Two field experiments were carried out at the Vegetable Crops Farm in Baramoon Research Station, Dakahlia governorate, Egypt, during the two winter seasons, to investigate the effect of irrigation intervals under different sources of potassium combined with foliar application nano-K fertilizer on plant growth and productivity of garlic cv.Sids 40. The experiment includes 42 treatments which arranged in strip-split block design, as the interactions between three irrigation intervals (14, 21 and 28 days) as vertical plots, seven sources of potassium fertilization (100% K-mineral (150 kg Potassium Sulphate/fed.), 100% K-biofertilizer (2 L/fed., PSDB, Bacillus circulans), 100 % K-natural (700 kg Feldspar/fed.), 50 % K- mineral (75 kg/fed.) +50 % K-natural (350 kg/fed.), 50 % K- mineral (75 kg/fed.)+inoculated by PSDB, 50 % K-natural (350 kg/fed.)+inoculated by PSDB, and 33% K- mineral (50 kg/fed.)+33% K-natural (235 kg/fed.)+inoculated by PSDB as horizontal plots and two foliar applications (with nano-K and without) as split plots. Obtained results indicated that, the fertilization of plants with different sources of potassium as 33% K-mineral (50kg/fed.)+33% K-natural (235 kg/fed.) combined with inoculated by PSDB (2 L/fed), showed the best vegetative growth parameters and the highest yield productivity followed by the treatment of 50% K- mineral+50 % K-natural combined with foliar application by 3000 ppm nano-K particles under irrigation every 21 days Therefore, we recommend this treatment because it saves in the amount of mineral potassium and the amount of irrigation water and thus reduces the costs of garlic production and environmental pollution under the same conditions.