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 undertaken in the privet farm at Ezab Al Qasr Village, Al-Wahat Al-Dakhla, New Valleg Governorate. during the winter season of 2019-2020 and 2020-2021 to investigate the various combinations among organic manures, bio-fertilizers under mineral fertilization on the production of safe and economic potato tubers (Cara cultivar).
Sixty treatments were arranged in split plot design with 3 replicates which were the simple possible combination between 4 rates of NPK as mineral fertilization as main plot and 15 treatments of organic, bio-fertilization as sub plots.
The obtained results could be summarized as follows:
5.1. Vegetative growth parameters of potato:
The effect of various combination of organic manure and bio-fertilization under mineral fertilization as compared with 100% NPK from recommended dose on vegetative growth parameters i.e. germination %, plant height, number of stem, fresh and dry weight of potato plant foliage.
• With increasing NPK fertilization found an increase in all vegetative parameters up to 100%, the highest mean values for mentioned traits during both seasons were recorded for the plants treated with 100% NPK from recommended dose, while the lowest one were obtained from the untreated plants.
• All organic fertilization forms and bio-fertilization increased vegetative growth parameters, from the data found that organic manures as (FYM + PM) combined with Biofert (as N-fixation) realized high values of all vegetative parameters comparing with the other treatments whether in single or combined forms during both growing seasons.
• The average values of growth parameters were significantly affected due to the addition of all investigated treatments. In this connect, the highest mean values during both seasons were recorded for the plants treated with the combination of FYM + PM +biofert and 100% NPK.
5.2. Yield and its component of potato:
Yield components of potato tubers in expression of No. of tubers per plant, average tuber weight/g, specific gravity, dry matter of tubers (%) as well as total yield; (ton fed-1) and weight of (marketable, un marketable and seed-sized tuber 45-60 g) as affected by various combination of organic manure and bio-fertilization under mineral fertilization during 2019-2020 and 2020-2021.
• Using of 100% NPK was superior for recording the highest values of all the aforementioned traits, following 75% NPK, 50% and lastly 0% NPK.
• As for the effect of organic and bio-fertilization, the highest values were recorded with the treatments of FYM + PM + Biofert in two seasons, while the lowest one with bio-fertilizer in form of (potassium releasing bacteria).
•The highest mean values recorded with application of FYM + PM + Biofert in presence of 100% NPK during two seasons.
5.3. Chemical composition of potato leaves and tubers:
Chemical composition of leaves as chlorophyll content (a, b and total), N, P, K% as well as NO3-N, NO2-N ppm and starch% in potato tubers affected by various combination of organic manure and bio-fertilization under mineral fertilization and their interaction during both seasons of the experiment.
•With increasing NPK fertilization from 50 up to 100% the values increased comparing with the untreated plants, the highest values of the parameters of chemical content in leaves and tubers recorded with the treatment of 100% NPK in the two seasons.
•The highest mean value of all chemical composition during two seasons was realized for the treatment of FYM + PM + Biofert, while the lowest one realized with the treatment of Biopotass alone. On the other hand, a significantly decreases were happened in the mean values of NO3-N and NO2-N in potato tubers due to an addition of the various organic manures and bio-fertilizers. The lowest values were recorded with the treatment of Biofert alone
•Potato plants fertilized with different sources of organic manures or bio-fertilizers in solo way or combined together increased all chemical composition under all mineral fertilization comparing with the full dose NPK alone. The treatment of FYM + PM + Biofert was found to be superior for increasing the measured parameter under all mineral fertilization. In this respect, found that the highest values recorded with the treatment of FYM + PM + Biofert with 100% NPK. The same trend was true during both seasons. On the other hand, with increasing rates of mineral fertilization found an increase in NO3 and NO2 accumulation, but with addition of organic manures or bio-fertilization this accumulation decreased. This trend was true during both seasons of the experiment.