Methods

• We collected swine manure from animals fed one of a series of four barley phenotypes (422, 635, 955, and 1070) or a wild variety (Harrington). The barleys contained varying amounts of phytate (10-90% total seed P).
  
  
• Each of the five manures were incorporated into three soils (Table 1) at a N-based (150 mg N kg^-1) or P-based (27.5 mg P kg^-1) application rate on three occasions: days 0, 21, and 36. An inorganic P source (KH₂PO₄) and a control were also included.
  
  
• Soils were incubated for 7 weeks in 250 mL polyethylene containers at 22°C and 20% soil moisture.
  
  
• P solubility was determined by extraction with water (1:100 soil to solution ratio) and sodium bicarbonate (Olsen P) at intervals.
  
  
• Soluble organic P was determined as the difference between extractable total Olsen P and molybdate-reactive P in bicarbonate extracts.
  
  
• Microbial P (fumigation-extraction) was measured at day 49 on the Warden and Declo soils and at all sampling dates for the Portneuf soil.