Recently, rising energy costs have led to a dramatic increase in the price of synthetic fertilizer (Huang, 2009). Between 2002 and 2007 the cost of synthetic fertilizer N per acre rose by over 200% for pecan (Wells, 2009a). This sharp increase in the cost of a single input dramatically reduces the profit margin for pecan producers. Legumes and manure, produced by cattle grazing the orchards, were commonly used to provide fertilizer N for pecan trees in the early years of the southeastern pecan industry. Synthetic fertilizers were readily available at affordable prices after World War II, which led to their wide-scale use, replacing legumes and manure as nutrient sources for pecans (White et al., 1981). As air-blast sprayers were developed and put into use for pesticide application, grazing cattle in the orchard was discontinued in many areas.
Rising N fertilizer costs have led pecan producers to once again consider the use of various legumes such as crimson clover as an orchard floor cover to supplement tree N requirements. Smith et al. (1996) suggested that a combination of crimson clover and hairy vetch (Vicia villosa Roth) could be used as a cover crop to meet the N requirement of pecan in Oklahoma; however, little research in this regard has been conducted in the southeastern United States. Wells (2011a) suggested that crimson clover could provide up to 75 kg·ha−1 N 2 years after establishment, although it was not available until late in the growing season. In 2005, clover (Trifolium sp.) was used in only 15% of surveyed pecan orchards in Georgia. By 2008, nearly half of all pecan orchards surveyed used clover as an orchard floor cover (Wells, 2009b).
Georgia poultry farmers produce over 10.2 million tons of poultry litter annually in the production of meat and eggs, generating ≈20% of the poultry litter produced in the United States (Dunkley et al., 2011). Proper application of litter to the land as a soil amendment is an appropriate use for the waste product. The organic material and nutrients found in poultry litter are beneficial byproducts that have proven useful in amending agricultural soils (Mitchell and Tu, 2005).
The response of N availability and chemical and biological soil quality indicators to poultry litter and clover use in pecan orchards has been previously reported (Wells, 2011a, 2011b); however, significant questions persist regarding the overall effects of poultry litter and clover on pecan tree nutrition and production. The objective of this study was to investigate the effects of these nutrient sources on orchard soil, horticultural, and nut quality parameters of pecan in the southeastern United States.
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