Soil Test Phosphorus Distribution with Long-Term Strip-Tillage and Fertilizer Placement.

Long-term phosphorus placement under strip-tillage tillage can create uniform vertical and horizontal distribution of soil test P (STP).  A corn-soybean study was established in Scandia, Kansas in 2006.  Treatments included a (1) control (No P) and P applied at 39 kg P ha^-1 as (2) broadcast, (3) deep band, (4) broadcast with starter, and (5) deep band with starter.  All fertilizer was applied before planting corn and all plots received strip-tillage.  After 10-years of corn and soybean production, soil samples were collected at 0, 7.6, 15.2, 22.8, 30.4, and 38.0 cm from the row and divided into depths of 0-7.6, 7.6-15.2, 15.2-22.8, and 22.8-30.4 cm, and analyzed for Mehlich-3 STP, pH and soil test K (STK).  Data were analyzed for treatment differences by position and depth using depth as a repeated measure.  Results show significant treatment differences in STP in the in-row sampling (0 cm) at depths 7.6-15.2 and 15.2-22.8 cm.  Greatest P concentrations occurred with deep band, however no differences were found with starter application.  Broadcast and broadcast with starter showed significantly greater STP at BR-9 at 0-7.6cm depth.  There were no differences in pH or STK at any position or depth.  However, general trends show greater potassium concentrations for in-row sampling at depths 0-7.6 cm.  Vertical and horizontal STP stratification was increased significantly with long term fertilizer P placement and minimum tillage. This may require revised guidelines for better soil sampling and management in the field.