Abstract: The comprehensive effects of the timing of watering and N and K fertilization(D),amount of irrigated water(W),and application rates of chemical N and K fertilizers,and farm manure(M) were studied by the design of orthogonal regression rotation with five factors and five levels under dry greenhouse condition.The N utilization efficiency of potato was in order of N>W>D>M>K.Under different application rates of W,N,K and M,the N utilization efficiency was significantly increased with optimum timing of watering and fertilization.When the application rate was low,the timing should be earlier,while it was high,the timing should be later.High application rates of W and N resulted in the best interaction effect,with 57.83% of N utilization efficiency;moderater W and N or low W and N had 29.17～40.99% of efficiency;and high W and low N or low W and high N resulted in the lowest efficiency,with 22.87% and 22.51%,respectively.

Key words: Potato, Watering and fertilization, N utilization efficiency