A 2-year experiment was conducted in cinnamon soil in the eastern parts of Hebei Province and the effects on the space-time
dynamic changes of soil P and K nutrient with returning application of maize straw were studied. The results showed that returning application of maize straw could significantly improve the supply of soil P and K. In the stage of wheat growing, P
transformation with returning application of maize straw indicated the characteristics as follows: net release in the previous period, net fixation in the middle and net release in the later period; while K transformation showed huge release in the previous period, but reduction step by step in the middle and later period. Adjusting the proportion of straw C/N from 15∶1 to 35∶1, the course of transformation with application of maize straw did not change, and there was no obvious difference to the space-time dynamic variations of soil P and K. Adjusting the straw proportion of straw C/N with
transformation promoter could remarkably quicken the step of transformation of maize straw.