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phosphorous management

Catalogue: GRDC Updates
As an example, where appropriate use of fertilisers can increase productivity beyond that currently being attained, adjusting the amount or timing of fertiliser application would result in greater carbon inputs to the soil... Recent research results have also noted that the proportion of residue carbon that is retained in a soil to enhance soil carbon stocks can be enhanced by ensuring that enough nutrients exist in the soil to both satisfy the crop requirements and the requirements to build soil organic carbon... If we use the same bulk density as above (1.2 g/cm3) and restrict our calculations to the top 10 cm of soil where organic carbon is most easily increased, at 2% carbon the soil would contain 24 tonnes C/ha...
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Catalogue: GRDC Updates
Getting nutrition right in 2011 after a big year in 2010.. It is important that water soluble phosphorus is placed in the seed furrow or as close as possible to the seed furrow to allow access for developing root systems... The fertiliser concentrations in the seed zone are greatly influenced by the amount of soil disturbance, air velocity, ground speed, seeding depth, stubble cover, soil texture and moisture content during the seeding operation and its interaction with the concentration of fertiliser delivered to each seed-row...
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Catalogue: GRDC Updates
Plot of cumulative crop P uptake against Colwell-P for 15 soils used in the glasshouse depletion experiment... Plot of relative yield against Colwell-P for 15 soils used in the glasshouse depletion experiment... The results in Fig. 2 indicate that the BSES-P (440 mg P/kg) in Soil 9 is not as available as the BSES-P in Soil 8 or Soil 3 (382 mg P/kg and 91 mg P/kg respectively)...
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Catalogue: GRDC Media
WA growers can save by cutting phosphorus rates.. Western Australian grain growers can make significant cost savings by reducing phosphorus application to 'maintenance rates', and using soil test results to fine-tune them... "Researchers need to determine the 'maintenance rates' required for different soils and regions of WA so reliable maintenance recommendations can be made for growers," Dr Wong said...
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Catalogue: GRDC Updates
And it is vitally important to understand as much as possible, and at present we do not know nearly enough to allow us to sustainably use soil to provide enough food for the future... Before talk of any new technology, any new grain-product, or new tillage platform, a key issue for Australia's agricultural business must be the development of a soil protection policy that will allow the sustainable growth of production from our soil reserves... We now know that surfactants produced from roots allow the whole plant to access water and phosphorus at no extra energetic cost (Read et al., 2003); fungi play a huge role in stabilising soil and altering gas diffusion in soil system (Crawford et al., 2012), as well as producing hydrophobic substances that help stabilise soil by lowering water entry into slaking soils (Young et al., 2012)...
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Catalogue: GRDC Updates
Without P fertiliser addition, continuous cropping caused a decline of 55%, 35% and 10% in total P from the 0-10, 10-30 and 30-60 cm layers respectively, compared to an uncropped reference soil... Previous work has shown that an index calculated as (Colwell-P/PBI) is highly correlated with immediately available P across a wide range of Queensland soils... The results suggest that Colwell-P is probably a good indicator of P availability in the surface soil during crop establishment (and useful to diagnose the need for starter P) whereas BSES-P is probably a better indicator of subsoil P reserves that are accessed by the crop later in the growing season...
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Catalogue: GRDC Updates
In the northern grains region P is commonly the next limiting nutrient after N; an adequate supply is vital to ensure N is used efficiently... Given that sorghum is generally a dominant crop in many rotations in the east of the Northern Grains Region and a significant secondary crop in most other areas, it is of significance to recognise that the recent research evidence for increasing the replacement/ maintenance rates for sorghum based on the research from Lester et al. indicating that the commonly used removal figure of 2.3 kg P/tonne (0.23 % P in grain) quoted in the NLWRA 2001 is probably too low for local condition... More recent studies have indicated that 3.7 kg P/tonne (0.37 % P in grain) is more realistic for modern varieties grown on the soils of the vertosols of the Darling Downs and Nthn NSW. Combining higher unit removal and high yield per unit of soil moisture makes sorghum the most influential determinant of soil P status in many areas and a key factor in soil P decline even where replacement rates are targeted...
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Catalogue: GRDC Updates
Partial P budgets (P applied minus P removed in harvested product) are generally negative across the northern grains region indicating that soil P reserves are being used to support crop growth, but the uncertainty in prediction of crop P requirements from pre-plant soil tests has been highlighted by the results obtained from numerous P rate field experiments undertaken in GRDC project DAQ00084... To assess the availability of this acid extractable P, iron oxide strips were used as 'sinks' to continuously remove P from the soil solution forcing P desorption and dissolution of P compounds to replenish soil solution P. Figure 2 indicates that the acid extractable fraction was a major contributor of P to the soil solution and is potentially available to crops... Field experiments have confirmed the unreliability of Colwell-P for discriminating P-responsive from P-adequate sites, even if the Colwell-P status of the sub-surface is considered as being more representative than the 0-10 cm layer of the soil being exploited by the crop roots...
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Catalogue: GRDC Updates
New ways to estimate crop needs and deliver P to improve the return on fertiliser investment.. The implications of this from a productivity perspective are unclear, but early results are suggesting that some significant yield gains may be possible on these soils... While the results suggest that once soils have become depleted in subsoil P significant yield gains can be achieved by improving soil P status, there are a large number of practical issues that need to be resolved...
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Catalogue: GRDC Updates
Toward a Better P Nutrition Package: Diagnosing P Status and Application Strategies to Improve Fertiliser Response.. Preliminary results suggest that once subsoil P becomes limiting, yield losses can become substantial and major changes to P application strategies will be needed... Surplus or deficit was calculated from P inputs in fertilizer minus P removed in grain...
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