Herbicide Efficacy in Alternative Substrates forContainer-grown N ursery Cropsl

Diana R. Cochran2, Charles H. Gilliam3, Glenn Wehtje{, Glenn B. Fains, Robert D. Wright6, and Cheryl R. BoyerTDepart me nt oJ' Hort icu lture

Auburn Universitv. Auburn. AL 36849

AbstractThree experiments were conducted to evaluate the influence ofalternative substrates on herbicide efficacy in container grown nurserycrops. In Experiment l, alternative substrates evaluated were either pine wood chips hammer-milled, to pass between 0.48 cm (0.19in) screen (PWCHI) or 0.64 cm (0.25 in) screen (PWCH2), whole pine trees chipped or hammer-mil led (WTCH), to pass betweena 0.48 cm (0.19 in) screen, orthe previously mentioned combined with pinebark. A commercial pine bark substrate (PB) with a 6: l(by vol) ratio of pine bark to sand was maintained as a control treatment. Rout@ at 3 lbs aia (oxyfluorfen + oryzalin

^t2.24 + l.l2

kg'ha r) and Ronstar at 4.0 lb aia (oxadiazon at 4.48 kg'ha r) were applied at recommended label rates. Herbicides were applied andirrigated, and each container was overseeded with 25 spotted spurge (Euphorbia maculota) seedper container. In general. the greatestspurge numbers occurred in PB substrates. Rout provided superior spurge control compared to Ronstar. In Experiment 2, substratesevaluated were PWCH2, WTCH and PBS with 7.0 kg'm r (12 lbs'yd r) of Polyon l7-6-12 or with an additional 8 lbs'yd r of Polyon17-6-12, or PWCH2 and WTCH combined with composted poultry litter (CPL). PWCH2 tended to have the fewest spurge numbersthroughout the experiment, while WTCH and PBS tended to have similar spurge numbers and spurge fresh weight. Addition of CPLand additional fertilizer tended to increase spurge numbers and spurge fresh weight in all substrates. Rout and Ronstar provided similarspurge control in this study. In Experiment 3, substrates evaluated were PB (100%), WTCH (100%), CCR (100%), and PB:S (6:lvol), WTCH:S (6: l vol), and CCR:S (6: l vol). Rout and Ronstar were each applied at0.25x,0.50x, 0.75x, and l .0x label rate. Therewas a significant substrate affect on all dates except 14 DAT. Spurge numbers and spurge fresh weight were greatest in PB or PB:Ssubstrates. Spurge numbers and spurge fresh weight in general decreased with increasing herbicide rates. At 45 DAT and 60 DAT,Rout had superior spurge control compared to Ronstar. With WT and CCR substrates, Rout provided excellent control (less than1.0 gram fresh weight) at the 0.50x and l.0x rates. In general, weed control in alternative substrates was superior to that obtained incommercial ly used pinebark.

Index words: weed control, nursery production.

Herbicides used in this study: Rout@ (oryzalin + oxyfluorfen) 3,5-dinitro-Na,Na-dipropylsulfanilamide + 2-chloro-l-(3-ethoxyl-4ni t rophenoxy)-4-( t r i f luoromethyl) benzene; Ronstar 2G (oxadiazon), {3- [2,a-dichloro-5-(1-methylethoxy)phenyl ] -5- l ( l , l -dimethylethyl) -1,3,4 - oxadiazol-2-(3H)-one).

Significance to the Nursery Industry

Recent research has focused on alternative substratesderived from forest products. While these substrates havebeen successfully used to produce a wide range ofcrops, noresearch has been conducted to evaluate the efficacy ofher-ticides used with these substrates. The objective ofthis studyras to evaluate the efficacy ofcommonly used herbicides onprostrate spurge control with alternative substrates, currentlybeing evaluated for container-grown nursery crop productionrc determine if current weed control practices will need tobe adjusted. These data show that control ofspotted spurger ith commonly used preemergence applied herbicides mayrtually be improved with some ofthe alternative substratesorrrently being evaluated.

Rccieved for publication March 26.2009; in revised form August 3,2009.fhrs research was supported in part by The Horticultural Research Insti-Erc. 1000 Vermont Avenue, NW Suite 300, Washington, DC 20005.

'former Graduate Research Assistant, Auburn University. Auburn, AL.!rrtj9. cochrdr@)gmai l.com

hofessor, Auburn University. Dept. of Horticulture, Auburn, AL 36849.gl l rc l@ auburn.edu

?rol'essor, Auburn University, Dept. of Agronomy and Soils, Auburn, AL.!dt-19. wehtjgr@auburn.edu

{ssistant Professor, Auburn University. Dept. of Horticulture, Auburn,1t i6849. gbf0002@auburn.edu

?rolessor, Virginia Tech, Dept. ofHorticulture, Blacksburg, VA 24061-il!l-. n rightr@vt.edu

tssistant Professor, Kansas State University, Dept. ofHorticulture, Man-Utan. KS 66506. crboyer@ksu.edu

J Environ. Hort. 28( l\:19-26. March 201 0

Introduction

In the past few years the supply of pinebark for use incontainer nursery crop production has decli ned ( I 2). Severalfactors have contributed to this decline including: use ofpinebark for fuel or increased in-field harvesting which leavesthe pine bark in the forest, and increased foreign importationof logs without bark (12). With l imited supply and increas-ing prices, there is greater interest in the use ofalternativesubstrates in container nursery crop production.

