In recent decades several pasture legumes have been available in southern Australia as potential alternatives to the most widely used annual pasture legume Trifolium subterraneum. Little is known about their soil phosphorus (P) requirements, but controlled environment experiments indicate that at least some may differ in their P fertiliser requirements. In this study, pasture legume varieties, including T. subterraneum as the reference species, were grown at up to four sites in any one year over a 3-year period (in total, seven site × year experiments) to measure herbage growth responses in spring to increased soil P availability. A critical soil test P concentration (corresponding to 95% maximum yield) was estimated for 15 legumes and two pasture grasses. The critical soil P requirements of most of the legumes did not differ consistently from that of T. subterraneum, indicating their soil fertility management should follow the current soil test P guidelines for temperate Australian pastures. However, the critical P requirement of Medicago sativa was higher than that of T. subterraneum, but remains ill-defined because extractable soil P concentrations in these experiments were often not high enough to permit a critical P estimate. Three forage crop legumes (Trifolium incarnatum, Trifolium purpureum, Trifolium vesiculosum) and two pasture legumes (Ornithopus compressus, Ornithopus sativus) had lower critical soil test P concentrations. It may be feasible to manage pastures based on these species to a lower soil test P benchmark without compromising yield.
Plant available soil phosphate is frequently deficient for crop and pasture production on organic farms in southern Australia. Improved P management, including developing a fertiliser product conforming to organic farming regulations, is required to sustain and increase production on these farms. Reactive phosphate rock (RPR) and elemental sulphur (S) are natural products. Field and pot experiments were established to measure the impact of ground RPR, and co-treatment of RPR with finely ground S, on available soil phosphate (Olsen P), plant dry matter, and the P concentration (%) and content (kg P ha -1
26Both polycyclic aromatic hydrocarbons (PAHs) and naphthenic acids (NAs) 27 are natural components of fossil fuels but are also widespread, toxic and 28 environmentally persistent pollutants.
Spatial and temporal variation in soil Mn2+ was observed over a 12-month period at two field sites near Gerogery and Binalong in southern New South Wales (NSW), Australia. Three pot experiments were then conducted to emulate the range of soil Mn2+ concentrations observed in the field and to determine the effect of different concentrations on lucerne and subterranean clover seedling growth, as well as to determine the effect of heating a soil on pH and Mn2+ concentrations. Concentrations of soil Mn2+ in the surface 0.20 m varied at a given sampling date by up to 288% (2.5–9.7 µg/mL) and 183% (8.7–24.6 µg/mL) across the Gerogery and Binalong field sites, respectively. At both sites, the concentration of soil Mn2+ in a given plot also varied by up to 175% between sampling times. There was little consistency between sites for seasonal fluctuations of soil Mn2+, although in both instances, peaks occurred during months in which newly sown lucerne plants might be emerging in southern NSW. Pot experiments revealed that high concentrations of soil Mn2+ reduced lucerne seedling survival by 35%, and on seedlings that did survive, reduced shoot growth by 19% and taproot length by 39%. Elevated concentrations of soil Mn2+ also reduced subterranean clover seedling survival by up to 55% and taproot length by 25%, although there were few effects on subterranean clover in treatments other than those imposing the highest soil Mn2+ concentrations. The third pot experiment demonstrated that elevated soil temperatures led to increased soil pH and increased soil Mn2+ concentrations, attributable to a decrease in biological oxidation of soil Mn2+. This was in contrast to the commonly anticipated response of a decline in soil Mn2+concentrations as soil pH increased.
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