This study was conducted in two successive summer seasons of 1998 and 1999 on potato cv. Diamant at El-Zahraa, Dakahlia Governorate, Egypt to evaluate the effect of microbein compound (biofertilizer) and four different levels of (N+P), i.e., 45 kg N + 18.75 kg P₂O₅, 90 kg N + 37.50 kg P₂O₅, 135 kg N + 56.25 kg P₂O₅, and 180 kg N + 75 kg P₂O₅/fed., as well as to the interactions on growth, tubers yield and their components of potato plant. Moreover, the concentrations of N, P, K, nitrate and nitrite in the tubers, were also determined. Results indicated that treating seed potato tubers with microbein before planting increased the plant stand percentage at 25 and 30 DAP, vegetative growth, i.e., plant height, No. of main stems / plant, foliage fresh weight / plant (g), foliage dry weight / plant (%), total tuber yield (ton/fed.), number of tubers/plant, tuber average weight (g), tuber dry matter (%) and the concentrations of NPK in tubers, while, the concentrations of nitrate and nitrite decreased in the tuber by application of microbein during both seasons of 1998 and 1999. Plant height, foliage fresh weigh/plant,  foliage dry weight (%), total tubers yield / fed., number of tubers / plant, tuber average weight, tuber dry matter content ,%, concentrations of  N, P, K, nitrate and nitrite in the tuber increased by increasing (N+P) levels in both seasons. The interactions between microbein and (N+P) levels recorded positive effect on plant height, foliage fresh and dry weight / plant, total tubers yield, number of tubers / plant, tuber average weight, tuber dry matter  conent and the tuber contents of NPK in both seasons. On the other hand, the concentrations of nitrate and nitrite were decreased in tubers during 1998 and 1999 by treating with microbein. Generally, the results indicated that treating seed potato tubers with microbein at the rate of 10.670 kg/ton before planting in addition to (135 kg N + 56.25 kg P₂O₅)/fed. gave higher total tuber yield / fed. and lower concentration of both nitrate and nitrite in tubers as compared with the recommended dose of N and P fertilizers (180 kg N + 75 P₂O₅/fed.). Finaly, treating seed tubers with microbein before planting would decrease the required amount of (N+P) fertilizers by 25% / fed. and consequently the total cost production/fed., in addition to reduce the pollution of environment.