Many alternative substrates have been evaluated for con-tainer grown crops including: biosolids (6, 8, 9, l0), woodwaste (13), coco fibers (14), and pine tree biomass (2,5,l l,16, 20). ln 2004. Gruda and Schnitzler (7) had success ingrowing vegetable transplants in spruce wood chips. Boyeret al. (2) reported that perennials grown in clean chip residual(forestry by-product of in-field harvesting) were similar toplants grown in pinebark. Fain et al. (5) evaluated a substratemade from all above ground portions of loblolly pine, wholetree (WT). Plants grown in WT were similar in size to thosegrown in traditional pinebark substrates. Wright and Browder(20) demonstrated that Ilex crenatq'Chesapeake' could begrown effectively in ground loblolly pine logs.

While these substrates have been evaluated for container-grown crops, limited research has been done with alternativesubstrates to determine if herbicide efficacy is affected.Preemergence herbicides are the most common method ofweed control in container nurseries (4). Herbicides are ap-plied to and adsorbed by the substrate and it must be desorbedinto solution for uptake by the weed (3). Many of the alterna-

l9

tive substrates contain higher wood content than traditionalpine bark based substrate. Impact of high wood content sub-strates on herbicide adsorption is unknown; however, othercultural practices have been impacted by these substrates. Forexample, Wright and Browder (20) demonstrated electricalconductivity (EC) was lower in crops grown in pine woodchips and additional fertilizer was required in order to havesimilar growth to crops grown in pine bark.

Euphorbia maculata (spotted spurge) was selected asweed species to use in comparing herbicide efficacy withseveral alternative substrates. Spurge is a common summerannual weed that germinates quickly (18) causing a majorweed problem throughout the United States. The objectiveof this study was to compare herbicide efficacy on controlof spotted spurge grown in alternative substrates comparedto a traditional pine bark substrate.

Materials and Methods

Experiment L Nine substrates were evaluated forherbicideefficacy in container grown nursery crops: pine wood chipsC 95% wood) hammer-milled to pass a 0.40 cm (0.16 in)screen (PWCHI), pine wood chips hammer-milled to pass a0.64 cm (0.25 in) screen (PWCH2), whole pine tree chipped(WTC) [96% passed through a 5.0 cm (2.0 in) screen], WTC-hammer-milled to pass a 0.48 cm (0.19 in) screen (WTCH),PWCHI:pinebark (PB) (l: l by vol), PWCH2:PB (l: l by vol),WTC:PB (l: l by vol), WTCH:PB (l: l by vol), and PB:sand(6:1 by vol) (PBS). Substrates were amended with 7.1 kg'm'(12 lbs'ydr) of 11-6-12 (17N-2.6P-l0K), Polyon control-

release fertilizer (CRF), 3.0 kg'm 3 (5 lb'ydr) of lime, and0.9 kg'mr (1.5 lbs'yd-3) Micromax. Pour through extractionswere conductedat2l,56, and 85 days after potting (DAP) forpH and electrical conductivity (EC) (21). Substrate containercapacity, airspace, total porosity, and bulk density were de-termined with procedures described by Bilderback et al. (l).In general physical and chemical characteristics were withinacceptable ranges (22) (Table I ). On June 15, 2006, 10.2 cm (4in) containers were filled with substrate, watered in and thefollowing day two herbicides, Rout (oxyfluorfen + oryzalin at2.24 + l.l2 kg.ha-r) (3 lbs aia) and Ronstar (oxadiazon at4.48kg'ha-') (4 lbs aia) were applied. Non-treated controls weremaintained throughout the study. One day after herbicideapplication, each container was overseeded with 25 spottedspurge seed and placed in full sun with overhead impactirrigation. Data collected included spotted spurge numberat 30 and 60 days after treatment (DAT), and spurge freshweights at 60 DAT. Treatments consisted of a 9 x 3 facto-rial; 9 substrates and 3 herbicide treatments (Rout, Ronstar,and non-treated control). Experiment was conducted as acompletely random design with l0 single plant replicates.Data were analyzed using a generalized linear model withleast significant difference means separation.

Experiment 2. Materials and methods were similar toexperiment one with the following exceptions. Compostedpoultry litter (CPL) was added as a substrate amendment andwith one set of substrates the fertilizer rate was increasedto 11.8 kg'm 3 (20 lbs'yd 3). Test was initiated August 29,

Table l. pH, electrical conductivity, and physical properties ofalternative substrates, Expt. I and 2.

