Comparison of Charred and Uncharred Wood Aggregates in Horticultural Substrates

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SNA Reserch Conference Vol. 59 214 Comprison of Chrred nd Unchrred Wood Aggregtes in Horticulturl Substrtes Lesley A. Judd, Brin E. Jckson, Willim C. Fonteno, Michel D. Boyette, nd Michel R.

1 SNA Reserch Conference Vol Comprison of Chrred nd Unchrred Wood Aggregtes in Horticulturl Substrtes Lesley A. Judd, Brin E. Jckson, Willim C. Fonteno, Michel D. Boyette, nd Michel R. Evns Deprtment of Horticulturl Science, North Crolin Stte University Cmpus Box 769, Rleigh, NC 2766 Index Words: biochr, greenhouse medi, root growth Significnce to Industry: This work provides dditionl evidence of the potentil use of biochr in greenhouse substrtes for crop production. However, biochr cn be produced using different methods, tempertures, nd feedstock, which will ffect the chemicl nd physicl properties of the finl biochr product. Therefore, it is importnt to know nd mesure the conditions of producing biochr in order to understnd how nd why it ffects substrtes nd crop production. Biochr cn then lso be produced consistently, nd potentilly producing more consistent results with crop production. This study indictes tht biochr cn be mixed with pet similr to perlite nd produce substrtes with similr physicl properties. Chemicl nlysis reported wide ph increse fter the substrtes were limed, indicting tht there re properties of biochr tht will id in ph increse of pet substrtes nd could ffect ph buffering. Plnt root growth ws not negtively ffected by the presence of biochr in the substrte, further iding in the potentil use of biochr in substrtes for continer production. Nture of Work: Interest in using biochr for horticulturl purposes hs incresed substntilly in recent yers due to its potentil benefits, such s high crbon content nd nutrient holding/exchnging cpcity. Biochr lso hs the potentil to be locl nd renewble product, produced from wste products nd/or regionlly vilble mteril (8). There re mny prmeters tht ffect the end-product when mking biochr, including feedstock, prticle size of feedstock, burn temperture, nd time of pyrolysis/chrring. These fctors lter the physicl nd chemicl properties of biochr s well s how the biochr performs in soil or soilless substrtes. There is potentil for horticulturl use of biochr in soilless substrtes used for continer production of greenhouse crops (6); however reports of the influence of biochr on substrtes do not show consistent benefits. This could be due to the wide rnge of feedstock used to produce biochr, from orgnic wstes to penut hulls, which could lter nutrient composition in the finl biochr product. There is need to explore the impct of the vst rnge of biochr properties on their potentil use in greenhouse nd nursery continer production (1 ). Biochr hs potentil s substrte replcement for perlite, s both re lightweight nd porous, s well s potentil economic benefit (cost svings) since perlite is the most Continer Grown Plnt Production 18

SNA Reserch Conference Vol. 59 214 expensive (by volume) individul component in greenhouse/perennil substrtes.

