[Pil-pc-oceania] Soil microbes can cut phosphorus costs (farmonline)

[Deb Guildner]

      Breaking Rural News : GRAINS AND CROPPING

     Soil microbes can cut phosphorus costs
      Australia
      Tuesday, 11 December 2007

      With the cost of phosphorus fertiliser continuing to sit at record 
levels and farmers facing unprecedented fertiliser costs of up to $150 a 
hectare, any means of cutting down costs will be welcomed.
      Researchers have found that a combination of building microbial 
activity and monitoring soil phosphorus levels to ensure expenditure is 
profitable are two good methods of minimising fertiliser bills next season.

      South Australian scientist Ann McNeil, a researcher at the University 
of Adelaide, says soils contain organic phosphorus and by encouraging soil 
microbial activity, growers can encourage phosphorus cycling and increase 
its availability to the plant.

      Traditionally, farmers have accessed in-soil nitrogen reserves, which 
become available through mineralisation following summer rain or through 
growing a legume, but have regarded phosphorus as an unavoidable 
expenditure.

      Dr McNeil says growers can also make use of organic phosphorus in the 
long-term - with no-till systems improving the soil organic matter doing the 
best job of making extra P available.

      Dr McNeill's research shows farming practices which build soil carbon 
also improve organic phosphorus levels and microbial activity.

      However it is not a short-term fix - and that P levels must be 
maintained to promote microbial activity.

      Even though as little as 20pc of applied phosphorus ends up in the 
plant, the "lost" fertiliser still has an important part in stimulating 
microbes and eventually becomes available to plants in other seasons.

      Eighty to ninety per cent of phosphorus in the crop comes from the 
organic phosphorus reserves in the soil, converted by the soil microbes.

      Dr McNeill says it takes a long time to achieve a nutrient balance in 
the soil but by encouraging the soil microbes growers can maintain a healthy 
system with a sustained ability to supply plant-available phosphorus.




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