Distribution Characteristics of Free-living Nitrogen-fixing Bacteria in Solonetz Soil Types

Abstract

Solonetz soils, characterized by high sodium content and dense subsurface horizons, are globally distributed across arid and semi-arid regions, including parts of Central Asia, Eastern Europe, Australia, and South America. These soils pose significant challenges to agriculture due to poor structure, low permeability, and limited nutrient availability. Their high exchangeable sodium percentage negatively affects root growth and water infiltration, reducing crop productivity. Despite these constraints, understanding Solonetz soil dynamics is crucial for land reclamation and sustainable agriculture. This study investigates the solonetz soil type of Eastern Georgia, characterized by a pH of 6.42, moisture content of 12%, Salinity -0.8% , and a hydrolyzable nitrogen content of 5.2 mg per 100 g of soil. The study determined the population and genera composition of free-living nitrogen-fixing bacteria per gram of dry soil: Azotobacter (865,155; 22.27%), Beijerinckia (275,167; 7.08%), Azospirillum (2,678,150; 68.94%), and Derxia (65,750; 1.69%). Azospirillum was found to dominate, which correlates with low hydrolyzable nitrogen levels. The results suggest a probable link between the concentration of easily hydrolyzable nitrogen in soil and the distribution of nitrogen-fixing bacteria.