Selected Extracellular Soil Enzymes As Impacted By Long-Term Applications of Manure.

Extracellular soil enzymes are involved in numerous biogeochemical processes impacting soil organic matter transformations and nutrient cycling. The present study aimed to evaluate soil enzyme activities as influenced by 10 yr of different manure application rates and times applied to a  timothy crop at two sites having different soil textures; i) silt clay loam (Dykeland site), and sandy loam (Upland site). Manure was applied in spring, summer, early fall (August-September) and late fall (October-November) at 0, 75, 150 and 300 total kg N ha^-1. Beta-glucosidase (BG), cellobihyrdolase (CB), acid phosphomonoesterase (PHOSPHO), and Leucine aminopepdtidase (LAP) were determined on soil samples taken in fall after 10 yr of manure application. Enzymes were quantified using fluorimetric method. Manure application rate effect was significant on all tested enzymes showing quadratic trends with the control showing significantly lower values than other rates. Site effect was significant on PHOSPHO with higher values associated with Dykeland site, and on LAP with higher values at Upland site.  Time application effect was only significant on PHOSPHO with late fall application and summer application showing higher and comparable values than spring and early fall applications. The results support the hypothesis that the function and structure of soil microbial community that controls soil enzyme activities can be impacted by fertilisation management and soil type.

Key words: extracellular soil enzymes, Beta-glucosidase, cellobihyrdolase, acid phosphomonoesterase, Leucine aminopepdtidase,  fluorimetric assay.