Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/21/2002
Publication Date: 7/1/2003
Citation: GASTON, L.A., EILERS, T.L., KOVAR, J.L., COOPER, D., ROBINSON, D.L. GREENHOUSE AND FIELD STUDIES ON HAY HARVEST TO REMEDIATE HIGH PHOSPHORUS SOIL. COMMUNICATION IN SOIL SCIENCE PLANT ANALYSIS. 2003. V. 34. p. 2085-2097. Interpretive Summary: Poultry production is the largest agricultural animal industry in Louisiana, so it is vital to the state's economy. Recent 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. In both greenhouse and field studies, we looked at the potential for hay harvest to remove significant amounts of P from a Louisiana Coastal Plain soil common to the area. In the greenhouse, we grew and harvested five warm-season and five cool-season forages in a soil with elevated P content. In a field study on the same Ruston silt loam soil, we also measured common bermudagrass yield and P uptake as affected by the amount of plant-available P initially in the soil and the amount of poultry litter applied to the soil. Under optimum growth conditions in the greenhouse, alfalfa and crabgrass removed more P than other summer forages, and annual ryegrass removed more P than other winter forages. Uptake by these species was about 80 mg P/kg soil from five harvests during six months of growth. During the five-year course of the field study, bermudagrass removed only about half as much P from the soil, compared with that grown in the greenhouse. The amount of soil P removed from the field depended only on the poultry litter application rate, not the initial P level. Assuming four harvests per season and P uptake rates by annual ryegrass half those obtained in the greenhouse, combined summer bermudagrass and winter annual ryegrass hay harvest may lower soil P by about 50 mg/kg soil each year. Given the current emphasis on development of a state P Index, this information will assist producers in managing and utilizing the nutrients in poultry litter.
Technical Abstract: Runoff from soil with high levels of phosphorus (P) may induce eutrophic conditions in downstream water bodies. Land-application of poultry litter rich in P has resulted in build-up of excessive P in many soils. The studies reported in this paper examined the potential of hay harvest to reduce the level of P in a Louisiana Coastal Plain soil. Five warm-season and five cool-season forages were evaluated in a greenhouse study for P uptake (=biomass yield x tissue concentration) from a Rust on soil (fine-loamy, siliceous, thermic Typic Paleudult) with elevated P concentration. Common bermudagrass (Cynodon dactylon (L.) Pers.) yield and P uptake as affected by fertilization rate with poultry litter and level of soil P were also examined in a field study on Ruston soil. Under optimum growth conditions in the greenhouse, alfalfa (Medicago sativa L.) and crabgrass (Digitaria sanguinalis (L.) Scop.) removed more P than other summer forages, and annual ryegrass (Lolium multiflorum Lam.) removed more P than other winter forages. Uptake by these species was 80 mg P kg**-1 soil in five harvests (average) over six months of growth. During the five-year course of the field study, maximum P uptake by bermudagrass was only about half that obtained in the greenhouse (6 mg P kg**-1 soil per harvest compared with 12.5 mg P kg**-1 soil per harvest). Phosphorus uptake in the field depended on poultry litter application rate, but not level of soil P (Bray 2, Mehlich 3, total inorganic or total P). Assuming four harvests per season and P uptake rates by annual ryegrass half those obtained in the greenhouse, combined summer bermudagrass and winter annual ryegrass hay harvest may lower soil total P by about 50 mg kg**-1 soil per year.