Effect of Tillage On Phosphorus Leaching Through Coastal Plain Soils.

Leaching of phosphorus (P) is a primary water quality concern in soils of the Atlantic Coastal plain where lateral subsurface flow is the dominant P transport pathway. We hypothesize that very high soil P in the upper 2 cm of no-till soils contributes to P leaching via macropore flow and that cultivation will result in overall lower soil P values and less P leaching. We investigated the effect of tillage as a means of reducing P leaching in selected agricultural soils of the Delmarva Peninsula. Intact soil columns of 30-cm diameter and 50-cm length (five replicates) were collected from the Bojac (coarse-loamy, mixed, semiactive, thermic Typic Hapludult), Evesboro (mesic, coated Lamellic Quartzipsamment), and Sassafrass (fine-loamy, siliceous, semiactive, mesic Typic Hapludult) soils. Soil properties range from excessive to somewhat poorly drained and from sand to silty clay loam texure. Soil P stratification with depth was determined by testing the 0-2 cm, 2-10 cm and 10-20 cm layers. To achieve uniform conditions before tillage, soils were pre-irrigated once a week indoors (22-26^o C) with 2 mm of water having simulated rainwater chemistry. Tillage was simulated by gently removing and mixing the upper 20 cm of soil and replacing it in the column. Soils were subsequently leached. Differences due to mixing across high and low P soils and soils of varying texture will be presented.