Location: Agroecosystems Management ResearchTitle: Phosphorus runoff from Coastal Plain forest soil in Louisiana
|FELICIEN, WILLIAM - Louisiana State University|
|WIGHT, JASON - Louisiana State University|
|GASTON, LEWIS - Louisiana State University|
|BLAZIER, MICHAEL - Louisiana State University|
Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2015
Publication Date: 4/5/2016
Citation: Felicien, W.L., Wight, J.P., Gaston, L.A., Blazier, M.A., Kovar, J.L. 2016. Phosphorus runoff from Coastal Plain forest soil in Louisiana. Communications in Soil Science and Plant Analysis. 47(10):1283-1295.
Interpretive Summary: Poultry production is the largest agricultural animal industry in Louisiana, so it is vital to the state’s economy. Research has shown that application of poultry litter for many years has led to a build-up of soil phosphorus (P) in some areas of north Louisiana. This P can negatively impact water quality in nearby lakes and streams. With a field study in a loblolly pine tree forest planted in 1990, we evaluated P losses in both natural runoff and that generated from simulated rainfall during a 6-year period (2001-2006) following six annual applications of four rates (0, 5, 10 and 20 Mg ha-1) of poultry litter to a Louisiana Coastal Plain soil common to the area. Phosphorus losses in runoff from this forest soil were lower than reported for pasture soils at this site, despite the five previous poultry litter additions. We speculate that P may have been retained in an acidic soil layer that was developed under the stand of pine trees, but was not present in the pasture soil. Phosphorus losses in runoff decreased rapidly when poultry litter applications ceased. Within four years, P losses from all treatments were similar. Based on extractable P levels measured in surface soil one meter downslope from poultry litter-amended plots, there was no evidence of offsite movement of P. Since conversion of fertilized pasture to timberland is common in the coastal plain of Louisiana and elsewhere, results of the field study are broadly relevant. Given the current emphasis on non-point source losses of P, this information will assist producers in managing and utilizing the nutrients in poultry litter.
Technical Abstract: Although not a common practice, poultry litter (PL) may be used for forest fertilization. Despite usually low soil phosphorus (P) and runoff under forest, repeated or high rates of PL application may cause appreciable P loss. Phosphorus in natural runoff under loblolly pine (Pinus taeda L.) fertilized with PL, downslope P enrichment of surface soil, and P runoff during simulated rainfall: a) five years post-application, and b) where straw was harvested, were measured. Relationships of runoff P (dissolved reactive, dissolved and total) concentration and load to soil P (Bray-2 and water-extractable P in two depths) and hydraulic conductivity were examined. Post-application loss of P was lower than reported for pasture. There was little downslope P movement. Runoff P was related to the corresponding form of soil P (R2 = 0.28 to 0.48) but likely affected by P leached from the O horizon. Loads could be estimated from regressions.