Airspace'pH'

21 DAPContainercapacityY (% vol)

Totalporosity'

Bulkdensity'

(g'cmt)Substrates Ratio/rrte 2I DAP, 85 DAP

Experiment IPWCHI'PWCH2.WTCqWTCHPPWCHI:PBPWCH2:PBWTC:PBWTCH:PBPBS"

Experiment 2PWCH2:CPL"WTC:CPL

t00%t00%100%l0006

l : ll : ll : ll : ll : l

6.Ofg'6.2ef6.7b6.4d6.4cd5.9g6.4cd,6.3de6.6bc

6.Oab5.9abc6. l a5.8bcd5.3e4.8f5.6cd5.2e5.6d

6.0ab6. la

0.3a0.3ab0.2c0.3ab0.2b0.3ab0.2bc0.2bc0.3a

0.3a0.3ab

48.2b29.6f29.6f36.2de48.4b41.2c28.6t36.3de38.5cd

54.0a33.5e

32. lde39.0c51.5a50.8a33.0d37.6c46. lb45.7b28.8e

30. I de45.rb

80.3bc86.8a8l . l bc86.9a8l .4bc78.8cd74.6d82.Obc67.2e

84.2ab78.6cd

0. lefg0. I efg0.2defo. lg0.2de0. l def0.2bc0. l fg0.3a

0.2bc0.2cd

6: l6: l

7.2a7.2a

'pH range was acceptable as reported by Yeager et al., 1997. Best Management Practicses Guide for Producing Container-grown Plants.rContainer capacity - (wet weight - oven dry weight): volume of the sample.

-Air space = volume of water drained from the sample: volume of the sample.

"Total porosity : container capacily + n11 spns..

'Bulk density after forced-air drying at l05C for 48 h (l g'cm r = 62.43 lb'fr).

'DAP = days after potting.

'PWCHI = pine wood chips (100% wood) hammer-milled to pass a 0.48 cm screen.

'Means (within a column) with different letters are significantly different. within substrates or herbicides according to Least Significant Difference test (a= 0.05).

'PWCH2 = pine wood chips hammer-milled to pass a 0.64 cm screen.cWTC = whole pine tree chipped.pWTCH : WTC-hammer-milled to oass a 0.48 cm screen..pgg: pinebark:sand.

^CPL = composted poultry litter.

20 J. Environ. Hort. 28( I ): I 9-26. March 2010

Table 2. Preemergence herbicide efficacy evaluated with alternative substrates, Experiment l.

Alternativesubstrates Ratio/rate 30 DATI 60 DAT

Fresh weight (gm)

60 DAT

Spurge numbef

PWCHI'PWCH2'WTC"WTCH'PWCHI:PB'PWCH2:PBWTC:PBWTCH:PBPBS.

HerbicideRoutRonstarNon-treated

Main EffectsSubstrateHerbicideInteraction

t00%100%100%100 Yo

l : ll : ll : ll : l6: l

3 lb/aia4lblaia

l .8abc"

l .6bc0.8cl .9ab2.0ab2.0abl .2bc1.9ab2.7a

0.2c0.9b4.2a

0.0130.0010.001

3.Oab2. lbc| .5c3.4a3.2a3.0ab2.9ab3.4a2.7ab

l .0ct .7b5.8a

8.7ab2.4f3.7ef9.0ab7.9abc4.3def5.7cde6.8bcd

10.7a

l .4c6.7b

I l .9a

0.0020.0010.401

0.00 r0.0010.001

'Spurge number per container overseeded at 25 seed per container.tDAT : days after treatment.

'PWCHI = pine wood chips (- 95% wood) hammer-milled to pass a 0.48 cm screen."Means (within a column) with different letters are significantly different, within substrates or herbicides according to Least Significant Difference test(c: 0.05).

'PWCH2 : pine wood chips hammer-milled to pass a 0.64 cm screen.

"WTC = whole pine tree chipped.

'WTCH = WTC-hammer-milled to pass a 0.48 cm screen.

'Substrates with pinebark added l:l (v:v).

'PBS = pinebark:sand 6:l (v:v).

2007. Substrates evaluated included: PWCH2, WTCH,PBS, PWCH2 + 12.5% composted poultry l i tter (CpL)[PWCH2:CPL (6:l by vol)], WTCH:CPL (6:l by vol), PWCH2incorporated with 7.1 kg.m-3 Polyon control release fertilizer(CRF) (PWCH2:CRF), WTCH:CRF, and PBS:CRF. Spurgenumbers were taken at 30 and 60 DAT and fresh weightswere taken at 60 DAT. The experimental design was similarto experiment l; treatments consisted of an 8 (substrates) x 3(herbicide) factorial with l0 replications. Data were analyzedusing a generalized linear model with Least Significant Dif-ference and Duncan's Multiple Range Test, o: 0.05 (19).

