Subtropicl Plnt Science, 59:95-103.2007 Use of Fbric nd Plstic Brriers to Control Weeds in Blckberries D. J. Mkus U.S. Dept. Agriculture, Agriculturl Reserch Service Weslco, TX 78596 ABSTRACT Weed control in blckberries (Rubus spp.) is serious problem for orgnic producers nd those who wish to reduce their relince on herbicides. Three lndscpe fbrics (Dewitt, Texel, nd white polyester weve) nd one industril grde white on blck plstic were used for weed control in conjuction with newly plnted Kiow root cuttings in Feb. 2006. In the no-fbric tretment, weeds were controlled mechniclly by hnd. The reflectnt white plstic nd weve weed brriers reduced mid-summer soil tempertures t 10 cm nd reduced the mgnitude in soil temperture fluctution. None of the weed brriers hd n effect on soil wter content mesured t 0 to 20 cm. Plnt vigor nd height were improved by use of weed brriers. White plstic improved the cumultive seson yield by 30% in 2007 compred to other brriers or bre soil. Fruit from bre soil plnts showed the gretest decline in verge fruit size during the picking seson. Fruit from plnts grown in bre soil were lowest in soluble solids nd sugr:cid rtio compred to fruit from weed brrier tretments. Fruit grown over white plstic hd the highest men soluble solids nd sugr:cid rtios; both reflectnt weed brriers improved berry nthocynin levels. Additionl Index Words: Rubus spp., nthocynins, weed brriers, white plstic, orgnic weed control Mention of proprietry product does not constitute endorsement or recommendtion for its use by the U.S. Dept. of Agriculture. About 7,160 h of blckberries (Rubus spp.) re grown in North Americ (Strik et l., 2007). Severl cultivrs hve been reported to be dpted to south Texs (Lukefhr nd Scott, 1994). Weeds re the mjor culturl pest, prticulrly becuse of the long growing seson in the Rio Grnde Vlley. Weed control by non-chemicl methods would be highly desirble from both n environmentl nd orgnic mrket stndpoint. Numerous lndscpe fbrics, though expensive, re effective weed brriers. Becuse of the high vlue of the fruit nd perennil nture of blckberries, weed brriers hving severl yers of field utility would be desirble for weed control in both blckberries nd similrly-grown cne fruits. The objective of this study ws to evlute severl of these fbric mterils nd n industril strength white plstic for the control of weeds during the first fruiting yer of the thorny, erect, cultivr Kiow. MATERIALS AND METHODS Four mterils were tested: Dewitt (BWI, Shullenberg, TX) is blck polypropylene with polyester blend; Texel (BWI) is blck (gry on the other side) polypropylene / polyester permeble membrne; white-on-blck UV-stbilized polyethylene weve (PAK Unlimited, Corneli, GA); nd nylon-reinforced white on blck plstic (T-65, Reef Industries, Houston). The first three mterils llow ir, wter nd vpor exchnge, while the fourth does not. A soil only tretment ws included, which ws kept weed-free t monthly intervls. Mteril objective color (lightness, chrom nd hue), including tht of the bre soil t two soil moisture conditions, ws determined with Minolt Model 200 Chrom meter. The plnting site ws locted ner Monte Alto, Texs (Lt. 26º 26 N, Long. 97º 58 W) on Hrgill fine sndy lom (Fine-lomy, mixed, hyperthermic Udic Pleustolls) soil. A single 91 m row ws rotovted to 15 cm, 20 mil bi-wll irrigtion tpe plced 46 cm deep, nd two similr 0.6 m wide strips of ech brrier mteril plced prllel nd 23 cm from the row center to llow for the blckberry roots (15 to 20 cm in length) to be plnted 5 cm deep nd 0.6 m prt in-the-row. Fbric instlltion nd plnting were done on 2 Feb nd 15 Feb 2006, respectively. After shoot emergence, 10 cm 95
