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phosphates

Catalogue: GRDC Updates
Lastly the strain is selected for its ability to survive in the soil between seasons... Let's consider if there is a need for inoculation of the crop with free-living N2-fixing organisms... The production of cluster roots and release of organic acids is extremely energy expensive; the plants strategy is to acquire P at any cost (Lynch and Ho 2005)...
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Catalogue: GRDC Updates
It is extremely important to use farm management practices that maintain organic matter levels, especially biologically available organic matter in our soils... Australian soils are inherently low in biologically available carbon carbon inputs have a major influence on soil biological activity... For an introduced biocontrol agent to be effective it must first survive, establish, acclimatize and grow in field soils and interact with the pathogenic organisms alone or in the presence of plant...
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Catalogue: GRDC Updates
Crop Use of Fertiliser, Topsoil and Subsoil P We had 7 experiments in the field under rain-out shelters where we directly measured the uptake of P fertiliser (using radioisotope) under wet (decile 7-8) and dry (decile 2-3) in-season conditions... We applied P fertiliser containing a radioactive tracer that gives the fertiliser a unique 'fingerprint' so that we could track the uptake of fertiliser into the plant... We are examining the value of information that might support decision making around P management including the value of accurate soil P testing and the value of being able to estimate when soil P fertility will fall below sufficiency using modelling techniques...
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Catalogue: GRDC Updates
Understanding and measuring soil water - GRDC Eastern Farming Systems Project.. Small particles (clays) that occupy the same soil volume as large particles (sands) have a greater surface area and are able to hold more water... As the Na+ ion concentration in the soil increases, clay particles move apart and the soil disperses...
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Catalogue: GRDC Updates
Recent work in DAQ00148 and previous projects has focussed on developing new soil testing strategies (0-10cm and periodic 10-30cm testing to determine P and K status), soil tests (BSES P and tetraphenyl borate extractable K to measure slow release P and K reserves) and critical soil test values to trigger fertiliser application responses... Previous results (Spring 2011 Updates) showed that sorghum responses to P bands were improved when band spacing was 50cm or less, and similar trends have been obtained for K band spacings in the winter wheat crop at Brookstead (Table 2), although differences were not statistically significant... Similarly we are now undertaking more work on crop responses to S applications, especially when combined with P and/or K. Quantifying the costs and benefits of getting the right combination of nutrients in the right place at the right time will be essential to maintaining or improving profitability and sustainability of our cropping soils...
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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 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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