IMPROVING THE EFFICIENCY OF INORGANIC PHOSPHORUS AS AFFECTED BY PHOSPHATE DISSOLVING BACTERIA UNDER CALCAREOUS SOILS

Abstract

A filed experiment in split-split plot design was conducted on acalcareous soil at Nubaria Agriculture Research Station, El-BeheraGovernorate, Egypt, during the growing seasons of 2012/2013 and2013/2014 to study the effectiveness of seed inoculation by Bacillusmegaterium (as a phosphate dissolving bacteria (PDB)) on enhancementthe P availability and improvement use efficiency of many inorganicphosphorus forms and rates in soil to improve the production of fababean (Vicia faba L.) cultivar sakha 4 . Three fertilizer P forms namelyP1; single super phosphate 15.5% P2O5 (SSP), P2; triple super phosphate46% P2O5(TSP) and P3; phosphoric acid (H3PO4) 72.4% P2O5 (PA), at75% and 100% of recommended doses (45 kg P2O5 fed-1 RD).The results revealed that PDB inoculation increased theirpopulation in soil and significantly increased the availability of P incalcareous soil whether applied alone or combined with added P formscompared without it, where the treatments of TSP at 75 and 100% RDcombined with PDB gave the highest percentage (125.8, 136.4%) at the50 days age and the lowest percentage (50.9, 53.3%) at harvest,respectively. The results indicated to increase macronutrients uptake byfaba bean plants, which positively reflected on quantities and qualities ofyields. It can be concluded that adding TSP at 75% RD combined withPDB inoculation is the recommended for improving the productivity offaba bean crop, while the means values of seed yield relatively increasedabout with 41.4% over the same treatment without PDB and about 34.2,36.9% for PDB inoculation and TSP forms as individual effectrespectively. It was noticed that the PDB-inoculated seeds increasedphosphorus use efficiency (PUE), phosphorus agronomic efficiency(PAE) and phosphorus recovery efficiency (PRE) by about 33.04, 101.1and 138.1%, respectively over the uninoculated. Triple superphosphate(TSP) has the greater efficiency whether it was alone or combined withPDB inoculation at 75% RD addition compared to other forms.