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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). [ABSTRACT FROM AUTHOR]

In many south-eastern Australian dairying regions, supraoptimal ambient temperatures (Ta > 30°C) often challenge the perennial ryegrass (Lolium perenne L.)-dominated feed-base during the summer months. A glasshouse experiment was undertaken to identify alternative summer-active temperate (C3) perennial forages more tolerant of supraoptimal temperature stress (day/night Ta of 38/25°C) than perennial ryegrass. Supraoptimal temperature stress was mposed both with and without irrigation. Chicory (Cichorium intybus L.) was the only species to survive 18 days of combined supraoptimal temperature stress and non-irrigation. Lucerne (Medicago sativa L.), plantain (Plantago lanceolata L.), and tall fescue (Festuca arundinacea Schreb.) survived 12 days of this treatment. Twelve days of exposure to these conditions caused death of perennial ryegrass, prairie grass (Bromus catharticus Vahl.), cocksfoot (Dactylis glomerata L.), birdsfoot trefoil (Lotus corniculatus L.), and red clover (Trifolium pratense L.). Irrigation (daily to through drainage) mitigated detrimental effects of imposed supraoptimal temperature stress on the growth and survival of all species. Chicory and to a lesser extent lucerne, plantain, and tall fescue may have a role to play in south-eastern Australian dairying regions, where supraoptimal temperature stress is a frequent and ongoing issue. [ABSTRACT FROM AUTHOR]