2 SNA Reserch Conference Vol expensive (by volume) individul component in greenhouse/perennil substrtes. Reserch hs shown improved plnt growth when biochr (produced from citrus wood in chrcol pit) ws mended with coir nd tuff (4 ). Improved plnt growth ws lso reported when biochr (produced from hrdwood t commercil chrcol-production compny) ws dded to sphgnum pet (6). Incresed root growth ws reported when biochr ws mended with pet-bsed substrte (7), however quntifiction of incresed root growth in biochr mended substrtes hs not been published. Most reports using biochr do not provide sufficient dt on the processing nd repetbility of biochr production. To investigte the potentil of using biochr in greenhouse substrtes, biochr needed to be produced with known/mesurble prmeters so tht the end product is consistent. To investigte the effect of biochr on root growth, mini-horhizotrons were used to quntify nd observe root growth nd development (5). The objectives of this study were 1) to test the effects of biochr on substrte physicl nd chemicl properties, nd 2) test the effects of biochr mended substrte on plnt root growth using mini-horhizotrons. Loblolly pine trees (Pinus ted L.) were hrvested nd hmmer-milled to yield 6.35 mm (.25 in.) pine-wood-chips (PWC). A portion of this mteril ws reserved to test chemicl nd physicl properties, nd the rest of the mteril ws used to produce biochr t North Crolin Stte University. The biochr production system used in this study ws top-lit updrft gsifier (2). On 17 April 214, 1.5 m 3 (2 yd 3 ) of the PWC mteril ws loded into lrge gsifier rector using conveyor to insure level plcement of the mteril. The PWC mteril ws lit t the top inside the gsifier rector, nd then the rector ws quickly closed to control the gsifiction of the mteril. Combustion ws sustined by regulting the mount of ir entering from the bottom (96.2 ft 3 min- 1 or 2.7 m 3 min- 1 ) nd pssing up through the mteril. A vent t the top of the rector llowed combustible gs from the process to leve the system, nd this gs ws lit to reduce the mount of smoke produced. A temperture probe inside the rector mesured the internl temperture of the flme front nd resulting biochr s the front psses. The temperture of the flme front during this production ws 72 C (1328 F). The externl temperture of the rector ws mesured with n infrred thermometer (Westwrd #2ZB46, UK) to determine speed of the flme front nd to ensure the flme front ws, in essence, level. Once the flme front reched the bottom of the gsifier, the ir flow ws shut off nd compressed nitrogen gs ws then fed through from the bottom for 24 h, prevent ny flre up s the biochr cooled. Once cooled, the chr ws removed from the rector nd stored in 1.5m 3 (2 yd 3 ) industril bgs under shelter. The study ws executed on 14 My 214 in greenhouses t North Crolin Stte University, Rleigh, NC. Six substrtes were used: pet moss t 9% (v/v) mended with 1% perlite (PL), pine-wood-chips (PWC), or biochr (BC), nd pet moss t 8% (v/v) mended with 2% PL, PWC or BC. Substrtes were mixed on 12 My 214, nd ll substrtes were tested for initil ph nd then mended with dolomitic limestone t Continer Grown Plnt Production 19

SNA Reserch Conference Vol. 59 214 3.85 kg m- 3 (6.5 lb yd- 3 ) to chieve n expected ph of 5.8. The substrtes contining biochr hd beginning ph of 3.

3 SNA Reserch Conference Vol kg m- 3 (6.5 lb yd- 3 ) to chieve n expected ph of 5.8. The substrtes contining biochr hd beginning ph of 3.7, nd sufficient lime ws dded to those substrtes to rise the ph to n optiml level (5.8). On 14 My 214, eight mini-horhizotrons were divided in the center to seprte ech chmber nd llowed for different substrte to fill the chmber. Four mini-horhizotrons were divided nd ech chmber ws rndomly chosen to be filled with one of the 9:1 pet:ggregte (PL. PWC or BC) substrtes. The other four mini-horhizotrons were divided nd ech chmber filled with one of the 8:2 pet:ggregte substrtes. The mini-horhizotron chmbers were filled with n individul substrte nd the whole mini-horhizotron ws tpped three times, by lifting the mini-horhizotron 1 em (4 in.) from hrd surfce nd gently dropping, to settle the substrte. Mini-Horhizotrons were then filled to the top with substrte gin, to ccommodte for substrte settling which occurs fter initil irrigtion events in the greenhouse. Once filled, the divider ws gently removed, llowing for ech substrte to be united in the center, where one plug of tomto (Solnum /ycopersicum 'Rom') ws plnted. Twenty-four 1 em (4 in. di.) greenhouse continers were lso filled, four per ech substrte, to be used for substrte chemicl nlysis (ph nd EC mesurements). Tomto plugs were plnted in the center of the continers s well. Mini-Horhizotrons nd continers were plced in the greenhouse nd plnts in ech substrte were overhed wtered s needed depending on wether conditions, nd never showed symptoms of wter stress. Plnts were fertilized t ech wtering with 2 ppm nitrogen with Peters Professionl Pet-Lite Specil (The Scotts Co., Mrysville, OH). Root length mesurements (em) were tken on the three longest roots ppering on the cler side of ech chmber every 3 dys fter plnting (DAP) until 21 DAP. Ech chmber hs two mesureble sides giving sum of two chmber sides for ech substrte in one mini-horhizotron. Mesurements were tken by plcing trnsprent sheet (3M Visul Systems Division, Austin, TX) with.39 x.39 in. grid on ech fce, nd roots were mesured from the center of the mini-horhizotron to the end of the gridlines, which reched the end of the chmber. Once week, pour-through ws conducted on the continer-grown plnts to mesure the ph nd electricl conductivity (EC) of every substrte ccording to the pour-through extrction procedure (9) using Hnn ph/ec meter (HI 9811, Hnn Instruments, Ann Arbor, Ml). On 4 June 214, the study ws terminted nd shoots were removed t the substrte surfce in the mini Horhizotrons. The root blls in the mini-horhizotrons were removed nd the vrying substrte sections were crefully cut 5 em (2 in.) from the center, in order to determine root mss within the specific substrte in which it ws growing. Roots were then crefully wshed to remove substrte in preprtion for dry weight determintion. Both the shoots nd wshed root systems were dried t 7 C for 48 h. Dt were subjected to the generl liner model procedures, nd root length mesurements, ph nd EC ws subjected to regression nlysis (SAS Institute version 9.3, Cry, NC). Mens were seprted by lest significnt differences t P :::;.5. Physicl properties including ir spce (AS), continer cpcity (CC) nd totl porosity (TP) were determined for ech substrte blend t experiment initition using the North Continer Grown Plnt Production 2

