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phosphorous management

Catalogue: GRDC Updates
Graph two is for a heavy clay Black Vertosol from Spring Ridge; results show the plant available water capacity (PAWC) is 272mm... Rooting depth should be determined through perusal of physical and chemical data and the physical observation of roots and water extraction through soil coring and/or electronic monitoring... Simulation of water storage using the >100 year climate record shows that a short fallow from wheat (assuming a dry soil profile at harvest in November of the previous year) results in a 50% chance of at least 110mm (range of 0-300mm) of water being available for an April planting at Spring Ridge and 80mm (range of 0-180mm) at Nyngan (Figure 8)...
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Catalogue: GRDC Updates
Sandy, acid soils in high rainfall areas are most prone to potassium deficiency, particularly if cut for hay... Regional nutrient budgets show a progressive drawdown of potassium (K) as it is removed in plant products and, depending on cropping system and soils, there may be a need to consider the role of K. Use of K in Australia declined from 183 kt K in 2003 to 149 kt K in 2011 but did recover somewhat in 2012... Around ten times more K will be removed in hay than grain...
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Catalogue: GRDC Updates
Figure 1: Effects of (a) application of an additional 40-60 kg P/ha to soils prior to planting, relative to normal starter P applications alone; and (b) placing that additional P deeper in the soil profile (15-20cm), compared to surface (5-7cm) bands... half of the soil P removed by cropping comes from below the top 10cm and about 90% of that removed P comes from forms/pools of P not measured in the Colwell (bicarbonate P) soil test; and (ii) when luxury rates of P are applied annually , >95% of the residual P stays in the top 10cm of the profile and the depletion of the subsoils continued unchanged... , we used a bioassay to assess how much of the P in the various pools was actually available for plant uptake, and how well this correlated with what the Colwell test predicted...
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Catalogue: GRDC Updates
Managing nutrition on soils that have been treated for water repellence by cultivation.. A comparison of N uptake at 10 N and 50 N weeks after sowing showed significant increases in N uptake in the nil and banded wetter though not in mouldboard and spading... The results suggest that soil nitrogen is more available in the mouldboard and spading treatments than in the nil and banded wetter...
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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 Media
Recent Grains Research and Development Corporation-funded (GRDC) research in the northern region shows native remnant vegetation measures around three per cent soil organic carbon (OC) in the top 10 centimetres of the soil... Soil that has been cropped long term is about 1% OC, which indicates long term cropping has decreased OC by 2%.This is a massive drop in the real value of land... A 2% decrease equates to at least 20 tonnes per hectare of OC lost from the soil (assuming bulk density of only 1.0)...
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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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