Subtropicl Plnt Science, 59:95-103.2007 of bgsse were plced over the 0.5 m-wide bre soil between the weed brrier tretments on 29 Mr. Ech 3.6 m experimentl plot consisted of 6 plnts, nd ech of the 5 weed control methods were replicted 5 times s rndomized complete block design. A 3 m width of grss sod ws on either side of the 25 plots. In repliction two, thermocouples were plced on 9 My on the south side of the row nd in the middle of the respective weed brrier nd corresponding soil only loction. The thermocouples were set t depth of 10 cm nd tempertures recorded hourly with CR- 10 dt logger (CSI, Logn, UT). Ten 20-cm long EC-20 moisture sensors (Decgon Devices, Pullmn, WA) were instlled verticlly from the soil surfce in the center of ech tretment in replictions two nd four on 7 July nd soil wter content ws mesured six times between 18 July 2006 nd 10 Jn. 2007. On 20 June 2006, 22 kg N / h (s 15-35-15) ws pplied to ll tretments through the irrigtion system. On Aug. 2, 0.62 kg of S.T.E.M. (Scotts, Mrysville, OH) soluble trce elements ws dded. On 6 Apr 2007, t initil flowering, 1 t poultry litter (50 kg N / h equivlent) ws pplied. Averge plnt height nd plot vigor (scle: 1=poor to 5=highest vigor) rtings were mde on 17 Oct 2006 nd 22 Jun 2007. Primocne pruning cuts were mde to keep plnt height to pproximtely 75 to 90 cm, mintin plot integrity, nd to remove triling type cne growth throughout the growing seson. In 2007, fruit ws hrvested on 15 My, 21 My, 24 My, 29 My, 5 Jun, nd 12 Jun from 1.8 m of row. Hrvested fruit were plced into 1 L clm-shell plstic continers nd plot yield determined. Just prior to the beginning nd fter the finl hrvests, 25 fruit per plot were collected to determine verge fruit weight nd to mesure fruit qulity prmeters. After weighing, fruits were stored t -20C until used. Fruit qulity. Approx. 70 g of fruit were blended, then vcuum filtered through Whtmn #3 pre-filter, followed by Whtmn #1 filter for 10 min. The filtrte volume ws mesured, then subsmples were used for soluble solids determintion (Atgo PR-32α digitl refrctometer), initil ph nd titrtble cidity (Mettler DL 12 titrtor). Totl nthocynins (s cynidin-3-glucoside) were estimted by spectrophotometry t 520 nm in 0.01% methnolic HCl (w:v). Dt were nlyzed by SAS Version 8.2 using the PROC GLM nd MIXED procedures (SAS Institute, 1999). The Ryn-Einot-Gbriel-Welsch multiple rnge test ws used for men comprisons t the pproprite probbility levels shown in the tbles nd Fig. 3. Differences between response mens in Fig. 4 were tested using the PDIFF option of the LSMEANS sttement of PROC GLM. Single degree orthogonl contrsts were mde between no-fbric nd ll fbrics nd between white plstic nd other tretments. RESULTS AND DISCUSSION The initil cost of the fbric mterils (FOB fctory) re given in Tble 1 long with their objective color properties of L (lightness), chrom (color intensity), nd hue (color). The L vlue is the most importnt ttribute in terms of soil cooling nd light reflectnce into the cnopy. White weve nd white plstic hd the highest L vlues. Soil L vlues were higher thn the Dewitt (blck) but lower thn the Texel (blck) fbrics. All fbrics, except white weve, pper to be durble enough to lst t lest one growing seson. The white weve begn decomposing fter bout 1 yer in the field. The locl erytheml (UV) index is typiclly 11 during the summer months. In compnion study, the Dewitt nd white plstic mterils hve withstood UV degrdtion fter two yers in the field (Mkus nd Jifon, 2007). The use of Tble 1. Cost, durbility fter one yer s use, nd differences in objective color (CDM) ttributes (P<0.01) of fbric mterils nd soil used. Initil cost CDM Vlue ($ / ft²) Durbility L Chrom Hue None 0.00 NA 41.6 c 14.3 73.0 c Texel (blck) 0.13 +++ 54.0 b 1.7 b 76.1 c Dewitt (blck) 0.15 +++ 25.5 d 1.5 b 64.9 d White plstic 0.15 +++ 85.0 1.7 b 240.3 b White weve 0.07 + 81.6 1.7 b 253.3 96
