INPACT OF SWINE MANURE ON BACTERIA TRANSPORT THROUGH UNDISTURBED SOIL COLUMNS

Abstract

Land application method of animal manure can have a significant effect on theleaching of bacteria to ground water. In order to determine the effects of manure placementmethod and application rate on bacteria transport with subsurface water, a soil column studywas conducted in the laboratory in the spring of 2000. A total of 20 undisturbed soilcolumns were collected from a no-till corn field. Liquid swine manure was applied to thesecolumns at two application rates (to give N application rate of 336 kg-N/ha and 168 kg-N/ha)using broadcast and incorporated methods of application. Three simulated rainfall amountswere applied on these soil columns using rainfall intensities of either 6.35 cm/hr (2.5 in/hr) or0.762 cm/hr (0.3 in/hr). Fecal streptococcus and E-coli bacteria concentrations in theleachate were determined for all three simulated rainfall events. The results of this studyindicated that broadcast method of manure application resulted in higher bacteriaconcentrations in the leachate in comparison with incorporated method. A positivecorrelation existed between the manure application rate and bacteria concentrations in theleachate, but differences in bacteria concentration were not statistically significant at 5%level between two application rates. Highest bacteria concentrations in the leachate wereobserved from columns receiving manure at a higher application rate using broadcast methodof application.<br><br>Results of this study suggest that bacteria transport to subsurface drainage water,under no-till conditions, is affected by the method and rate of manure application, soilstructure, and rainfall intensity. Presence of large number of macropores in the undisturbedsoil columns may be one of the reasons for higher bacteria concentrations in the subsurfacedrainage water under surface broadcast method of manure application. Incorporating ofliquid manure in the surface 5 to 10 cm soil layer disturbed macropores resulting in lowerbacteria concentration in the leachate.