1 Section for Crop Sciences, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet2 Bioforsk, Norwegian Institute for Agricultural and Environmental Research, Organic Food and Farming Division3 Bioforsk, Norwegian Institute for Agricultural and Environmental Research, Grassland and Forage Crops Division4 Norwegian University of Life Sciences5 Bioforsk, Norwegian Institute for Agricultural and Environmental Research, Arable Crops Division6 Norwegian University of Life Sciences7 Section for Crop Sciences, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet
In repeatedly mown and mulched green manure leys, the mulched herbage contains substantial amounts of nitrogen (N), which may only slightly contribute to the following crops’ nutrient demand. The objective of the present work was to evaluate the effect of alternative strategies for green manure management on the yield and N recovery of a subsequent spring barley crop, and their short term effects on soil structure and earthworm populations. A field trial was run from 2008 to 2011 at four sites with contrasting soils under cold climate conditions. We compared several options for on-site herbage management and the application of anaerobically digested green manure herbage. Depending on the site, removal of green manure herbage reduced the barley grain yield by 0% to 33% compared to leaving it on-site. Applying digestate, containing 45% of the N in harvested herbage, as fertilizer for barley gave the same yields as whenall herbage was mulched the preceding season. Overall, the apparentNrecovery was enhanced from 7% when all herbage was mulched, to 16% when returned as digestate. A positive effect on earthworm density and biomass was seen after one season of retaining mulch material, rather than removing it. Digestate did not affect the earthworm population, but contributed to higher soil aggregate stability. In conclusion, for spring barley production after green manure ley, the digestate strategy increased N recovery and reduced the risk of N losses. The yield of the succeeding barley crop yield was reduced when N in herbage was not returned as mulch or digestate.
European Journal of Agronomy, 2014, Vol 52, Issue B, p. 90-102