Submitted to: Experiment Station Bulletins
Publication Type: Experiment Station
Publication Acceptance Date: 4/16/2000
Publication Date: 4/16/2000
Citation: Faulkner, S.M., Wood, C.W., Reeves, D.W., Raper, R.L. 2000. Phosphorus redistribution via tillage in nutrient overloaded soils. Southern Association of Agricultural Scientists, Agronomy Section, Memphis, TN. Interpretive Summary: Poultry production is a major industry in many areas of the nation, including Alabama, Georgia, Arkansas, Delaware, and Maryland. Alabama alone produces more than 2 million tons of broiler litter annually. Broiler litter is most often disposed of by application to local agricultural land. Although litter is a beneficial source of plant nutrients, long-term application can lead to degradation of surface water quality via phosphorus run-off. This Ala. Agric. Exper. Stn. - ARS cooperative study determined the impact of tillage on P in soils overloaded with broiler litter. Tillage treatments of no-till, chisel plowing followed by disking, moldboard plowing followed by disking, and each of these in combination with paraplowing, a form of deep non- inversion tillage, were applied to a pasture having a history of broiler litter application and an extremely high soil test phosphorus level. Soils were analyzed for total and inorganic extractable phosphorus. Moldboard plowing greatly reduced surface soil phosphorus concentrations compared to chisel plowing and no-till. Paraplowing further reduced phosphorus concentrations in some instances, although the decrease is not necessarily of environmental significance. Results of this study indicate that tillage is quite effective in reducing phosphorus in surface soil by incorporating litter into the soil profile, and mixing high phosphorus-concentration soils with lower phosphorus-concentration subsoils. Moldboard plowing soils with extremely high soil test phosphorus concentrations every 5 to 10 years may offer a means for diluting phosphorus and reducing risks of environmental impacts.
Technical Abstract: Land application of poultry litter is an economical means of waste disposal. Unfortunately, long-term poultry litter application to agricultural land often results in build-up of surface soil phosphorus (P) to excessive levels. Because P is the limiting nutrient in freshwater eutrophication, runoff from this land is a leading cause of surface water degradation. Application of poultry litter prior to tillage may reduce surface soil accumulations of P by incorporation. We determined the effectiveness of tillage systems in diluting surface soil P. Tillage treatments included no-till, chisel/disk, moldboard/disk, and each of these in combination with paraplowing. Treatments were applied to soils overloaded with poultry litter in Alabama's Appalachian Plateau region. Soils were sampled at 0-5, 5-10, 10-15, 15-30, 30-60, and 60-90 cm increments and analyzed for Mehlich-I extractable and water extractable P. Significant differences between treatments were found only in the 0-5 and 5-10 cm depths. Deep inversion of soil profile by moldboard plowing was found to best redistribute P.