Biogeochemical cycling bacterial activity in response to lime and fertilizer applications in pond systems

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Lime-induced changes of biogeochemical cycling bacteria were examined using doses of 25, 50, 100, 200, 500, 1000 and 2000 kg ha−1 in the first part, and post-lime inorganic and organic fertilization in the second part of the experiment. Heterotrophic, ammonifying, denitrifying, cellulose decomposing and phosphate solublizing bacteria were drastically reduced by 30–90% in 1000 kg ha 21and 51D91% in 2000 kg ha−1. Density differences were minor in the remaining test doses for all groups of bacteria except for the dinitrifiers which were reduced in 500 kg ha−1 by 90% over the control. Similarly, reduced rates of ammonification, nitrification and denitrification were dose-dependent. Inorganic fertilization following lime application of 2000 kg ha−1 resulted in no marked increment of the counts of bacteria and activity processes, whereas organic manuring increased the density (50–200%) and the activities (212–292%) as well. Lime-induced changes of bacterial population and activities were explained as a result of high pH stress as well as a major shift in the CO2-HCO3-CO3 equilibrium system. Increase of major nutrients in the post-lime organic treatment was significantly higher than that of inorganic fertilization resulting in favourable N/P ratio and water quality conducive to fish farming after 45 days of liming.