Effect of inoculation with phosphate-bacteria, sawdust compost and nitrogen sources on okra yield and some properties of calcareous soil

Two pot experiments were carried out during the seasons of 1999 and 2000 at Agricultural Research Center in Giza using a calcareous soil media to investigate the effect of phosphate dissolving bacteria (PDB) inoculation, sawdust compost and different nitrogen sources on growth and yield of okra plants. Moreover, the changes in some biological and chemical properties of the used soil after 175 days of planting were also recorded. Bacillus megatherium var phosphaticum was used as inoculum at the time of planting. While, two rates from sawdust compost were used, i.e. 2.5% and 5% in addition to the control treatment. The nitrogen fertilizer was added at four sources namely, (B) nitric acid solution (0.1 (N) under bar), (C) nitric acid- calcium nitrate (1:1) mixture, (D) calcium nitrate solution and (E) urea solution on nitrogen basis compared with no mineral nitrogen application (A). The obtained results indicate that, inoculation of okra plants with PDB and addition of sawdust compost significantly increased plant growth, fruits yield and nutrients uptake. The highest increments of this parameter were achieved under used higher compost rate (5%) than 2.5%. The obtained results show also that, nitrogen fertilization was very important to okra plants in such soil regardless the form of added nitrogen. On the other hand, the completely and partially acidic nitrogen form induced a positive effect on the availability of nutrients such as P and K which is reflected on uptake by plant fruits. Viable microbial counts, phosphate dissolving bacteria and dehydrogenase activity in the soil as well as the availability of mineral N, P and K were enhanced by organic manuring and inoculation with PDB. Moreover, the addition of organic manure increased the organic matter percentage in the soil and lead to a slight decrease in its pH value. Therefore, adding sawdust compost to a calcareous soil in presence of acidic nitrogen fertilizer form as well as PDB inoculation could be recommended to obtain the best results for okra fruits yield and favorable nutrients uptake.