Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2003
Publication Date: N/A
Citation: Interpretive Summary: Fruit tree orchard floor management should enhance fruit tree productivity and also protect natural resources. Mulching can be used as an alternative to herbicides to manage weeds, and the use of organic material such as composted poultry litter (CPL), could also help with proper disposal of waste. Nitrogen (N) and phosphorus (P) release rates from field applications of composted manures can be highly important because both N and P can contribute to degradation of freshwater and marine ecosystems. The objectives of this study were to determine the effect of CPL application as a mulch below peach trees on weed control, peach yield, and soil N and P. CPL mulch suppressed weed growth so that after two years weed abundance was only 27% weed cover compared with 86% for the commercial fertilizer-treated plots. Six weeks after treatment, soil N was five times higher in soil treated with commercial fertilizer than with CPL mulch, indicating that N release to the environment was not a problem with CPL. However, 47 weeks after treatment, the soil from plots with the CPL mulch had twice as much water-soluble P as soil treated with commercial fertilizer. High applications of CPL could elevate P in surface runoff to levels that cause environmental degradation. Results indicate that CPL could be used as a weed suppressant without adversely affecting nitrogen release to the environment. However, P concentration in soil water may be problematic.
Technical Abstract: Proper management of poultry manure and bedding (litter) can prevent environmental degradation such as hypoxia in aquatic communities. 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. Plots beneath peach trees (Prunus persica L. 'Sunhigh') all received preemergence herbicides and then the following treatments in May 1998: commercial fertilizer (15 g N m-2), low rate CPL (15 g N m-2 as 2.9 kg CPL m-2), high rate CPL (62 g N m-2 as 11.6 kg CPL m-2), and no fertilizer or mulch control. Weeds were completely controlled by mulch and herbicide during 1998 but, during 1999, weed abundance increased. By September 1999, the high rate of CPL had only 27% weed cover compared with 86% for the commercial fertilizer-treated plots. In plots treated with commercial fertilizer, soil N was highest (16.4 mg NH4-N and 18.6 mg NO3-N kg-1 soil) 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 3.2 mg NH4-N and 0.7 mg NO3-N kg-1 soil at six WAT. Water-extractable P (WEP) in the soil did not differ among treatments at 6 WAT (approximately 12 mg P kg-1 soil for all treatments). However, at 47 WAT, plots with the high rate of CPL had significantly higher WEP, 30 mg P kg-1 soil compared with 14 mg P 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 litter- and fertilizer-treated plots (averaging 45 mg P kg -1 soil). MEP was lowest in control plots (averaging 21 mg P kg-1 soil). Results indicate that CPL could be used as a weed suppressant without adversely affecting nitrogen release to the environment. However, P concentration in soil water may be problematic.