THE PRESENT work aimed at throwing some light on the possibility of substituting, partially, the amount required of mineral nitrogen for fertilization of a certain crop by organic manuring and biofertilization. Such an investigation would provide knowledge about to what extent these substitutes can replace mineral nitrogen fertilizer and how far they can affect the percentage of fertilizer N recovery (% FNR) by maize plant (Zea nieys) grown on an alluvial soil from Moshtohor and a calcareous one from El- Noubaria. An additional desired environmental goal can be achieved through minimizing pollution of soil with mineral nitrogen and hence reducing us release to groundwater or surface water. Approaching the aimed goals was executed through performing a factorial pot experiment in a randomized complete block design with three replicates. Rates of N ranging from 0 to 90 mg N kg"' were tried through different combinations between ammonium sulfate labeled with N15 (AS) and chicken manure (CM). Soil pots (5 kg each), received basic supplements of P (as rock phosphate) at 100 mg P kg"' and K (as K2SO4) at 50 mg K kg"1 and micronutrients in a Hogland solution. The pots were sown with either uninoculated maize grains or maize grains inoculated with either Azotobncter chroeoccum (Azt), Azospirillitm brasilensc (Azs) or both bacteria together immediately before seeding and left to grow for 60 days. Application of nitrogen in a mineral form or an organic one or in a combination of both the forms increased dry weight of plant and its uptake of N. The inoculated treatments showed higher values than the uninoculated ones, combined application of (Azt +v Azs) was more effective than inoculation with either alone. % FNR of the treatments that received combined inoculation were higher than the corresponding ones that received single inoculation with either Azt or Azs, inoculation with Azt seemed more effective than that with Azs, activity of N2- fixing bacteria was more obvious at rates of applied N less than 30 mg N kg"1 beyond which activity of N2- fixing bacteria decreased. The alluvial soil gave higher dry weight and N uptake than the calcareous one. Biofertilization through inoculation with Azt or Azs as well as applying organic manure could minimize the dose of mineral N required to be applied which is a profitable from the economic point of view and effective in reducing pollution of soil with N. |
