TITLE:
The Effect of Grassland Management History on Soil Carbon Response to Slurry and Urea
AUTHORS:
Junfang Cui, Nicholas M. Holden
KEYWORDS:
Soil Carbon, Management History, Slurry, Urea, Enzyme
JOURNAL NAME:
Open Access Library Journal,
Vol.4 No.11,
November
17,
2017
ABSTRACT: Slurry and urea applications are part of normal nutrient management on grassland farms utilizing grazed grass and silage for animal production. It was hypothesized that management history would result in a different carbon response to slurry and urea applications for the same soil type because of differences in soil micro-environment, including microbial biomass and activity, are formed and regulated by long-term management history. An Irish grassland soil of the Skeagh Series was sampled in three fields, each with a long, consistent management history: Soil A was associated with extensive grazing by horses; soil B with medium intensity grazing by sheep and cattle, and grass silage conservation; and soil C with intensive dairy cow grazing. There were three slurry treatments (S1, the control of no slurry; S2, slurry mixed with soil; S3, slurry added on the soil surface) and three urea treatments (N1, the control of no urea; N2, all urea applied at one time; and N3, three application, 30 days apart, totaling the same amount of urea as N2) designed to supply 36 g C m﹣2 and 2 g N m﹣2 during an 85 day incubation trial. Soil pH, total carbon, cold water extractable organic carbon, soil respiration and two C-related enzymes (β-glucosidase and CM-cellulase) were measured. All measured soil properties showed a significant difference (P β-glucosidase and CM-cellulase activity showed a strong relationship with soil management history rather than with slurry or urea additions. It was concluded that management history was important to C dynamics. Slurry mixed with soil resulted in a greater soil carbon loss than slurry applied on the soil surface. One large dose of urea caused greater soil carbon loss than multiple small doses.