Individual study: Rapid changes in microbial biomass and aggregate size distribution in response to changes in organic matter management in grass pasture
Hurisso T.T., Davis J.G., Brummer J.E., Stromberger M.E., Mikha M.M., Haddix M.L., Booher M.R. & Paul E.A. (2013) Rapid changes in microbial biomass and aggregate size distribution in response to changes in organic matter management in grass pasture. Geoderma, 193-194, 68-75
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Amend the soil with manures and agricultural composts
A controlled, replicated experiment in 2009 on loamy soil in Colorado, USA (Hurisso et al. 2013), found higher soil microbial biomass under high levels of composted dairy manure (239 μg C/g soil, 80.8 μg N/g soil) or an alfalfa Medicago sativa crop (277 μg C/g soil, 90.9 μg N/g soil) when added to grass pasture, compared to medium (158 μg C/g soil, 38 μg N/g soil), low (144 μg C/g soil, 38 μg N/g soil) or no additions (157 μg C/g soil, 29.3 μg N/g soil). There were three replicates (in 3 x 12 m plots) of four treatments: composted dairy manure applied at low (22.4 Mg/ha), medium (33.6 Mg/ha) and high rates (44.8 Mg/ha), and alfalfa interseeded into the grass mixture (including orchardgrass Dactylis glomerata, meadow brome Bromus biebersteinii, and smooth brome B. inermis). Soil samples were taken up to 15 cm depth after roughly 1.5 years, and measured soil microbial biomass (levels of carbon and nitrogen) and the size of accumulated soil particles.