Monday, November 5, 2007 - 10:00 AM
95-3

Cow Urine and Soil Moisture Effects on Soil Chemistry and Microbial Communities.

Janet E. Bertram1, Kate H. Orwin2, Tim J. Clough1, Leo M. Condron1, Robert R. Sherlock1, and Maureen O'Callaghan3. (1) Soil and Physical Sciences, Lincoln University, P O Box 84, Lincoln University, 7647, New Zealand, (2) Biological Sciences, Lancaster University, Lancaster, LA1 4YQ, United Kingdom, (3) AgResearch, Lincoln, New Zealand

Pastoral agriculture is the mainstay of New Zealand’s economy, and for several decades dairy farming has been undergoing rapid expansion. Dairy farming practices in New Zealand generally entail cattle grazing year-round in open pastures, so that wastes are returned directly to the land. Bovine urine deposition is known to alter soil physical and chemical conditions (e.g. increased pH and ionic concentrations). However, little research has been carried out on the effects of urine on soil microbial communities.

This laboratory experiment involved the application of cow urine to repacked soil cores. The experimental design was a 2 x 3 factorial, with 2 levels of soil moisture and 3 levels of urinary salt content. The cores were maintained at either high or low soil moisture contents, and the urine treatments were no urine, low salt urine or high salt urine. Over 44 days soil cores were destructively sampled, and a number of chemical and microbiological analyses were carried out. Dehydrogenase enzyme activity and phospholipid fatty acids (PLFA) were the microbiological variables measured. These results were then compared with the chemical measurements to indicate interactions between soil chemical changes and soil microbial changes after urine application.  Distinct differences between treatments for both urine and soil moisture variables were observed for chemical parameters including pH, inorganic nitrogen and dissolved organic carbon (DOC). Dehydrogenase activity and PLFA analyses also showed microbiological changes due to the moisture and urine treatments.