The efficiency of biogas digestate on grassland compared to mineral fertilizer and cattle slurry
2014
Tampere, M., Estonian Univ. of Life Sciences, Tartu (Estonia) | Viiralt, R., Estonian Univ. of Life Sciences, Tartu (Estonia)
Biogas production from organic wastes is gaining popularity, especially in agriculture, which produces high quantities of organic wastes suitable for anaerobic digestion. Digestate is the valuable by-product of the biogas production that is considered as a valuable fertilizer. The objectives of the experiment conducted from 2012 to 2013 at the Estonian University of Life Sciences were to compare the impact of biogas digestate, undigested (raw) cattle slurry, and inorganic nitrogen fertilizer on grass yield and to assess the fertilizer value of digestate produced from different feedstock. Fertilizers were applied to the grassland rich in low grasses by broadcasting in quantities according to the nitrogen rate of 180 kg haE-1 in three split applications. The application rate of organic fertilizers was calculated based on NH4 -N content. Grassland yield was determined on four treatments: (i) control (no fertilizer was applied), (ii) mineral N-fertilizer (NH4 NO3), (iii) cattle slurry and (iv) cattle slurry digestate. Grass yield was measured three times during the growing period. Our research showed that digestate when applied based on its NH4 -N content is effective fertilizer in grassland. It could be used as a substitute for mineral-N fertilizer, but its efficiency is slightly lower when compared to cattle slurry, due to its lower application amount resulting in lower nutrient and organic matter amount applied to the grassland. Co-digestion of cattle slurry with solid manure, hay and silage does not decrease digestate fertilizer value in grassland, because the addition of other substrate increases digestate DM content.
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