The effect of different kinds of fertilizers on the number of Azotobacters in the Smonitza type of soil under maize and the yield of maize

Abstract

Lower nitrogen rates stimulated the development of Azotobacters in the soil during almost the entire investigation period. Solid barnyard manure exerted a similar effect. Liquid manure had a somewhat shorter active impact on the growth of Azotobacters. High nitrogen rates had a non-stimulating effect on the investigated group of microorganisms, particularly in the initial growing stages and in the period of low soil humidity (mid vegetation). The toxic effect of high nitrogen rates was considerably lower in the rhizospheric soil, as well as in the periods of increased humidity.

The most significant increase of the yield of maize silage during the first research year was obtained by the medium nitrogen rate (120 kg ha^-1), whereas in the other years, a higher yield of maize silage and grain in the variant with 150 kg N ha^-1 was statistically insignificant. Except for the first, in the two following investigation years the organic fertilizers did not significantly increase the yield of maize silage and grain. The application of Azotobacter strain resulted in the statistically insignificant increase of the mentioned productive traits of this field crop.