the bgsse-mulch strip suppressed, but did not eliminte ll weed growth. Projected brrier mteril instlltion costs would be comprble to tht of lying two double 0.6 m rows of plstic, which in our cse, were on 3.65 m row centers. In 2006, men weekly mid-summer soil tempertures t 10 cm were reduced by the lighter textured fbrics, white weve nd white plstic, nd incresed by the Dewitt nd Texel fbrics compred to the bre soil tempertures (Fig. 1.). This temperture pttern ws less pronounced in 2007, prticulrly s the white weve fbric begn to deteriorte nd the white plstic becme covered with soil (Fig. 2.). In 2006, men mid-summer weekly temperture devitions were reduced by fbrics, prticulrly the light textured fbrics, compred to those of the bre soil. Differences in men weekly stndrd devitions becme less pprent by mid-2007. Cne growth over the thermocouple loctions were not lwys removed in timely fshion, perhps contributing to mesurement inccurcies. Soil wter content in the 0 to 20 cm zone, which were mesured six times between Jul 2006 nd Jn 2007, showed no consistent pttern between tretments (dt not shown). Phenologicl development, bsed upon plnt height nd vigor rting, ws different between the soilonly nd fbric-grown blckberry plnts (Tble 2.). There were dte but no dte by fbric interctions. Hnd weeding removl time per plot ws significntly reduced with the use of weed brriers. In 2007, the first fruiting yer, tretment yield differences occurred on four of the six hrvest dtes (Fig. 3.). On every hrvest dte, blckberries grown over white plstic weed brriers hd the highest men hrvest weights. Bre ground plots hd the lowest men yields for the first four hrvests. Cumultive seson yield ws significntly higher (P<0.02) from blckberries grown on white plstic compred to ll other tretments (Fig. 3. inset). The 2007 experimentwise verge yield ws 5.8 t / h. Shorter hrvest intervls would hve improved totl yields cross ll tretments. Bsed on previous blckberry reserch in South Texs (Lukefhr nd Scott, 1994), we cn expect the 2008 or second fruiting seson yields to be higher. Men fruit weight ws not ffected by fbric use t the beginning of the picking seson (Tble 3.). Fruit from plnts grown without fbric hd the lowest men berry wt. (P<0.06) t the end of the seson nd hd the lowest (P<0.07) verge seson weights. Seson weight reduction ws lso gretest in blckberries grown without fbrics (P<0.12), which declined by 36% between the first nd lst hrvest. There were seson differences (P<0.01) in severl fruit rw qulity ttributes (Tble 4.). Lte-hrvested compred to erly-hrvested fruit were 19% lower in soluble solids, 17% lower in titrtble cidity (s mlic Subtropicl Plnt Science, 59:95-103.2007 97 Tble 2. Blckberry plnt height nd vigor rtings tken on 17 Oct. 2006 nd 22 June 2007 nd weed removl times (WRT) per plot in seconds (s). There were no weed brrier X dte interctions. Plnt ht. Vigor WRT (cm) score z (s) Dte: 17 Oct. 06 52.2 b 4.0-22 Jun. 07 64.5 3.9 - ** Y NS Weed brriers: None 52.4 b 3.5 b 210 Dewitt (blck) 59.7 4.0 44 b Texel (blck) 59.2 4.1 30 b White plstic 61.4 4.1 20 b White weve 59.2 4.1 65 b 0.16 X * * Contrst: none vs. others ** ** ** Z Y X Scle: 1= lest to 5= gretest plot vigor. N, *, ** = not significnt or significnt t P=0.05 nd P=0.01, respectively. Prob. > F vlue. cid) nd 41% higher in totl nthocynins. A contrst of bre soil vs. other tretments indicted tht the bsence of fbric use resulted in fruit with the lowest soluble solids nd sugr cid rtio (P<0.01). A contrst between fruit grown under white plstic to the other tretments indicted tht fruit grown under white plstic hd the highest soluble solids nd sugr:cid rtio nd lowest initil ph. Bsed on contrst compring the white fbrics (weve nd plstic) versus other tretments, nthocynins were higher in fruit grown under the more reflectnt weed brriers (P=0.05, dt not shown). Initil ph vlues were lower (more cid) in the erly hrvested fruit. In erly hrvested fruit, fruit ph ws lowest in Texel nd no fbric compred to Dewitt nd white plstic tretments (Fig.4.). In lte hrvested fruit, initil ph vlues were significntly higher in white plstic- verses Dewittgrown fruit. Whether this is meningful interction will be re-visited in the 2008 fruiting seson.
