https://doi.org/10.37229/fsa.fjh.2026.08.03

This experiment was conducted on potato plants at a private farm at Sin El-Baharya – Badr District Center, Beheira Governorate, Egypt, over the winter season of 2024/2025 and 2025/2026, focusing on the effect of different  irrigation water quantity  (IWQ) (1000, 1250, 1500 and 1750 (m³/fed.), K rates  at 75, and 100 % of the recommended rate (RR) which equal 96 and 72 kg K₂O/fed. respectively, humic acid (HA)  at 0 and 10 kg/fed.  as soil application and their interactions on the growth, and productivity,  potassium  and water use efficiency (KUE and WUE) , and quality of the tubers in a sandy soil. The experiment was carried out in a split-split plot design, in which the irrigation water amounts was the main plot, the sub plot varied the K rates and the HA rate occupied in the sub sub plot.  The triple  interaction among IWQ at 1500 m³/fed. and fertilizing  potato plants  with 75 %  RR which equal 72 kg K₂O kg/ fed. and HA at 10 kg /fed. as soil application was the best  treatment  for enhancing  plant growth and   productivity and KUE.  In addition, this treatment led to a relative increase in the total yield by 5.8% and saved 250 m³/fed. water  than  the interaction among  IWQ at 1750 m³/fed. ,  with the same  of K and HA amounts in both seasons. While, IWQ at 1750 m³/fed.  and fertilizing with  K at 100 % (96 kg K2O/fed.)  and HA  at 10 kg /fed. produced the best tuber quality.  On other side,  the maximum WUE were obtained with  the interaction  among  IWQ at 1000 m³ water/fed., K at  100 % RR and HA at 10 kg /feddan in both seasons.