Author
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GASCHO, GARY - UNIV. OF GEORGIA |
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Hubbard, Robert |
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Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/3/2005 Publication Date: 2/1/2006 Citation: Gascho, G.K., Hubbard, R.K. 2006. Long-term impact of broiler litter on chemical properties of a coastal plain soil. Journal of Soil and Water Conservation. 61(2):65-74. Interpretive Summary: The large broiler industry in Georgia is expanding rapidly and figures released in 2003 showed that the value exceeded $2.1 billion from 1.26 billion birds. Nearly all the current expansion is in the Coastal Plain of South Georgia. Presently there are approximately 220 houses in the Coastal Plain with each broiler house resulting in approximately 150 tons litter/year. One major reason for the current expansion in South Georgia is the abundance of agricultural crops for disposal (use) of the waste (broiler litter, BL) and the lack of the same in the northern portions of the State. Georgia cotton acreage has more than quadrupled in the past 8 years and is currently around 1.5 million acres, surpassing peanut acreage. Given the increase in poultry production in the Coastal Plain it is apparent that applications of broiler litter will be made on land planted in cotton & peanuts. A double-cropped, irrigated, conservation-tilled 3-yr rotation was started in Tifton, GA in 1996 and continued through 2001 to determine the effects of broiler litter application on crop nutritional needs and soil chemistry. Cotton, peanut and pearl millet for grain were planted in summer and wheat and canola were planted in winter. Litter application provided yield and value/acre increases for cotton, grain pearl millet, wheat and canola. High rates of broiler litter resulted in rapidly increasing soil test P, signaling potential problems in the future. Overall results from the study should be useful in making recommendations for litter rates and economically efficient applications of fluid fertilizers following litter application. Technical Abstract: Broiler chicken (Gallus gallus) production is increasing rapidly in the Southern Coastal Plain where there is an abundance of agricultural crops. The litter (manure + bedding material) is a proven source of nutrients for many of the crops. We measured the pH, C, and extractable nutrient elements to a depth of 90 cm prior to and following 7 years of an irrigated conservation-tilled double-cropped rotation. Litter was surface-applied at 4 rates (0, 4.5, 9.0, and 13.5 Mg/ha/y) during the first 5 years of the rotation. No environmental problems due to litter application were demonstrated during this 7-year study. Several trends in the data suggest that there will likely be problems with longer-term applications at high rates in the intensive crop rotation. Increases of extractable P, Zn, and Cu (contained in broiler feed) are of greatest concern. Phosphorus, extracted by the Mehlich-1, increased > 100 mg/kg in the surface soil at the greatest BL rate. Many crops will thrive when soil P is high, but depending on slope and other soil properties potential exists for losses of P with soil particles or in the water phase of runoff. Such losses have been correlated with extractable P. Potassium from litter appeared to move to depths beyond the rooting zone of some crops. Concentrations of Cu increased 4 fold and Zn 5 fold in the top soil at the greatest rate of litter application. Continuance of the applications at high rates will eventually lead to toxicity, particularly Zn toxicity in peanut (Arachis hypogaea L.). Potential benefits from broiler litter were attained by the maintenance of pH and an increase of 2.7 Mg C/ha in the top 15 cm. Results of the study suggest that litter can be utilized without negative environmental effects when it is applied at conservative rates. |
