الفهرس 
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Abstract
The excessive use of inorganic fertilizers, especially N, P and K represents the major cost in plant production and creates pollution of agro ecosystem as well as deterioration of soil fertility. Under these circumstances, supplementing or substitution of inorganic fertilizers with organic sources, particularly those of microbial origin is needed. So the present investigation was carried out to investigate the possibility of partial or complete substituting chemical fertilizers by bio fertilizer or organic manure or both of them for producing the highest safe yield of potato crops.Two field experiments were conducted in a loam soil at the private Farm of El-Gamalia Dakahlia Governorate, Egypt during the winter seasons of 2014 and 2015 to study the effect of the various combinations among organic manures, bio-fertilizers and mineral fertilization on the production of safe and economic potato tubers spunta cultivar.Twenty-four treatments were arranged in split – split block design with 3 replicates, which were the simple possible combination between two sources of organic manure [Farmyard manure (FYM) and compost] as main plots, three treatments of mineral fertilization (50, 75, and 100% NPK from recommended doses) as sub plots and three sources of bio fertilization (EM, yeast extract , mixture of multi strains and 0) as sub-sub plot. Thus, the total numbers of every experiment were 72 experimental units.The plot area was 10.5 m2, which contained three rows, 5m long and 0.7 m .The mean values of plant height, number of leaves/plant, fresh and dry weights and leaf area of potato plants were significantly affected due to adding FYM (20 m3 fed-1) and compost (15 m3 fed-1) during both seasons of the experimentation. The highest mean values of traits were recorded with adding compost.The effect of adding bio-fertilization treatments of EM, yeast extract and mixture on all growth parameters were significant as compared to the untreated plants. the highest significant values of the a formentioned parameters were recorded with soil fertilization by mixture of cells (2 ml/plant.) followed by soil addition EM (2 ml/l).Fresh, dry weights, number of tuber and total yield of potato ton fed-1 were positively affected due to an addition of 15 m3 fed-1 compost and recorded higher magnitudes of these parameters than the addition of 20 m3 fed-1 FYM.The mean values of fresh, dry weight, number of tuber and total yield of potato ton fed-1 were significantly increased as the level of NPK-applied was increased from 0 to 75% RD then decreased with adding 100% NPK (RD).The application of 15 m3 fed-1 from compost gave the highest values of N, P and K percentages as compared to 20 m3 fed-1 of FYM.The highest mean values for N, P and K concentrations in plant foliage after 70 days and tubers after 70 and 110 days were found to be associated with the addition of 75% RD-NPK.Adding compost at 15 m3 fed-1 reflect the highest values of chlorophyll a, b and total in the leaves of potato followed by FYM at 20 m3 fed-1 during both seasons of 2014 and 2015.Application of 75 % RD NPK fertilization led to significantly increasing the average values of chlorophyll a, b and total in the leaves of potato plant.The highest mean values of nitrite and nitrate of tuber after 70 and 110 days were recorded at the rate 20 m3 fed-1 of FYM.Application of NPK-fertilization at the rate of 100% RD was superior for increasing the average values of NO2-N and NO3-N, in tubers after 70 and 110 days compared with the other treatments.The effect of adding organic manure as compost on R.sugars, N-R sugars, total sugar percentages after 70 and 110 days were significantly increased with adding compost at 15 m3 fed-1 . R.sugars, N-R sugars, total sugar percentages after 70 and 110 days were significantly increased due to increasing NPK-fertilization rate from 50 up to 75% of the RD during both of seasons.Average values of Starch%, Vit.C mg 100g-1 and TSS% after 70 and 110 days during both seasons for the plants treated with organic manure were significantly increased with using 15 m3 fed-1 compost.Starch percentage, Vit. C mg 100g-1 and TSS% after 70 and 110 days were significantly increased due to increasing the rate of NPK-applied from 50 to 75 % RD.from obtained results , it could be concluded that treating potato plants with the mixture of microorganisms in the presence of organic manures as compost 15 m3 fed-1 and NPK at 75% recommended dose gave the highest values of all characteristics under study. Thus, it could be recommended that treating potato plants with the mixture of multi strains inoculants combined with compost rice straw at rate of 15 m3 fed-1 and the addition of 75% recommended dose from NPK considered as the most suitable treatment for realizing the highest economic and safe yield of potato tubers.