SNA Reserch Conference Vol. 59 214 Crolin Stte University Porometer method (3). Properties were determined using three representtive smples of ech substrte.

4 SNA Reserch Conference Vol Crolin Stte University Porometer method (3). Properties were determined using three representtive smples of ech substrte. To determine prticle size distribution of the three ggregtes (PL, PWC nd BC), four smples of ech ggregte were dried t 15 C for 48 hnd plced in Ro-tp Shker (Model B, W.S. Tyler, Mentor, OH) fitted with seven sieves; 6.3 mm (.25 in.), 2mm (.8 in.),.71 mm (.3 in.),.5 mm (.2 in.),.25 mm (.9 in.), nd.16 mm (.4 in.) for five min. The smple from ech sieve ws weighed, nd prticle size ws expressed s percentge of the totl weight of the smple. Dt from physicl property nlyses were subjected to the generl liner model procedures nd mens were seprted by lest significnt differences t P:::;.5. Results nd Discussion: Chemicl nlysis of the substrtes reveled tht t 5 DAP, the ph for ll substrtes were bove 6.5 (Tble 1 ). The initil ph of the PWC nd BC ggregtes were 4.2 nd 7., respectively. When mking the substrtes, initil ph of the biochr substrtes ws similr to other reserch reports (6). Substrte ph ws mesured fter lime ws dded nd these ph vlues were pproximtely 5.8 for ll substrtes. Biochr ggregtes my contin bicrbontes tht will rise substrte ph (6), however there ws lrge increse in ph of ll the substrtes nd therefore this increse could be due to other fctors, such s the rection between the pet nd lime ddition. At 5 DAP, the ph of 1% BC nd PWC substrtes were higher thn the 1% PL (Tble 1 ). At 12 DAP, the 1% PWC substrte ws higher thn the other substrtes, nd t 19 DAP there were no differences mong the substrtes. The ph for the 2% substrtes ws only different t 12 DAP, when 2% PWC substrte ws greter thn the other substrtes. Electricl conductivity for both the 1% nd 2% substrtes incresed from 5 to 12 DAP, nd dropped lower t 19 DAP (Tble 1 ). Compring the PL nd BC substrtes, EC ws not different t ll mesuring dtes, indicting tht the biochr ggregte used ppers to hve no significnt nitrogen drwdown/tie-up. Substrte physicl properties indicte tht there re no differences mong the 1 % PL, PWC or BC substrtes for ll properties (Tble 2). For 2% BC substrte, there ws greter TP nd CC, with lower AS. This could be due to the greter mount of fines nd medium-sized prticles found in the biochr ggregte tht fill in pores in the pet nd lower AS nd rise CC (Tble 2). This indictes tht chrring process cused significnt difference in prticle size distribution; the process reduced the size of the lrger PWC prticles nd creted more medium nd fine BC prticles. 2% PWC substrte hd greter AS with lower CC, nd this could be due to the PWC ggregte hving lower mounts of medium-sized nd fine prticles. 2% PL hd lower TP compred to 2% BC, however for CC nd AS for the two substrtes were not different. Both PL nd BC ggregtes hd similr extr-lrge, lrge nd fine prticles, but BC hd greter mounts of medium-sized prticles thn PL. Replcing PL with BC in pet substrtes creted comprble physicl environments for the tomto plnts. In the substrtes with 9% pet mended with 1% PL, PWC or BC, tomto root lengths mesured from 3 to 6 DAP were not different (Fig. 1A). At 9 DAP, roots in the 1 % PL substrte were significntly longer thn roots in the other substrtes. At 12 Continer Grown Plnt Production 21

