This study was performed to evaluate the application of humic substances with either single or combined N, P and K fertilizers through drip irrigation system on availability of NPK nutrients at 0-15, 15-30 and 30-45cm soil layers, tuber quantity, quality and nutritional status of fertigated potato grown on sandy soils. So, field experiment was carried out at the experimental farm of the Agricultural Research Station, National Research Centre, El-Nubaria district, Egypt during the summer of 2008 season. The experiment was set up in split plot design with three replicates, main treatments were assigned fertilizer types, ie single and combined fertilizers, while sub treatments were presented 4 treatments as follow, 100% of recommended chemical N, P and K fertilizer doses (control) and humic substances was injected with 100, 75 and 50% of N, P and K fertilizers through drip irrigation system. Data revealed that fertigation of combined NPK fertilizer was more efficient than single N, P and K fertilizers on improving tuber yield quantity, quality indicators and nutritional status of potato crop, as well as soil fertility after harvesting at all soil layers. Additional rates of fertigation significantly increased the tuber yields, tuber quality indicators, NPK nutrient concentrations in potato tissues and fertilizer use efficiency (kg yield kgG NPK fertilizer) except for specific gravity (g cm) and TSS (%) in tubers. Moreover, humic 1-3 substances added with NPK fertigation treatments resulted in lesser leaching N, K to deeper layer and higher available P to deeper layer of soil. Also, the tuber yield was increased by 16.47% with addition of humic substances comparing to the recommended rate solely. The most considered treatments for enhancing tuber yield, quality indicators, nutritional status of potato crop and soil fertility compared to the recommended dose of N, P and K (control) was addition humic substances with 100% fertigation followed by 75% fertigation of combined NPK fertilizer with slightly difference between such two treatments. There is a parallel trend was observed between the addition of humic substances with 75% fertigation treatment of combined NPK fertilizer and the addition of 100% fertigation treatment solely (recommended rate).