**4. Summary and Conclusions**

In arid regions, suitable irrigation techniques and regimes are highly important in order to acquire a profitable yield. Potato growth is mainly limited by two factors: Water and nitrogen availability. Excess irrigation can reduce tuber yield due to insufficient oxygen in the root zone and increase nutrient loss through leaching, which can also result in ground water contamination. Deficit irrigation may result in decreased tuber yield due to lack of water and a reduction in tuber quality through unavailability of nutrients or salt accumulation. Moreover, improper plant development will result in smaller foliage and thus reduced photosynthesis per unit leaf area.

Our results demonstrate that a sequential practice of sprinkler irrigation for the germination phase followed by low discharge drip irrigation can result in similar potato yields to traditional methods that utilize sprinkler irrigation, without unduly affecting marketable tuber size and quality. The W80%F50% treatment (438 mm water and 50 mg N L−1) showed that this dose is sufficient for optimal potato growth in conjunction with water and fertilizer savings. Furthermore, water productivity is higher under the lower irrigation regime and, with regard to the economics of food production, farmers may benefit from these findings. Greater efficiency can be achieved with even lower irrigation doses (40%) but at the cost of utilizing a greater area. This is feasible if the availability of soils is not limiting but with the condition that this strategy has to take into account other fixed and variable costs, as well the environmental consequences of utilizing saline irrigation water.

**Author Contributions:** The study was conceived and designed by G.A. and N.L. P.T. performed the field experiment. All authors took a part in the data analysis, interpretation, and writing the paper. All authors have read and approved the final manuscript.

**Funding:** The study was funded by the Chief Scientist of the Israeli Ministry of Agriculture (857069512), the Goldinger Trust, Jewish Federation of Delaware and the Frances and Elias Margolin Trust.

**Acknowledgments:** We thank O.M. and his team from Kibbutz Yotvata for providing the agricultural facilities. We also appreciate the technical assistance and support of E.V. (Netafim LTD), Y.M., Y.S. and D.S.

**Conflicts of Interest:** The authors declare no conflict of interest.
