Season Dynamics of Phosphorus Fractions Under Center Pivot Irrigation.

The forms of soil phosphorus (P) play a large role in the availability of P to both plants and the environment.  As with any nutrient, P has a cycle that it moves through where the availability of P to the soil solution will increase or decrease.  Changes in P fractionations have been studied in either short time frames (minutes to hours) or over multiple years.  This study investigated the seasonal dynamics of soil P during the growing season of maize under center pivot irrigation in neutral and soils with biosolids additions.  Soil samples were collected every other month during the growing season from four fields, where each field contained two soil series, representing a total of four soil series.  The forms of P were fractionated into different pools of both inorganic and organic P.  Soil samples also were analyzed to determine the concentration of Olsen extractable P to determine how changes in Olsen P would be related to changes in forms of soils P.  Results will be discussed.