Effect of Solid Cattle Manure Application Rate and Placement Method On Supply Rates of Phosphate and Nitrate At the Surface of a Black Chernozem In East-Central Saskatchewan.

Placement of solid cattle manure (SCM) may influence the supply of inorganic nutrient ions at the soil surface that are available for biological uptake and interaction with run-off water. The objective of this study was to determine the effect of different SCM placement methods on soil PO₄ –P and NO₃-N supply rates at the soil surface over two growing seasons. Anion exchange membrane probes (PRSä) were inserted at a depth of 1 cm for a 2 hr period every 2 weeks over an 8 week period in plots that had SCM applied in the spring at 60 t ha^-1 using broadcast alone, broadcast and incorporated and subsurface injection placement methods. During the first 30 days after seeding, the application of SCM significantly (p≤0.10) increased the supply of P compared to control treated plots. In subsurface injection treatment in 2008, the soil PO₄-P supply increased from 1.17 µg P cm^-2 2hr^-1 immediately following seeding operations to 2.12 µg P cm^-2 2hr^-1 six weeks after seeding.  Overall, there was no significant effect of placement method on surface soil phosphate supply. Eight weeks after seeding in 2009, soil NO₃-N supply rates ranged from 0.45 µg NO₃-N cm^-2 2hr^-1 in the broadcast alone treatment to 0.92 µg  NO₃-N cm^-2 2hr^-1 in the subsurface banded treatment. Placement of SCM in subsurface bands resulted in higher supply rates of NO₃-N compared to other placement methods possibly due to enhanced mineralization when manure is placed below the surface.