Effect of nitrogen mineral fertilisers on crop inoculation efficiency with use of associative and symbiotic nitrogen fixers

Abstract

High efficiency of pea inoculation with symbiotic bacteria complex Rhizobium leguminosarum and diazotrophs Klebsiella planticola and Pseudomonas sp. was first determined. Similar inoculation with bacteria complex was found to be effective twice the high mineral nitrogen rate (80k g/ha), thereby contributing to a better utilisation of soil and atmospheric nitrogen by pea and, subsequently, to a higher yield and higher N quantity. The complex of bacteria Rhizobium leguminosarum + Klebsiella planticola decreased nitrates amounts in the soil, whereas that of Rhizobium leguminosarum + Pseudomonas sp. caused their increase. Complex inoculation Rhizobium leguminosarum + Klebsiella planticola and Rhizobium leguminosarum + Pseudomonas sp. didn't visibly change absorption (¹⁵NH₄)₂SO₄ by plants, indicating neither the accumulation of ¹⁵SN stable isotope in the plants nor the presence of N which had been fixed by bacteria in the structure of peayield.