Experiment -1. Materials and methods were similar toexperiments one and two with the following exceptions. Sep-tember 14,2007, six alternative substrates were potted; PB,PBS, Whole tree (WT), WT:sand (v:v) (6:l by vol) (WTS),Clean Chip Residual(CCR), and CCR:sand (v:v) (6:l by vol)(CCRS). On September 17,2007,either Rout or Ronstartreat-ments were applied (0.25x,0.5x, 0.75x, or l.0x label rate) andthe following day 25 spotted spurge seed were overseededper container on treated and control containers. Containers\r,ere placed in a double layer polyethylene greenhouse witha minimum temperature of 70F. Spurge numbers were takenat l5, 30, 45, and 60 DAT and weed fresh weights were takenat 60 DAT. Rout and Ronstar treatments consisted of a2 x 6x 5 factorial with 6 single pot replications. All experimentswere conducted at the Auburn University Paterson Green-house Complex, Auburn, AL. Data were analyzed using ageneralized l inear model with a : 0.05.

J. Environ. Hort. 28( I ): I 9-26. March 2010

Results and Discussion

Experiment 1. At 30 DAT, spurge number was similarfor WTC, PWCHI, PWCH2 and WTC:PB with WTC. Thehighest spurge numbers tended to occur in substrates withPB. (Table 2). These trends continued at 60 DAT with WTChaving lower spurge number than any ofthe other substrateswith the exception of PWCH2. Lower spurge number in thesesubstrates could be a result of the large particle sizes, whichare not as conducive for weed germination (21). Richardsonet al. (17) reported reduced spurge number in large containers(# 7) when pine bark mini-nuggets were applied to a depth ofeither 1.5 or 3 inches. Spurge fresh weights (SFW) were 78 and6502 lower in PWCH2 and WTC respectively than PBS.

Overall, Rout provided superior spurge control throughoutthe study (Table 2). For example, spurge numbers were lessper container with Rout at 30 (77%) and 60 (41%) DAT andSFW were 79o/o less than containers treated with Ronstar.These results concur with previous rankings of herbicide ef-ficacy comparing Rout and Ronstar for spurge control (15).

Significant herbicide x substrate interactions occurredat 30 and 60 DAT. Substrates treated with Rout had simi-lar spurge control at 30 and 60 DAT compared to the PBSsubstrate (Table 3). All substrates treated with Rout hadsimilar SFW compared to the commercial substrate (PBS)with the exception of WTCH. Ronstar applied to PWCH2,WTC, and WTC:PB had less spurge number compared tothe commercial substrate (PBS) at 30 DAT. Similarly spurgefresh weights were reduced by , 9g (PWCH2), 58 (WTC),82 (PWCH2:PB), and 65% (WTC:PB) compared to the

2l

Table 3. Herbicide-substrateinterrction on spurgecontrolin alternrtivesubstrrteswith commonly used preemergence applied herbicides, Experi-ment l.

Alternativesubstrates

Rout Ronstrr Non-treated

Spurge numbeF Spurge number Spurge number FW

30 DAT' 60 DAT 60 DAT 30 DAT 60 DAT 60 DAT 30 DAT 6ODAT 6ODAT

PWCHI*PWCH2.WTCIWTCH.PWCHI:PB'PWCH2:PBWTC:PBWTCH:PBPBSC

0.0a"0.0al . laL0a0.0a0.0a0.0a0.0a0.0a

0.6bcd0.2cd0. ld2. lal.Oabcdl.6ab0.5bcdL4abcl. labcd

0.3b0. lb0. lb6.0ar .2bl .5bl . lbl . lbl .5b

0.9abc0.0c0.3cl.8ab0.8abc0.6abc0.4bcl . labcl .9a

2.5ab0.4c0.8bc2.7al.5abcl.6abc1.9abc2.4abl.6abc

' l.labc

0. ld5.5bcd8.5abc7.7abc2.4cd4.5bcd

l0.4ab13.0a

4.4 bc4.8abl . ld2.9c5.2ab5.3ab3.1c4.9ab6.2a

5.8ab5.6abc3.9c5.4bc7.3a5.9ab6.3ab6.7ab5.4bc

18.8a6.8e5.8e

12.6cdl4.9bc9.Ode

l l .6cd9.2de

I 7.5ab

'Spurge number per container overseeded at 25 seed per container.rFresh weight (grams).

"DAT: days after treatment.*PWCHI = pine wood chips (- 95% wood) hammer-milled to pass a 0.48 cm screen.

"Means (within column) with different letters are significantly different, within substrates or herbicides according to Least Significant Difference test (c= 0.0s).'PWCH2 - pine wood chips hammer-milled to pass a 0.64 cm screen.IWTC: whole pine tree chipped.

"WTCH - WTC-hammer-milled to pass a 0.48 cm screen.

