Cotton root activity measured by triphenyltetrazolium chloride (TTC) had significant effect on treatments applied. There was no significant difference among the treatments applied from 83 to 91 days after transplanting. However, high PK, low K and low P significantly affected cotton root activities beyond 91 DAT. This could be due to variation in room temperature of dehydrogenase activity root as evaluated by the TTC method during the growth stage (McMicheal, and Burke 1994).The planting environment of this current study varies between 20 to 35 o. On the other hand, differences between the varieties (Zhong and Xin cultivars) reveal the genetic makeup of the plants (Jiang et al., 2008).