Vol. 54—2000 - NorthEastern Weed Science Society

WEED CONTROL AND MINERALIZATION OF NITROGEN AND PHOSPHORUS FROM
COMPOSTED POULTRY MULCH IN A WEST VIRGINIA PEACH ORCHARD
P.L. Preusch and TJ. Tworkoski'
ABSTRACT
Large amounts of poultry manure and bedding (litter) are generated and applied to farm
landin the easternU.S. Impropermanagementof manureandnutrientrunoffcan cause
eutrophicationandotherundesirablechangesin aquaticcommunities.Poultrywaste can be
convertedto a stableorganicfertilizerby composting. Compostedpoultrylitterhas been
incorporatedinto soil priorto plantingannualcropsbutsoil incorporationmay not bepractical
heneath fruit trees. Synthetic fertilizers are usually applied to the soil snrface each spring to
provideN forthe season'scrop. This experimentwas designedto determinethe effect of surface
application of poultry litter on peach tree growth and yield. The objectives were to detenrtine the
effect of two rates of composted poultry litter applied to a peach orchard on (I) N and P
concentrations in soil and peach leaves, (2) peach yield, and (3) weed abundance.
Peach trees (Prunus persica L. 'Snnhigh') were planted in March 1988 with a 5 by 5 m
spacing. A 3-m-widevegetation-freestripwas maintainedbeneaththe trees. Oneexperimental
unit consisted of a plot heneath one tree. In May 1998 all plots received I kg diuron/ha plus I kg
terbacil/ha and the follo~ 4 treatments were applied: commercial fertilizer (15 g N 1m' as
0.15 kg 10/10/10NIPIK 1m ), low rate poultry litter (15 g N 1m' as 2.9 kg composted litter 1
m'). high rate poultry litter (62 g N 1m' as 11.6 kg composted litter 1m'). and no treatment
control. Soil and peach leafN and P and weed abundance were measnred during 1998 and 1999.
Theexperimentwas a randomizedcompleteblockdesignwith5 single treeexperimentalunits
for a totalof20 experimental units.
Weeds were completely controlled during 1998 with the early-season herbicide
applicationandno differencesoccurredbetweentreatments.During 1999 whenno herbicide
was applied, the high rate poultry litter rednced the % ground area covered by weeds to 2, 9, 10,
23, and 27% in May throngh Septemher, respectively compared with 30, 40, 53, 81, and 86% in
May throngh Septemher, respectively for the commercial fertilizer-treated ,Plots. Weed weight in
Septemher 1999 in plots treated with high rate poultry litter was 330 g 1m . Weed weight in
plots treated with commercial fertilizer was 622 g 1m'. Plots treated with low rate of poultry
litter and control had high weedabundance, similar to plots treated with commercial fertilizer.
A1thongh fewer weeds grew throngh the high rate of poultry litter, weeds were large and would
require management in addition to poultry litter mulch.
Soil N was highest in plots treated with commercial fertilizer (16.4 ug N-N14 and 18.6
ug N-NO, per g soil, 6 weeks after treatroent) and did not differ among the remaining treatments
(in the high rate of poultry litter - 3.2 ug N-N14 and 0.71lg N-NO, per g soil, 6 weeks after
treatment).WatersolubleP in thesoil did notdifferamongtreatmentsat 6 weeks aftertreatment
(approximately 12 ug P per g soil for all treatroents). At 47 weeks after treatroent plots with the
high rate of poultry litter had 30 ug P per g soil compared with 14 ug P per g soil in plots treated
'Graduate Student, Dept of Biology, Hood College, Frederick, MD 21701 and Plant
Physiologist, Appalachian Fruit Research Station, ARS-USDA, Kearneysville, WV 25430.
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