'Substrates with pinebark added l:l (v:v).cPgg = pinebark:sand 6:l (v:v).

commercial substrate (PBS). Comparing non-treated sub-strates; PWCH2, PWCHI:PB, PWCH2:PB, and WTCH:PBhad similar spurge numbers compared to the commercialsubstrate (PBS) at 30 DAT. At 60 DAT spurge number percontainerwere similar in all non-treated substrates compared

Table 4. Infuence ofalternative substrstes on herbicide efficacy, Experiment 2.

to the commercial substrate (PBS), except those grown inPWCHI:PB, which had the highest spurge number. Spurgefresh weights were significantly less in PWCH2, WTC,WTCH, PWCH2:PB, WTC:PB, and WTCH:PB comparedto the commercial substrate (PBS).

Alternativesubstretes Ratio/rate 30 DATY 60 DAT

Fresh weight (gm)

60 DAT

Spurge numbef

PWCH2"WTCH'PBS,PWCH2:CPL'WTCH:CPLPWCH2:CR.F"WTCH:CRFPBS:CRF

HerbicidesRoutRonstarNon-treated

Main EffectsSubstrateHerbicideInteraction

100%looo6: l6: l6: l

100% + 20 tb cRF100% + 20 tb cRF

6: l

3 lb'aiat4lb.airt

0.4e"3.4ab2.2cdl .8d4.0al . l de2.3bcd3.2abc

0.8b0.9b5.2a

0.00010.00010.00t 8

0.6e3.3bc2.8bc2.Ocd) . )a

l .4de3.4bc3.8b

t.0br.3b6.2a

0.00010.00010.0001

0.3d0.9cd3.8abc5.8ab6.6a0.9cd3. I bcd5.8ab

t.2bt.5bI . ta

0.00010.00010.0001

'Spurge number per container overseeded at 25 per container.YDAT = days after treatment.

'PWCH2 = pine wood chips hammer-milled to pass a 0.64 cm screen.*Means (within a column) with different letters are significantly different, according to Least Significant Difference Test (a = 0.05).

'WTCH: whole pine tree chipped, hammermilled 3/8 in screen.

"PBS = pinebark:sand 6:l (v:v).

'CPL: composted poultry litter.

'Substrates with the addition of20 lb Polvon control release fertilizer.

22 J. Environ. Hort. 28( I ): I 9-26. March 2010

Table. 5' Herbicide-substrate interaction on weed control in alternative substrates with commonly used preemergence applied herbicides, Experi-ment 2.

Ronstar Non-treated

Spurge number' FW! Spurge number Spurge number

30 DAT' 60 DAT 60 DAT 30 DAT 60 DAT 60 DAT 30 DAT 60 DAT 60 DAT

FWAlternativesubstrates

PWCH2"WTC'PBS'PWCH2:CPL'WTC:CPLPWCH2:CRF'WTC:CRFPBS:CRF

0.0b'1.6ab0.0b0.5ab2. la0.0bl . lab0.8ab

0.0c2-4ab0.0c0.5c3. la0.0cl .4bcL0bc

0.0b0.8b0.0b0.7b4.6a0.0bl .3b2. lb

0.0bl .5ab0.6ab0. lb2.6al . lab0. lbl . lab

0.0c2.3ab0.7bc0.3c3.6al .6bcl . lbc0.6bc

0.0b0.8ab2.8ab0.2b3.5al .Oabl .4abz.Jat\

l . lc7.0a5.9a4.8ab7.4a2. lbc5.5a7.6a

l .9c5. lbc/ .JAn

5.4bc9.9a2.5c7.8ab9.8a

0.8cI .3c9.4abc

16.6aI l .7abl .7c7.0c

l3.Oab

'Spurge number per container overseeded at 25 seed per container.rFresh weight (grams).

'DAT: days after treatment.

"PWCH2 : pine wood chips hammer-milled to pass a 0.64 cm screen.

'Means (within a column) with different letters are significantly different, according to Least Significant Difference test (c : 0.05)'WTC : whole pine tree chipped.tPgg

- p inebark:sand 6: l (v:v) .

'Substrates with composted poultry liter 6:l (v:v).

'Substrates with the addition of20 lb.yd I polyon control release fertilizer.

Experiment 2. Throughout the experiment PWCH2 sub-strates tended to have the fewest spurge numbers and leastSFW (Table 4). Addition of CPL to PWCH2 increased spurgenumbers and SFW compared to PWCH2 alone. WTCHspurge numbers were slightly higher at 30 DAT than PBShowever, at 60 DAT were similar to PBS. SFW were greatestwhen grown in CPL substrates or PBS. Rout and Ronstar pro-vided similar spurge control throughout this experiment.

Significant herbicide x substrate interactions occurredwith each data set. At 30 DAT all substrates treated withRout were all similar compared to the commercial substrate(PBS) (Table 5). WTCH:CPL treated with Rout had grearerspurge number per container compared to the commercialsubstrate (PBS) at 30 and 60 DAT. All other substrates hadsimilar spurge numbers compared to PBS. Spurge freshweights were similar in all Rout treated substrates comparedto the commercial substrate (PBS) with the exception ofWTCH:CPL.

