Reducing nitrogen fertiliser alters dairy shed effluent quality
DOI:
https://doi.org/10.33584/jnzg.2017.79.538Abstract
Abstract Dairy farmers using low rates of nitrogen fertiliser observed reduced odour in milking sheds, and a smaller growth response of pasture to effluent application. Effluent samples from four conventional (>100 kg N/ha/year, "high-fert") and three low-nitrogen (N) fertiliser (<50 kg N/ha/year, "low-fert") properties were collected in January 2017 and analysed for total N concentration, N form, mineral nutrient concentration and pH. Total effluent N concentration was comparable between both classes of farm. However, low-fert properties had a higher proportion of N in organic forms as opposed to ammoniacal-N than high-fert properties (mean 75% and 59% organic on low- and high-fert properties, repectively, P<0.01). Low-fert effluent also had a lower pH, higher P concentration, and nearer optimal N:P ratio than effluent from highfert properties. It was hypothesised that reducing N fertiliser may result in more nutritionally-balanced effluent (N:P ratio), causing microbes to multiply more rapidly (lowering pH), storing N in microbial biomass, reducing ammonia emissions and odour, and reducing the risk of N leaching from effluent applied to pasture. Keywords: dairy shed effluent, nitrogen fertiliser, ammonia, organic N, environmental lossDownloads
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