The Effect of Mineral and Biological Nitrogen on Microbiological Traits of Smonitza and Maize Yield

Abstract

The paper presents the study on the effect of inoculation of maize seed (NSSC-640) by asymbiotic nitrogen-fixing bacteria (Azotobacter chroococcum, strain 84) and increasing rates of mineral nitrogen on quantitative composition of microorganisms (total number of bacteria, number of actionomycetes and azotobacter) in smonitza under maize and on the yield of the grown crop. The following fertilization treatments were studied: N1PK (90:75:60 kg/ha'); N2PK (120:75:60 kg/ha'); NJPK (150:75:60 kg/ha'), as well as the treatment with presowing inoculation of maize seed. Microbiological analysis included the assessment of total number of microorganisms, actinomycetes and azotobacters in the rhizosphere and edaphosphere during maize vegetation. Total numbers of microorganisms were determined by growth on the medium for the total number with an appropriate amount (0.5 ml) of 10-6 soil dilution, numbers of actinomycetes - by growing on synthetic agar according to Krasil 'nikov with 10-4 of soil dilution and azotobacters - by growing on Fyodorov's agar with 10-2 of soil dilution. The study results showed that the numbers of microorganism groups were affected by the type and rate of fertilizers applied, as well as by the time and sampling zone. The application of Azotobacter chroococcum, strain 84, resulted in an increase of the total numbers of microorganisms, actinomycetes and azotobacters, especially in the rhizosphere soil at the onset, and even in the middle of maize vegetation. Lower rates of nitrogen fertilizers (90 and 120 kg/ha') led to a significant increase of total bacteria numbers, as well as an insignificant change in azotobacter numbers, whereas their high rate (150 kg/ha') had a depressive effect on the mentioned microorganisms, paricularly in the edaphosphere of maize. In contrast, actinomycete numbers were not reduced even with this nitrogen treatment. Under the studied agroecological conditions, the highest maize yield, but not economically justified one, was obtained with the highest nitrogen rate. Seed inoculation with Azotobacter chroococcum, strain 84, caused an insignificant rise in maize yield, which can be associated with acid reaction of the soil studied and slower release of nitrogen accumulated in their cells.