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Title: WATER QUALITY IMPACTS OF CONVERTING TO A POULTRY LITTER FERTILIZATION STRATEGY

Author
item Harmel, Daren
item Torbert, Henry - Allen
item Haggard, Brian
item Haney, Richard
item DOZIER, M - TEXAS A&M

Submitted to: Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2004
Publication Date: 11/12/2004
Citation: Harmel, R.D., Torbert, H.A., Haggard, B.E., Haney, R., Dozier, M. 2004. Water quality impacts of converting to a poultry litter fertilization strategy. Journal of Environmental Quality. 33(6):2229-2242.

Interpretive Summary: The water quality impacts of poultry litter application to cultivated and pasture watersheds in the Blackland Prairie of Texas were evaluated in this three year study. Nutrient losses at the edge of new litter application fields were compared to losses under a traditional fertilization strategy. The impact on downstream water quality was also examined. Results for the fallow year with no fertilizer application illustrated that nutrient loss was relatively low and similar between same-landuse watersheds. However, following litter application, phosphorus concentrations increased as application rate increased. The amount of phosphorus in runoff also increased in each of the three years, which coincided with increases in soil phosphorus levels. Results also demonstrated that commercial fertilizers can be much more susceptible than litter to loss in rains soon after application. When the cultivated and pasture watersheds were compared in the years with litter application, the amount of nitrogen in runoff was higher in the cultivated fields than the fields. Also, nitrogen and phosphorus losses from the pasture watersheds were lower than from the cultivated watersheds in each study year due to lower runoff volumes from the pasture areas. The downstream watersheds experienced much lower nutrient loads, on a per area basis, and much lower concentrations than the application fields. These results demonstrate that a low rate annual litter application with supplemental nitrogen can supply needed nutrients without detrimental water quality impacts.

Technical Abstract: The water quality impacts of poultry litter application to cultivated and pasture watersheds in the Blackland Prairie of Texas were evaluated in this three year study. Edge-of-field nutrient losses in surface runoff from new poultry litter application fields were compared to losses under a traditional inorganic fertilization strategy. The impact on downstream water quality was also examined. Nutrient losses were relatively low and similar between same-landuse watersheds in the fallow year with no fertilizer application. However, in each year following litter application, ortho-phosphate concentrations increased as application rate increased within each landuse group. The increased concentrations of ortho-phosphate in runoff coincided with increased extractable soil phosphorus. Inorganic nutrients were much more susceptible to loss in runoff events soon after application than were organic nutrients. Under litter application, nitrate and ammonium concentrations in runoff were higher from cultivated watersheds than from pasture watersheds, but landuse did not affect ortho-phosphate concentrations. Also, nitrogen and phosphorus loads from the pasture watersheds were significantly lower than from the cultivated watersheds in each study year due to lower runoff volumes from the pasture watersheds. Downstream nutrient concentrations and per-area loads were much lower than from edge-of-field stations. These results demonstrate that a low annual litter application rate (4.5 mton ha-1 or less) with supplemental nitrogen can supply needed macro- and micro-nutrients without detrimental water quality impacts.