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Diverse crop rotations, cover crops and the possibility of integrating livestock make organic systems potentially more sustainable than other agroecosystems. Lower reactive N in organic systems minimizes the potential for N losses. However, addition of organic manures and residues containing mineralizable N and C have the potential to enhance nitrous oxide emissions. We conducted a 39 d laboratory incubation to assess key microbiological drivers controlling nitrification and denitrification from two annual organic vegetable systems receiving 1) mixed-compost, or 2) broiler litter and 3) an organic perennial pasture system.
Ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) abundance, amoA gene copies as biological indicators of soil health in different treated organic systems. Statistical significant differences (univariate one-way ANOVA in PROC GLM, post hoc: Fischer LSD) are indicated by different letters (lower case for AOA abundance; upper case for AOB abundance).
Ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) population, amoA gene copies as influenced by multiple freeze-thaw events. Pre-freeze sampling time point 13 d at 3 °C; 1st Freeze-thaw sampling time point 31 d (freeze at -3 °C, thaw 4 °C); 2nd Freeze-thaw sampling time point d 39 (freeze at -2 °C, thaw 4 °C). Statistical significant differences (univariate one-way ANOVA in PROC GLM, post hoc: Fischer LSD) are indicated by different letters (lower case for AOA abundance; upper case for AOB abundance).
We found that archaeal (AOA) and bacterial (AOB) nitrifier amoA gene copies were affected by temperature, reactive N species and long term management during multiple freeze-thaw cycles. They could potentially serve as biological indicators of soil health revealing useful information about biogeochemical processes and losses of reactive N. (Bhowmik et al 2016; Soil Biology & Biochemistry).
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