Two experiments were conducted at Al-erra and Dhamar research farms belonging to Northern Highland Research Station and Central High-land Research Station of Agricultural Research & Extension Authority. The soil characteristics of the experimental sites where silty- clay loam and clay loam for both sites respectively, with low content in organic matter and total nitrogen. The two experiments were initiated in March, 2000 in a randomized block design with five replications. The experiments included the following treatments: N1=50kg/ha;N2=100kg/ha;N3=150 kg/ha;N4=200kg/ha (fertigated treatments) and Ns=150 kg/ha (surface nitrogen application).Labeled fertilizer was applied to subplot within fertigated plots  in order to determine the total N uptake by plant  and fertilizer N use efficiency. The objective of this study is to investigate the effect of the surface nitrogen application with fertigation, on yield, water and nitrogen use efficiency of potato crop variety (Daimont). Results indicated that, the surface application treatment (Ns) tend to give a better yield compared to fertigated treatments (N1, N2, N3, and N4) without significance differences in Al-erra location, but significantly differed in other location. The total and marketable yield didn't increase significantly with an increase in N rates. Concerning the dry matter weight of tuber, the fertigated treatment (N3) gave a better yield than all treatments including surface application treatment (Ns), followed the treatment (N2). Parameters related to water and fertilizer use efficiency, consumed water per unit dry matter and total fresh yield, all fertigated treatments gave significantly higher yield than surface application treatment (Ns). This study showed  that, the drip system and method of fertigation used can potentially save water usage by 50% without any reduction in yield compared with that obtained with the surface application treatments. In addition, the efficient use of N fertilizer was high for all fertigation treatments compared to the surface application (Ns).

Keywords: Nitrogen fertilizer, Irrigation system, Fertigation, potato, water use efficiency, fertilizer N use efficiency , 15N- labelled