Table 6. Physical properties of alternative substrates, Experiment 3.

Similar to Rout, Ronstar provided similar control in allsubstrates compared to the commercial substrate (PBS),30 DAT (Table 5). At 60 DAT, Ronstar treated substratesprovided similar control to the commercial substrate (PBS)with the exception of WTCH:CPL, which had about 80%more spotted spurge than PBS. All Ronstar treated substrateshad similar SFW at 60 DAT compared to the commercialsubstrate (PBS), although those with PBS or CPL tended tobe higher. Ronstar treated substrates with PWCH2 tendedto have the least SFW. Comparing non-treated substrates;PWCH2 and PWCH2:CRF had fewer spurge per containerat 30 DAI compared to PBS. At 60 DAT, PWCH2, WTCH,PWCH2:CPL, and PWCH2:CRF had less spurge comparedto PBS. Fresh weights were less in PWCH2 and WTC whenCRF was added compared to PBS. Nitrogen (N) immobili-zation in high wood content substrates has been identifiedas one issue impacting growth of nursery crops. Similarly,spurge growth may be affected. When comparing PWCH2

Substrates Ratio

Containercapacity'

Airspace)

Totalporosity'

Bulkdensity"

(g'cm.)(%" vol)

PBPB:SWTWT:SCCRCCR:S

LSD'

100%6:l

100%6:l

100%6:l

44.6+t.)59.465.855.6

4.8

24.523.216.824.624.8

5.2

79.371.882.782.680.380.2

2.1

0.1 80.360.140.360. l60.37

0.01

'Container capacity : (wet weight oven dry weight) + volume of the sample.!Air space : volume of water drained from the sample + volume of the sample

'Total porosity : container capacity + aiy 5pags.

'Bulk density after forced-air drying at l05C for 48 h (l g.cm r : 62.43 lb.ft r)

'Least Significant Difference test (o - 0.05).

J. Environ. Hort. 28(l ): l9 26. March 2010 z)

Table 7. Main effects ofsubstrate data pooled over all rates and the non-treated, Experiment3.

Spurge number'

Alternative substrate Ratio/rate' 14 DAT* 30 DAT 45 DAT 60 DAT 60 DAT

Rate"I2J

/5

PB'PB:S'WTWT:S'CCRqCCR:SP

t00%6:l

t00%6:l

100%6:l

0.00x0.25x0.50x0.75x1.00x

3 lb'airr4 lb'aia I

2.5a"2.6a2.6al .7b2.3ab2.2ab

4.5a2.9bl .9cl .5c0.8d

0.12810.00010.12970.89r 30.42620.61660.4820

2.8ab3.4a2.2bcl .8c2.5bc2.2bc

5.5a3.2bl .7cl .4c0.6d

0.00050.00010.32920.805l0.39050.68460. l 505

3. lab3.5a2.6bcl .8d2.3cd2.5bcd

5.4a3.2b2.5cl .4d0.7d

0.00010.00010.24370.00140.98480.23260.163 I

3.5ab4. la2.8bc2.2c3.Obc2.8bc

5.8a3.3b2.1bc2.4c1.2d

2.4b5.ta

0.00030.00010.24580.00010.02710.86890.0568

21.6a23.2a0.8c0.5c7.4b3.Obc

22.7a8.6b8.8b6.3b0.8c

6.2b12.8a

0.00010.00010.00010.00010.00100.36980.0001

Herbicide - l.0x rateRoutRonstar

Main effectsSubstrateRateSubstrate x RateHerbicideSubstrate x HerbicideRate x HerbicideSubstrate x Rate x Herbicide

2.3b3.0a

2.4a2.5a

2.3a2.3a

'Spurge number per container overseeded at 25 seed per container.YFW: fresh weight (grams)

"Ratio/rate : ratio is either 100 o/o substrate or mixed with sand 6:l (v:v); rate is herbicide applied per

treatment based on label rate (Rout - 3 lb'aia r, Ronstar - 4 lb'aia r).

*DAT: days after treatment.

"PB: pinbark (100%).

"Means (within a column) are significantly different according to Least Significant Difference test (o: 0.05), Experiment 3.,tg'5 : pine bark:sand 6:l (v:v).

'WT - whole pine tree chipped.

'WT:S whole pine tree chipped:sand 6:1 (v:v).qCCR: clean chip residual.pCCR:S: clean chip residual:sand 6:1 (v:v).oPooled comoarison ofherbicide x rate data.

substrates, addition of CPL increased spurge fresh weightsby 95% while adding CRF increased spurge fresh weight by53%. WTCH substrates tended to respond similarly.

