الفهرس 
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Abstract
Two field experiments were performed at the Experimental Station, Faculty of Agriculture, Mansoura University during two successive summer seasons of 2002 and 2003. The objective of this experiment was to study the effects of different levels of both nitrogen and phosphorus either single or in combined applications on the vegetative growth, chemical composition, yield and quality of sweet pepper fruits as well as nitrate accumulation. So, it has become essential to search for untraditional fertilizers, such as biofertilizers as substitutes or supplements for chemical fertilizers. from the results mention previously, for the first and second experiments one and two, it could be concluded that, using biofertilizer i.e. (Azotobacter chroococcum and Azosperillium lipoferum) plus different N fertilizer levels and biofertilizer (PDB + different P levels) caused a marked increase in dehydrogenase activity, vegetative growth consequently, yield and quality. It was noticed that using 105 kg N fed1 dose in combination with inoculation transplant with mixed biofertilizers (bacteria fixing nitrogen) gave as high yield of 140 kg N fed1. It was worthy to mention that the treatment of 70 and 105 kg N fed1 plus biofertilizer reduced nitrate concentration in sweet pepper as compared with the plants only treated with 140 kg N fed1. Also, it was noticed that 34.8 kg P2O5 fed1 combined with biofertilizer phosphate dissolving bacteria (PDB) gave as high yield from 46.5 kg P2O5 fed1 alone and decreased the environmental pollution. from the economical point of view, it can be recommended that 105 kg N or 34.8 kg P2O5 fed1 plus using biofertilizer was sufficient to attain the maximum and the economical fruits yield.