Submitted to: Mississippi Water Resources Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 15, 2000
Publication Date: N/A
Interpretive Summary: Waste from animals such as chickens and pigs is deposited on the soil of hayfields. Buildup of phosphorus from animal waste occurs. Forages can take up phosphorus from the soil and remove it when forages are harvested for hay. However if forages contain most of their phosphorus in roots or runners then little phosphorus will be removed by hay harvesting. This study looked at where phosphorus was located in a number of different forage plants fertilized with chicken or pig waste. Different forages were evaluated in two locations and the amount of phosphorus was determined in roots, stems, leaves, and flowers of each forage. Over half of the phosphorus was located in either upright stems or stems that spread on the ground called stolons or runners. Farmers should encourage upright stem formation in forages such as annual ryegrass or red clover to take up the most phosphorus with hay harvesting. In plants with stolons or runners such as bermudagrass or white clover, farmers should try to reduce the amount of stolons or runners spreading on the ground since these plant parts can not be harvested as hay. Farmers can increase stem production and phosphorus removal in hay by adjusting cutting treatments, harvesting when the plants are fully mature, and other management techniques.
Technical Abstract: Phosphorus buildup occurs in soils fertilized with poultry litter or swine effluent. Hay harvesting of forages will help remove P from these soils. Little is known about P distribution in plant parts of different forage species. Uptake by leaves, upright stems, and flowers is advantageous since these plant parts can be harvested for hay and P removed from the site. Uptake by prostrate stems and roots ties up P but eventually they decompose releasing P to the environment. This study evaluated a wide range of forage species for P accumulation in roots, stems, leaves, and flowers when grown under poultry litter or swine effluent fertilization at 2 locations in Mississippi. Phosphorus concentration and uptake was determined for plant parts of 4 grasses and 13 legumes under poultry litter fertilization in Collins, MS; 13 legumes under swine effluent fertilization in Crawford, MS; and 3 bermudagrass cultivars under swine effluent fertilization in Crawford, MS. Each study was conducted for 2 years with single harvests taken of annual grasses and legumes at full maturity and 5 harvests taken over 2 years for bermudagrass cultivars. Most P in legumes, annual grasses, and bermudagrass was located in stems or runners. Legume stems had greater P concentrations than grasses, but grass stems contained more P due to their greater dry weight. Leaves contained about 25% of the plant P. Flowers and roots contained relatively little P. The P distribution varied greatly among forages, though stems usually contained the greatest P amount in all species. Due to the greater dry weight of stems, farmers should use management techniques to increase stem production in their forages grown for hay to maximize P removal.