Ammonia-Oxidizing Bacteria Populations and Activities in Soils Irrigated with Municipal Waste Water Effluent
1982
Chopp, K. M. | Clapp, C. E. | Schmidt, E. L.
Land application of waste water when properly managed has the beneficial result of providing nutrients and water to crops without adverse environmental effects. Populations and activities of NH₃-oxidizing bacteria were studied during one growing season of corn (Zea mays L.) on soil irrigated with municipal waste-water effluent. The method used to recover these bacteria from soil was shaking 1 hour in Soriano-Walker medium. Soil populations of one serotype each of the genera Nitrosomonas, Nitrosolobus, and Nitrosospira were enumerated by the fluorescent antibody (FA) technique. Populations of the three genera peaked at different times, with “total FA-detectable” populations fluctuating only slightly over the entire season. Higher effluent (220 cm, 470 kg N/ha) treatments tended to have slightly lower populations than either fertilized control (336 kg N/ha) or low effluent (120 cm, 250 kg N/ha) treatments. Ammonia-oxidation activity was significantly (5% level) higher for soils treated with high rates of effluent. Soil N levels showed NH₄-N decreasing sharply when the population of NH₃-oxidizers peaked in June, but accumulating in the fall when populations declined. Concentrations of NO₃-N in soil were directly related to effluent and fertilizer applications. Nitrate concentrations in soil water and ground water peaked approximately 1 month after the maximum NO₃-N concentrations occurred in the soil.
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