Experiment 3. Analysis ofphysical properties showed thatsubstrates containing WT and CCR had greater containercapacity than PB substrates (Table 6). Air space was similaramong all substrates except 100% PB which was highest.According to a pooled comparison over all rates and thenon-treated, no rate-by-herbicide interactions were detected(Table 7); however, there was a substrate effect at 30, 45, and60 DAT. At 30 DAT, PBS had the most weeds per container(3.4) compared to all other substrates with the exception ofPB (2.8). At 45 and 60 DAI PBS had more spotted spurge percontainer than Wl WT:S, CCR, and CCR:S. Fresh weightwas considerably less in all substrates (0.8 gm'container I

lWTl, 0.5 [WT:S], 7.4 [CCR], 3.0 [CCR:S]) compared to PB(21.6) and PBS (23.2). Additionally, as expected there wasa rate effect throughout the study. As rate of herbicide in-creased spotted spurge number decreased. At 60 DAT therewas a substrate x rate effect in SFW. Rout and Ronstar had

24

similar control at 14 and 30 DAI however at 45 and 60 DATRout had better spurge control. There was also a substrate xherbicide effect at 60 DAT (weed number and SFW) and asubstrate x rate x herbicide effect at 60 DAT (SFW).

Comparing substrates within rates showed spotted spurgenumbers tended to be less in substrates with higher woodcontent (Wl WT:S, CCR, CCR:S) (Table 8). In the non-treated substrates, spurge numbers were generally similarthroughout the study, with the exception of WT:S at 14,30and 60 DAT. Spurge fresh weights in non-treated substrateswere greatest in PB or PBS substrates.

Rout applied at 0.25x rate to all substrates at 14, 30, and45 DAT had similar spurge numbers (Table 8). However at60 DAT PBS had more spurge number per container (4.5)compared to CCR (1.0) and CCR:S (1.7). SFW was 93 and97%o less in WT and WT:S compared to PBS at 60 DAT.In CCR and CCR:S SFW was 99 and 93% less than PB:S.Rout applied at 0.5x had similar spurge numbers at 14 and30 DAT in all substrates. At 45 DAT WT (0.8) and WT:S(0.8) had 79o/o less spurge number per container and CCR(0.2) had 95% less compared to PBS (3.8). Additionally at 60

J. Environ. Hort. 28( I ): I 9-26. March 2010

Table 8. Evaluating rates ofRout and Ronstar in alternative substrates, Experiment3.

Spurge numbef Spurge number

14 DAT* 30 DAT 45 DAT 6ODAT 6ODAT 14 DAT 30 DAT 45 DAT 60 DAT 60 DAT

Qx PB"PB:S"wT'WT:S'CCR.CCR:Sq

LSDP

66.038.8

z.-)

2.534.66.3

zo.-'t

o.J

6.57.0o.J

5.85.3

-)-z

JO.l

6l .30.70.8

I 1.0t2.2

12.9

4.06.06.52.54.24.7

3.2

4.8o.z6.3z--t

6.55.2

-). -)

6.25.86.52.85.75.3

3.0

).n5.86.82.75.06.0

3.0

4.72.75.8) .2

5.7) .1

2.8

5.86.35.75.86.24.5

3.6

4.55.26.55.55.05.3

2.7

0.25x PBPB:SWTWT:SCCRCCR:S

LSD

10.015. I1.00.50.21.0

7.4

38.716.30.70.1

I J-Z

o.J

20.4

4.74.02.O2.54.75.7

2.6

3.53.83.53.7z.)3.3

2.2

J.J

1.53.33.0i .J

5.2

2.6

3.7-) --t

J.Z

).2

2.22.0

2.7

2.54_)

3.02.81.01.7

z.J

2.7z-J

2.04.02.7

2.6

4.53.0l - )

l --l

3.8+.J

2.5

3.83.52.81.84.04.5

z.J

)n2.70.7t .20.81.5

2.4

1.5AA

J.+

1.2t .71.7

2.2

1.75.21.60.81.00.8

5.8

5.5+.o1.52.02.2

5.8

- l -J

6.3- t . -)

2.7- t . J

2.5

2.7

10.259.92.20.14.52.9

I 1.8

2.5 2.5 13.31.8 4.0 I0.50.8 1.3 0.20.8 0.8 0.20.2 0.0 0.02.7 2.8 0.2

2.3 2.1 l l . l

,n2.80.8t .20.52.0

2.5

PBPB:SWTWT:SCCRCCR:S

LSD

0.5x

0.75 \ PBPB:SWTWT:SCCRCCR:S

LSD

)2. I

19.00.80.59.11.0

26.3

0;72.01.01.51.02.8

2.1

0.82.51.21;7t .J

1-2

2.0

0.72.7o.20.50.50.8

1.9

6.06.00.00.10.00.0

9.9

2.51.81.01.2l . )

0.8

J. l

3.52.30.00.31.70.3

2.7

2.72.70.8t .71.81.2

3.5- t .z

1.3t .56.81.3

f _( ,

2.02.81.22.01.0z.)