Subtropicl Plnt Science, 59:95-103.2007 35 10 cm depth, 2006 Bre soil Dewitt (blck) Texel (blck) White weve White plstic Weekly Avg. Temperture ( o C) 30 25 20 15 150 200 Std. dev. of weekly 250 temperture 300 350 Julin Dte Std. Dev. (Weekly Temp.) 4 3 2 0 5/30 7/19 9/7 10/27 12/16 DATE Fig. 1. Men weekly soil tempertures nd their men stndrd devitions t 10 cm beneth the four weed brriers nd bre soil in repliction two from the week beginning My 12 nd ending December 29, 2006. 98
Subtropicl Plnt Science, 59:95-103.2007 Weekly Avg. Temperture ( ο C) 35 30 25 20 10 cm depth, 2007 Bre soil Dewitt Texel White weve White plstic 15 Std. Dev. (Weekly Temp.) 5 4 3 2 100Std. dev. of weekly 200 temperture 300 Julin Dte 1 0 2/9 5/20 8/28 12/6 DATE Fig. 2. Men weekly soil tempertures nd their corresponding stndrd devitions t 10 cm beneth the four weed brriers nd bre soil in repliction two for the weekly periods Jnury 7 to December 30, 2007. 99
Subtropicl Plnt Science, 59:95-103.2007 7 Y IE L D (t /h ) 2.0 1.5 5/15 5/22 5/29 6/05 6/12 C u m. Y ie ld (t/h ) 6 5 4 3 2 1 0 b b b b 1.0 0.5 0.0 b b b b b b b b HARVEST DATE Bre soil Dewitt (blck) Texel (blck) White weve White plstic 5/15 5/22 5/29 6/05 6/12 Fig. 3. Men yield seprtion of fruit grown under five weed control methods t six hrvest dtes (P=0.05). Inset: White plstic improved seson yield compred to other tretments (P=0.02). 100
Subtropicl Plnt Science, 59:95-103.2007 4 None Dewitt (blck) Texel (blck) White Weve White Plstic Initil Pulp ph 3 2 0 ef cde f def cd b bc b b 5 / 11 6 / 18 Hrvest Dte Fig. 4. Interction mens between hrvest dte nd weed control method for initil berry pulp ph (P=0.01). Tble 3. Effect of weed brriers on erly nd lte seson verge fruit weight (g). There ws no dte x weed brrier interction. Seson Seson fruit weight Weed brrier 5/11 6/18 verge reduction (%) None 8.85 Z 5.53 b 7.19 b 36.0 Texel (blck) 8.65 7.43 b 8.04 b 14.2 b Dewitt (blck) 9.60 8.84 9.22 7.6 b White plstic 8.96 8.11 8.54 9.8 b White weve 9.01 7.60 b 8.30 b 17.0 b Prob.> F vlue NS 0.06 0.07 0.12 Contrst: None vs. Others NS ** ** ** Z LSMEAN seprtion t the respective probbility level shown. NS nd ** = not significnt nd significnt t P=0.01. 101
Subtropicl Plnt Science, 59:95-103.2007 Tble 4. Rw product qulity of blckberry fruits picked t the beginning (11 My) nd end (18 June) of the 2007 hrvest seson. Soluble Titrtble Sugr:cid Anthocynin solids Initil ph cidity rtio pigments (%) (% mlte) ( mg/100g) Dte: 11 My 11.8 Z 3.24 b 1.32 9.16 1749 b 18 June 9.6 b 3.48 1.10 b 9.11 2463 ** ** ** NS ** Weed Brrier (WB): None 9.8 b 3.34 b 1.29 7.72 c 2135 Dewitt (blck) 10.6 b 3.34 b 1.29 8.38 bc 2014 Texel (blck) 10.9 3.33 b 1.17 b 9.81 1734 White plstic 11.5 3.43 1.11 b 10.56 2309 (WP) White weve 10.6 b 3.35 b 1.17 b 9.20 b 2339 Contrsts: ** ** 0.07Y ** NS None vs. others ** NS NS ** NS WP vs. others * ** NS ** NS Interction: Dte x WB NS ** NS NS NS z Men