Evaluation of Composted Poultry Litter Use in Horticulture
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The U.S. poultry and egg industry is valued at billions of dollars in gross farm receipts and employs hundreds of thousands of people. A Survey by the United States Department of Agriculture in 2008 revealed that in Alabama alone, the poultry industry generates over $2 billion in gross farm receipts and employs over 78,000 people. Over the past several decades the poultry industry has expanded exponentially. With this growth comes the problem of poultry waste disposal. It is estimated that 16.6 million tons of poultry litter is produced in the United States each year and 2 million tons of litter is generated by the poultry and egg industry each year in Alabama alone. Poultry farmers face the challenge of storing this material, which occupies valuable space on their farms. Often disposal can be costly, and there are also many environmental problems which arise when large amounts of poultry litter are mishandled. Poultry producers must find a way to dispose of this manure in a way that is both economically sound and environmentally safe. The objective of this research was to evaluate the use of composted poultry litter and determine what areas of the horticulture industry that CPL can be the most beneficial. Results from these studies may help determine how composted poultry litter can be used beneficially in the landscape and container nursery industries while providing poultry producers an environmentally sound means of waste disposal. Two experiments were conducted evaluating a variety of commonly grown nursery crops for growth in alternative wood based substrates. Whole Tree (WT) and Clean Chip Residual (CCR) are potential new nursery substrates that are by-products of the forestry industry containing high wood content. Initial immobilization of nitrogen is one limitation of these new substrates; however the addition of composted poultry litter (CPL) to substrates containing high wood content could balance initial nitrogen immobilization and provide an inexpensive fertilizer source for growers. This study evaluated the growth of five woody nursery crops being grown in WT, CCR, and pinebark (PB) with the addition of CPL or peat as a substrate amendment. Results indicate that woody nursery crops can be grown successfully in WT and CCR substrates 6:1 (v:v) with CPL. Use of CPL in WT and CCR substrates provides an alternative to traditional PB plus peat based combinations in container plant production while providing poultry producers an environmentally sound means of waste disposal. Three additional experiments involved the application of CPL to landscape annual beds and the evaluation of plant performance as well as non-point water pollution potential. The objective of these studies was to evaluate composted poultry litter as a fertilizer source for bedding plants at various rates in comparison with commercially available inorganic fertilizers for three commonly used landscape annual bedding species, ‘Quartz Scarlet’ verbena, ‘Celebrity Red’ petunia, and Dusty Miller. Raised beds were constructed and before planting 10 treatments were applied: Peafowl garden grade fertilizer 13N-5.6P-10.9K (13-13-13) at rates of 4.9 g N/m (1 lb N/1000 ft) and 9.8 g N/m (2 lb N/1000 ft), Polyon 13N-5.6P-10.9K (13-13-13) at rates of 4.9 g N/m (1 lb N/1000 ft) and 9.8 g N/m (2 lb N/1000 ft) and composted poultry litter at rates of 4.9 g N/m (1 lb N/1000 ft), 9.8 g N/m (2 lb N/1000 ft), 19.6 g N/m (4 lb N/1000 ft), 29.4 g N/m (6 lb N/1000 ft), 39.2 g N/m (8 lb N/1000 ft), and 49 g N/m (10 lb N/1000 ft). A control group receiving no fertilizer application was also maintained. Soil water leachates were collected using suction cup lysimeters 0.6 m (2ft) long and 5.1 cm (2 in) in diameter with a ceramic cap 7.6 cm (3 in) long and 5.1 cm (2 in) wide. Results from these experiments provides evidence that composted poultry litter could be used as a substitute for conventional inorganic fertilizers when used at the same nitrogen rate and may also be applied at much higher rates than inorganic fertilizers resulting in plants with greater size while minimizing negative environmental impacts.