2.2

l .0x PBPB:SWTWT:SCCRCCR:S

LSD

0.7 l 8 3.2 3.10.8 2.0 3.2 5.60.3 0.3 0.8 0.00.3 0.3 0.5 0.00.3 0.8 1.8 Ll0.2 0.7 0.8 0.1

I .0 1.4 1.6 4.4

1.2 0.00.1 0.01.0 0.00.2 0.00.'/ 0.00.3 0.0

| . r 0.0

2.00.81.20.50.30.2

1.2

0.51.00.70.20.80.8

l .o

t .20.50.50.00.30.2

0.9

1.0t .00.70.50.80.3

l .J

'Spurge number per container overseeded at 25 seed per container.!FW: fresh weight (grams).

'Rate - amount of herbicide applied per treatment based on label rate (Rout - 0.25x - 0.75lb'aia ', 0.5x : 1.5 lb'aia 1,0.75x :2.25lb'aia r, LOx : 3.0 lb'aia r;

Ronstar:0.25x : 1.0 lb 'a ia L, 0.5x - 2.0 lb 'a ia ' , 0.75x :3.0 lb 'a ia ' , l .0x - 4.0 lb 'a ia ' ) ."DAT : days after treatment.

'pg - pine bark.,PB'S : pine bark:sand 6:l (v:v).

'WT: whole pine tree chipped.

'WT:S whole pine tree chipped:sand 6:1 (v:v).

'CCR: clean chip residual.qCCR:S = clean chip residual:sand 6:l (v:v).rLeast Significant Difference Test (o - 0.05).

DAT WT (1.3), WT:S (0.8), and CCR (0.0) had less spurgenumbers per container compared to PBS (4.0). Spurge FWat 60 DAT were similar when comparing substrates to PBS,which is the industry substrate standard. Rout applied at0.75x had similar spurge number at 14 and 30 DAT whencomparing the substrates to PB:S. However at 45 DAT, PB

J. Environ. Hort. 28(1):19-26. March 2010

(0.7), WT (0.2), WT:S (0.5), and CCR (0.5) had fewer spurgenumber compared to PBS (2.7). Spurge fresh weights weregreatest in PB substrate. Rout applied at0.75x or the recom-mended label rate generally provided similar control in allsubstrates regardless of DAT, with no FW difference in anyofthe substrates.

Ronstar applied at 0.25x rate provided similar control inall substrates throughout the study with the exception ofspurge fresh weight in PB (Table 8). When Ronstar was ap-plied at 0.5x rate at 14 and 30 DAT, all substrates had fewerspurge numbers per container compared to PBS with theexception of WT at 14 DAT. Spurge number at 45 DAT wereless in WT:S (1.5), CCR (2.0), and CCR:S (2.2) comparedto PBS (5.5). Spurge number and FW (60 DAT) was less inall substrates compared to PBS. When Ronstar was appliedat 0.75x rate spurge number and FW throughout the studywas similar among all substrates compared to PBS. Ronstarapplied at recommended label rate at 14 and 30 DAT hadsimilar spurge numbers per container regardless of substrate.At 45 DAT WT (0.3) and WT:S (0.3) had 85% less spurgenumber compared to PBS (2.0). Similar trends occurred at60 DAT with WT (0.8), WT:S (0.5), and CCR:S (0.8) havingless spurge number compared to PBS (3.2). Spurge freshweight was less in all substrates with the exception of PBwhen comparing the substrates to PBS. In general, spurgefresh weights were lowest throughout the study with WTor WTS. When Rout was applied, rates at 0.5x and aboveprovided acceptable spurge control in WT and WTS. Whilespurge numbers tended to be higher when Ronstar was ap-plied, the trend was similar in that WT and WTS substratesgenerally had the fewest spurge and lowest SFW WT hasabout 80% wood; CCR has about 50% wood; and PBS hasminimal wood. The higher wood content in these substratesappear to suppress spurge growth. In most cases, spurgenumbers were similar, however, SFWs were much lower inWT or WTS. Spurge growth in PB or PBS had the highesrSFWs regardless of herbicide rate or herbicide applied fol-lowed by CCR or CCR:S.

Generally, alternative substrates treated with Rout andRonstar had slightly fewer spurge numbers compared toPBS in all three experiments. Additionally, substrates withadded pinebark tended to have more spurge compared to non-amended substrates (Exp. 1). In experiment 2, spurge numberand fresh weights tended to be greater with PB or with theaddition of CPL. In experiment 3, non-treated containers hadsimilar spurge numbers throughout the study, respectively.However, 60 DAT SFW were significantly greater in PB andPBS compared to the other substrates. Overall in experiment3, Rout and Ronstar treated substrates, that contained a higherwood content, tended to have less SFW than PB and PBS.These data show that control ofspotted spurge may actuallybe improved with commonly used pre-emergent appliedherbicides on some alternative substrates.

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26 J. Environ. Hort .28( l) :19-26. March 2010