Tuesday, November 14, 2006

Organic Carbon effects on P sorption and release from agricultural soils.

Nathan Nelson, Kansas State University - Plant Pathology, Kansas State University Department of Agronomy, 2707 Throckmorton Plant Sciences Center, Manhattan, KS 66506

Intensified cropping and conservation tillage systems return greater amounts of residue to the soil while reducing organic matter decomposition.  This combination of increased residue and reduced decomposition has increased organic carbon in agricultural soils by as much as 50%.  Increases in organic carbon can affect P sorption and availability in soils because of additional organic matter coatings on adsorptive surfaces and increased potential for cation bridging to interact with P additions to the soils.  The objective of this study is to determine the effects of increased organic carbon resulting from different tillage and cropping systems on P sorption and desorption characteristics of agricultural soils.  Soil samples were collected from long-term tillage and cropping system studies in north eastern and central Kansas.  Treatments involving animal waste application or P fertilizer variables were not included to avoid the confounding effects of different P application rates.  Soil chemical properties determined include P sorption maxima, anion exchange extractable P, oxalate extractable P, Fe, and Al, and P desorption (or hysterisis).  The results of this study will assist in determining if soil management practices, such as conversion from conventional tillage to no-till, will affect availability of applied P fertilizers.

Handout (.pdf format, 554.0 kb)