), 83.81 mg kg(-1) and 224.19 mg kg(-1), respectively. In 1/2 NP dose it was 1260.4 mg kg(-1), 104.07 mg kg(-1), 45.69 mg kg(-1), 98.35 mg kg(-1) and 230.33 mg kg(-1), respectively whilst in NP dose it was 1435.42 mg kg(-1),112.68 mg kg(-1),59.65 mg kg(-1),102.78 mg kg(-1) and 198.5 mg kg(-1), respectively. Seasonal variation depicted prevalent effect on SMB in the study. The average values of C-mic, C-mic: N-mic and C-mic: P-mic during drought period were higher than in rainy season. SMB fluctuation was ambient with regard to change in air and soil temperature. The considerable seasonal changes and variation due to fertilization in SMB indicated a direct relationship with nutrients availability which shed impact on growth and yield of crop.