seprtion t the respective probbility level shown. NS, *, ** = not significnt, significnt t P= 0.05, nd P= 0.01, respectively. Y Probbility of greter F vlue. Mlic cid is the mjor orgnic cid in blckberries (Whiting, 1957) nd cynidin-3-glucoside composes 95% of ll the nthocynins in Kiow (Fn-Ching nd Wrolstd, 2005). The experiment-wise mlic cid levels reported for the first hrvest dte were identicl (1.32 vs 1.3% ±0.1) to those reported by Kfks et l. (2006) for Nvho, which ws relesed from the sme breeding progrm s ws Kiow. The potentil increse in fruit nthocynins gined by using reflectnt weed brriers would be desirble bsed on recent reports relting to the nti-tumor properties of cynidin-3-glycosides (Ding et l., 2006). About 5% of the remining nthocynin in Kiow is cynidin-3-rutinoside (Fn- Ching nd Wrolstd, 2005), which hs been found to selectively kill leukemic cells (Feng et l., 2007). The food industry lso finds blckberry juices, becuse of their intense pigment concentrtion, useful in product blending. 102
Subtropicl Plnt Science, 59:95-103.2007 CONCLUSIONS Weed brriers effectively reduced the time necessry to control weeds during the first seson fruiting of Kiow blckberries. The white plstic weed brrier improved totl yields compred to ll other brriers nd bre soil (control). Fruit qulity ws improved when white plstic ws used for weed control, compred to other weed control tretments. High soil tempertures nd their mplitude were reduced by the more reflective weed brriers. Brriers hd little mesurble influence on soil wter content t 0 to 20 cm but tended to promote more vigorous plnt growth. LITERATURE CITED Ding, M, R Feng, SY Wng, L Bowmn, Y Lu, Y Qln, V Cstrnov, B_H Jing, nd X Shi. 2006. Cynidin-3-glucoside, nturl product d erived fr o m b l ckberry, e x h ibits chemopreventive nd chemotherpeutic ctivity. J. Biol. Chem. 181:17359-17368. Fn-Ching, H-J nd RE Wrolstd. 2005. Anthocynin pigment composition of blckberries. J. Food Sci. 70:198-202. Feng, R, H-M Ni, SY Wng, IL Tourkov, MR Shurin, H Hrd, nd X-M Yin. 2007. Cynidin-3-rutinoside, nturl polyphenol ntioxidnt, selectively kills leukemic cells by induction of oxidtive stress. J. Biol. Chem. 282:13468-13476. Kfks, E, M Kosr, N Turemis, nd KHC Bser. 2006. Anlysis of sugrs, orgnic cids nd vitmine C contents of blckberry genotypes from Turkey. Food Chem. 97:733-736. Lukefhr, MJ nd AW Scott, Jr. 1994. Blckberry evlution nd production in the Rio Grnde Vlley. Subtropicl Plnt Sci. 46:13-15. Mkus, DJ. nd J Jifon. 2007. Impct of weed brriers on newly plnted pech trees. HortScience 42:456-457. (Abstrct) SAS Institute Inc., 1999. SAS / STAT User's Guide, Version 8, Cry, NC; SAS Institute Inc., 3884 pp. Strik, BC, JR Clrk, CE Finn, nd MP Bndos. 2007. W o r l d wi d e b l c k b e r r y p r o d u c t i o n. HortTechnology 17:205-213. Whiting, GC. 1957. The non-voltile orgnic cids of some berry fruits. J Sci. Food nd Agric. 9:244-48. 103