الفهرس 
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Abstract
This study was performed to reducing mineral fertilizers and replacement of natural and bio fertilizers instead of it on the vegetative growth, nutritional status, productivity of potato plants and quality of tubers. The experiments were conducted at Giza Agriculture Research Station, Giza Governorate, Egypt. Potato tubers of (Lady Rosetta and Lady Balfour cultivars) were sowing in clay soil during summer season at the third week of January 2016 and 2017 seasons. Plants were irrigated using a surface irrigation system. Single or mixed phosphate rock agents with Bacillus megaterium and feldspar with Bacillus circulans were used in the presence of either, mineral nitrogen or compost with Azotobacter chroococcum + Azospirillium brasilense. The effect of these parameters on growth characteristics and yield components was compared to the recommended dose of nitrogen, phosphorus and potassium as a mineral fertilizers.
The experimental soil was ploughed and divided into ridges (70 cm width). The tubers were sown at a distance of 20 cm on one side of ridge. The plot area was 10.5 m2 (3 m length and 3.5 m width). Each plot included 5 ridges.
In regard the interactions between cultivars and fertilizer treatments, Lady Balfour cultivar when fertilized with application of mineral N + rocks of PK + P dissolving and K releasing bacteria gave the highest gross and net return.
It could be concluded that, rock phosphate and feldspar with phosphate dissolving bacteria and K releasing bacteria could be an alternatives to mineral PK for similar tubers yield of potatoes, as well as obtain the highest net return. While, compost with N fixing bacteria could be an alternative to mineral N for slightly low yield of potatoes but it’s distinguished by high quality and healthy with a low content of nitrate.