Nitrogen fertilization value of compost and dried dung in soils with contrasting synthetic nitrogen fertilization histories |
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| Authors: | Adam D Langworthy Ross Corkrey Richard P Rawnsley Pieter J M Raedts James L Hills |
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| Institution: | 1. Tasmanian Institute of Agriculture, University of Tasmania, Burnie, Tasmania, Australia;2. Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Tasmania, Australia |
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| Abstract: | If the production of forage for dairy cattle is to become less reliant on synthetic nitrogen (N) fertilizers, there is need to better understand and account for the N contributed by on-farm and imported organic amendments. A 254-day aerobic soil incubation study (typical length of a growing season in many temperate dairying regions) quantified the inorganic (mineral) N supply from a commercial compost and dried bovine dung (i.e., on-farm effluent solids). Amendments were incubated in soils with contrasting synthetic N fertilization histories (i.e., 70–100 vs. 350–400 kg N/ha per year) to evaluate if higher synthetic N fertilization histories would reduce the lag time that often exists between organic amendment application and significant release of inorganic N for plant uptake. This proposition was based on previous research, which showed greater soil inorganic N availability accelerating organic amendment decomposition. Our experiment did find that the release of inorganic N from evaluated organic amendments was greater in soils with higher synthetic N fertilization histories, but that this effect was not apparent until after the first 6-months of this 9-month experiment. Despite this finding, soils with contrasting synthetic N fertilization histories were not found to differ in their initial inorganic N content, nor microbial activity or other physiochemical properties known to affect N mineralization. Our study highlighted the long-term vision needed when transitioning from synthetic N fertilizers to organic amendments, with most of the N present in the compost and dried dung remaining unavailable for forage production (i.e., remained bound in organic carbon-based molecules). |
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| Keywords: | ammonium manure nitrate nitrogen fertilizer replacement value organic regenerative |
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