You are here

critical value

Categorised under:

Catalogue: GRDC Updates (West)
Phosphorus management is characterized by an initial build-up phase that corrects P deficiency followed by a maintenance phase after soils reach the Colwell P values needed for near maximum production (critical values)... For example, if we removed 5 kg P/ha in the form of P contained in grains and we applied 10 kg P/ha as fertiliser, then the P balance efficiency is 5/10x100 = 50 %. P balance efficiency allows us to assess along with soil test P data if we are building-up, maintaining or depleting soil P... We estimate that about 87% of the wheat paddock soil samples examined are no longer P deficient (exceed their critical values)...
Related categories:
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...
Related categories:
Catalogue: GRDC Media
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... "Growers should also be aware that in some soils, severe water repellence, severe acidity and the presence of root diseases may increase the apparent critical soil phosphorus level required by crops," Dr Wong said...
Related categories:
Catalogue: GRDC Updates
We first determined (1) the amount of P applied as fertilisers to crops in WA and (2) the amount of P removed in harvested grains by multiplying grain yield by the P content of the grains... For example, if we removed 5 kg P/ha in the form of P contained in grains and we applied 10 kg P/ha as fertiliser, then the P balance efficiency is 5/10x100 = 50 %. P balance efficiency allows us to assess along with soil test P data if we are building-up, maintaining or depleting soil P... We estimate that about 87% of the wheat paddock soil samples examined are no longer P deficient (exceed their critical values)...
Related categories:
Catalogue: GRDC Updates
The interpretation of the values generated from those soil tests has remained a dark art and this short paper hopes to summarise 'where we are at' with the principles we use to interpret all those soil tests that have been increasingly adopted by industrious agronomists and producers... Considerably more work is required to improve the precision of these critical values, and to understand the mechanism behind the increase in those values where soil Na or Mg status is high... We have been working on a method to estimate the reserves of K available in each soil and the results of this research have been presented in previous Updates...
Related categories:
Catalogue: GRDC Factsheets
Other measurements that aid the interpretation of soil nutrient tests include soil pH, percentage of gravel in the soil, soil carbon/organic matter content, P sorption capacity [currently measured as Phosphorus Buffering index (PBi)], electrical conductivity, chloride and exchangeable cations (CeC) including aluminium... for canola the critical value measured in the 0 to 10cm soil layer is 44mg K/kg for all soils to achieve 90 per cent of maximum yield... The critical wheat soil S test value measured in the 0 to 30 cm soil layer is 4.6mg S/kg for all soils to achieve 90 per_cent of maximum yield...
Related categories:
Catalogue: GRDC Factsheets
Other measurements that aid the interpretation of soil nutrient tests include soil pH, percentage of gravel in the soil, soil carbon/organic matter content, P sorption capacity [currently measured as Phosphorus Buffering index (PBi)], electrical conductivity, chloride and exchangeable cations (CeC) including aluminium... for canola the critical value measured in the 0 to 10cm soil layer is 44mg K/kg for all soils to achieve 90 per cent of maximum yield... The critical wheat soil S test value measured in the 0 to 30 cm soil layer is 4.6mg S/kg for all soils to achieve 90 per_cent of maximum yield...
Related categories:
Catalogue: GRDC Factsheets
Other measurements that aid the interpretation of soil nutrient tests include soil pH, percentage of gravel in the soil, soil carbon/organic matter content, P sorption capacity [currently measured as Phosphorus Buffering index (PBi)], electrical conductivity, chloride and exchangeable cations (CeC) including aluminium... for canola the critical value measured in the 0 to 10cm soil layer is 44mg K/kg for all soils to achieve 90 per cent of maximum yield... The critical wheat soil S test value measured in the 0 to 30 cm soil layer is 4.6mg S/kg for all soils to achieve 90 per_cent of maximum yield...
Related categories:
Catalogue: GRDC Factsheets
Other measurements that aid the interpretation of soil nutrient tests include soil pH, percentage of gravel in the soil, soil carbon/organic matter content, P sorption capacity [currently measured as Phosphorus Buffering index (PBi)], electrical conductivity, chloride and exchangeable cations (CeC) including aluminium... for canola the critical value measured in the 0 to 10cm soil layer is 44mg K/kg for all soils to achieve 90 per cent of maximum yield... The critical wheat soil S test value measured in the 0 to 30 cm soil layer is 4.6mg S/kg for all soils to achieve 90 per_cent of maximum yield...
Related categories:
Catalogue: GRDC Factsheets
Other measurements that aid the interpretation of soil nutrient tests include soil pH, percentage of gravel in the soil, soil carbon/organic matter content, P sorption capacity [currently measured as Phosphorus Buffering index (PBi)], electrical conductivity, chloride and exchangeable cations (CeC) including aluminium... for canola the critical value measured in the 0 to 10cm soil layer is 44mg K/kg for all soils to achieve 90 per cent of maximum yield... The critical wheat soil S test value measured in the 0 to 30 cm soil layer is 4.6mg S/kg for all soils to achieve 90 per_cent of maximum yield...
Related categories:

Pages