Results

• Manure from swine fed low phytate grains contained 25-54% less total P and 10-46% less water soluble P compared to those fed the wild variety grain, and had variable amounts of phytic acid in the manures (Fig 1 and Table 2).
  
  
• Manures having the greatest total and water soluble P also had the greatest P solubility after soil incorporation, even when applied at the same total P rate (Figs 2 and 3).
  
  
• The phytic acid content of the manures was significantly correlated with Olsen P, but this only explained 48% of the variability (Table 3).
  
  
• Microbial P was closely correlated with the water soluble and Olsen P concentrations of the treated soils (Fig 4).
  
  
• Total P in the manures was the best predictor of P solubility after incorporation into the soil, though correlations were stronger for Olsen P than WSP (Table 3).
  
  
• As the amount of carbon added to the soils increased, Olsen P decreased (when applied at the same total P rate) in all manured soils (Fig 5).