Poultry litter applications to land have been based on crop N requirements, resulting in application of P in excess of plant requirements, which may cause degradation of water quality in the Chesapeake Bay watershed. The effect of litter source (the Delmarva Peninsula and Moorefield, West Virginia) and composting of poultry litter on N mineralization and availability of P in two soil types (sandy loam and silt loam) was determined in a controlled environment for 120 d. Nitrogen mineralization (percent total organic N converted to inorganic nitrogen) rates were higher for fresh litter (range of 42 to 64%) than composted litter (range of 1 to 9%). The N mineralization rate of fresh litter from the Delmarva Peninsula was consistently lower than the fresh litter from Moorefield, WV. The N mineralization rate of composted litter from either source was not significantly different for each soil type (7 to 9% in sandy loam and 1 to 5% in silt loam) even though composting conditions were completely different at the two composting facilities. Litter source had a large effect on N mineralization rates of fresh but not composted poultry litter. Composting yielded a more predictable and reliable source of mineralizable N than fresh litter. Water-extractable phosphorus (WEP) was similar in soils amended with composted litter from WV and fresh litter from both sources (approximately 10 to 25 and 2 to 14 mg P kg(-1) for sandy loam and silt loam, respectively). Mehlich 1-extractable phosphorus (MEP) was similar in soils amended with WV fresh litter and composted litter from both sources (approximately 100 to 140 and 60 to 90 mg P kg(-1) for sandy loam and silt loam, respectively). These results suggest that the composting process did not consistently reduce WEP and MEP, and P can be as available in composted poultry litter as in fresh poultry litter.

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Composted poultry litter (CPL) may be applied as a mulch in fruit orchards to manage waste and to provide a slow-release nutrient source and weed control. With proper management, poultry manure and bedding (litter) can prevent environmental degradation, such as hypoxia in aquatic communities. Peach (Prunus persica L. `Sunhigh') plots all received preemergence herbicides in May and then the following treatments in June 1998: commercial fertilizer (N at 15 g·m-2), low rate CPL (N at 15 g·m-2 as CPL at 2.9 kg·m-2), high rate CPL (N at 62 g·m-2 as CPL at 11.6 kg·m-2), and no fertilizer or mulch control. Weeds were completely controlled by mulch and herbicide during 1998 but not during 1999. By Sept. 1999, the high rate of CPL had only 27% weed cover compared with 86% for the commercial fertilizer-treated plots. Soil N was highest (NH4-N and NO3-N at 16.4 and 18.6 mg·kg-1 soil, respectively) in plots treated with commercial fertilizer, 6 weeks after treatment (WAT). Soil N did not differ among the two CPL treatments and the control at any time. At the high rate of CPL, there was NH4-N and NO3-N at 3.2 and 0.7 mg·kg-1 soil, respectively, at 6 WAT. Water-extractable P (WEP) in the soil did not differ among the CPL and commercial fertilizer treatments at 6 WAT (P at §14 mg·kg-1 soil). However, at 47 WAT, plots with the high rate of CPL had significantly higher WEP, with P at 30 mg·kg-1 soil vs. 14 mg·kg-1 soil in plots treated with commercial fertilizer. High applications of CPL could elevate P in surface runoff to levels that cause environmental degradation. In general, Mehlich 1-extractable P (MEP) did not differ among the CPL- and fertilizer-treated plots (averaging P at 45 mg·kg-1 soil). MEP was lowest in control plots (averaging P at 21 mg·kg-1 soil). Results indicate that CPL could be used as a weed suppressant without adversely affecting N release to the environment; however, P concentration in soil water may be problematic.

Improper management of poultry manure and bedding (litter) can cause hypoxia in aquatic communities, but poultry waste can be converted to a stable organic fertilizer by composting. Peach trees (Prunus persica L. `Sunhigh') received the following treatments in May 1998: commercial fertilizer (15 g N/m2), low-rate composted poultry litter (15 g N/m2 as 2.9 kg composted litter/m2), high-rate composted poultry litter (62 g N/m2 as 11.6 kg composted litter/m2), and no treatment control. Weeds were completely controlled during 1998, but, by Sept. 1999, the high-rate poultry litter had only 27% weed cover compared with 86% for the commercial fertilizer-treated plots. Soil N was highest in plots treated with commercial fertilizer (16.4 mg N-NH4 and 18.6 mg N-NO3 per kg soil, 6 weeks after treatment) and did not differ among the remaining treatments (in the high rate of poultry litter—3.2 mg N-NH4 and 0.7 mg N-NO3 per kg soil, 6 weeks after treatment). Water soluble P in the soil did not differ among treatments at 6 weeks after treatment (≈12 mg P per kg soil for all treatments) but, at 47 weeks after treatment, plots with the high rate of poultry litter had 30 mg P per kg soil compared with 14 mg P per kg soil in plots treated with commercial fertilizer. In general, Mehlich 1 acid-soluble P did not differ among the litter- and fertilizer-treated plots (averaging 45 mg P per kg soil). Acid-soluble P was lowest in control plots (averaging 21 mg P per kg soil). Results indicate that poultry litter could be used as a weed suppressant without adversely affecting nitrogen release to the environment. However, P mineralization may be problematic and requires further investigation.