THE EFFECT OF ADDITION SOME ORGANIC MATTERS IN BIOLOGICAL OXIDATION OF AGRICULTURAL SULFUR AT DEFERENT LEVELS OF SOIL COMPACTION. П.-Population densities of autotrophic and heterotrophic sulfur oxidizing Microorganisms

Abstract

This study was conducted to evaluate the interaction effect of different levels of agricultural sulfur, organic matter source and compaction on the biological oxidation of sulfur, through studying the variation in population densities of autotrophic and heterotrophic sulfur oxidizing microorganisms during different incubation periods. A factorial experiment was conducted according to a complete randomization design with three replicates., to know the effect of three agricultural sulfur levels (0 , 1 and 2) gm Sº. kg-1 soil (S0 , S1 and S2) respectively, with three organic matter treatments those without organic matter, addition of dried alfalfa and cow manure which added in one level 6 gm C. kg-1 soil (C0 , C1 and C2) respectively. Soil compacted to reach three levels of bulk density 1.25 , 1.35 and 1.45 Mg. m-3 (B1 , B2 and B3) respectively. All the treatments was incubated at 28± 2◦C for 15 , 30 and 45 days (T1 , T2 and T3) respectively with maintenance the soil moisture content for all treatments at 50% of the available water by weight method,: Through every incubation period the population density of autotrophic and heterotrophic sulfur oxidizing microorganisms were evaluated by M.P.N. method. The results obtained from this study could be summarized as follows: 1- population density of both autotrophic and hetrotrophic sulfur oxidizers differently affected by sulfur, organic source and compaction treatments. The higher average counts of the autotrophes were (16.58 , 30.33 and 11.1 x 102 cells. g-1 dry soil were recorded under treatments S1 , C1 and B2 respectively, while those of the hetrotrophies (6.29 , 7.62 and 5.55) x 107 cells. g -1 dry soil were found in S0 , C2 and B2 treatments. Respectively. 2- Generally, The interaction treatments showed the highest values at (S1C1B2) treatment after 30 days of incubation (T2). population densities of autotrophic and heterotrophic S-oxidizers recorded under this treatment were 7.98 x 102 and 7.98 x 107 cells. g-1 dry soil, respectively.