This study was conducted during 2016 & 2017 seasons on 13-year-old Washington navel orange
trees budded on Sour orange rootstock planted at 5 x 5 meters apart under surface irrigation in a private orchard
at Manzala village, Toukh region, Qalubia Governorate, Egypt. The main goal of this investigation was directed
towards increasing Washington navel orange trees growth, nutritional status, productivity and fruit quality
associated with lowering its production cost through minimizing of chemical NPK fertilizers by granulated
organic NPK, natural raw rocky materials and biofertilizers. The experiment included seven treatments; T1-100%
of chemical NPK, T2 - 100% of natural alternative NPK fertilizations mixture, T3 - 100% of NPK bio-fertilizations
mixture, T4– 50% of NPK bio-fertilizations mixture + 50% of natural alternative NPK fertilizations mixture.,
T5 - 50% of chemical NPK + 50% of natural alternative NPK fertilizations mixture, T6 - 50% of chemical NPK +
50% of NPK bio-fertilizations mixture and T7- 33.3% of chemical NPK + 33.3% of NPK bio-fertilizations mixture
+ 33.3% of natural alternative NPK fertilizations mixture. Obtained results revealed that all investigated
treatments increased growth parameters (number, length, thickness of developed shoots, number of leaves/each
and leaf area), as well as total leaf chlorophyll and nutritional status (leaf N, P, K, Ca, Mg, Fe, Mn and Zn) and
positively responded fruit (set% and retention%), yield/tree and fruit quality were also improved. However,
T1-100% of chemical NPK and T7- 33.3% of chemical NPK + 33.3% of NPK bio-fertilizations mixture + 33.3% of
natural alternative NPK fertilizations mixture were statistically the superior. Moreover, T6 - 50% of chemical
NPK + 50% of NPK bio-fertilizations mixture ranked statistically second in this concern.