5 SNA Reserch Conference Vol DAP, roots growing in 1% PL nd PWC were significntly longer thn roots growing in the 1 % BC substrte. After 15 DAP, there ws no difference in tomto root growth mong the three substrtes. Although differences were observed in root growth mong the substrtes from 9 to 12 DAP, roots growing in 1% BC cught up in length to the other substrtes by the next mesurement dte. Dt from the dry weight nlysis indictes tht root growth ws not different mong the substrtes (Fig. 2A). By the end of the study (21 DAP), there ws no differences in root growth mong the substrtes, with root growth nd mss comprble between 1 % PL nd BC. In the substrtes contining 8% pet with 2% PL, PWC or BC, tomto root lengths show differences from 6 DAP until 21 DAP. At 6 nd 12 DAP, roots growing in 2% BC were significntly greter thn roots growing in the other substrtes (Fig. 1 B). At 9 nd 21 DAP, tomto roots growing in 2% PL nd BC were longer thn roots growing in 2% PWC. Dt from the dry weight nlysis indictes tht root growth ws not different mong the substrtes (Fig. 2B). There were observble differences in visible root growth long the sides of the mini-horhizotron, with greter root growth in 2% BC substrte compred to roots in the 2% PWC substrte. This could be due to the chrring process; the 2% BC substrte seemed to stimulte root growth. However, by the end of the study root mss in the substrte (not ll visible) ws similr mong the substrtes. Literture Cited: 1. Altlnd, J.E. nd J.C. Locke Biochr ffects mcronutrient leching from soilless substrte. HortScience 47: Boyette, M.D., J.A. Mcilek, nd B.P. Alston The rpid production of biochr. ASABE Annu. Inti. Mtg., Texs, 29 July -1 Aug Fonteno, W.C., C.T. Hrdin, nd J.P. Brewster Procedures for determining physicl properties of horticulturl substrtes using the NCSU Porometer. Horticulturl Substrtes Lbortory, North Crolin Stte University. 4. Grber, E.R., Y.M. Hrel, M. Kolton, E. Cytryn, A. Silber, D.R. Dvid, L. Tsechnsky, M. Borenshtein, ndy. Eld. 21. Biochr impct on development nd productivity of pepper nd tomto grown in fertigted soilless medi. Plnt Soil 337: Judd, L.A Rhizometrics: Novel Techniques to Observe nd Mesure Root Growth of Continer-Grown Crops. North Crolin Stte University, North Crolin. M.S. Thesis. 6. Northup, J.l Biochr s replcement for perlite in greenhouse soilless substrtes. Iow Stte Univ., Ames, M.S. Thesis O'Hr, R Students evlute bio chr in soil. Greenhouse Grower 31: Peterson, E Blck gold. Digger 57: Wright, R.D The pour-through nutrient extrction procedure. HortScience 21 : Continer Grown Plnt Production 22

6 SNA Reserch Conference Vol Tble 1. ph nd electricl conductivity (EC) of ll substrtes used in mini-horhizotron study. Dys fter plnting (DAP) Rtio 2 Substrte ph EC ph EC ph EC 9:1: PLY 6.6 bx b PWCW b BCV b :2: PL b 1.3 b PWC b BC b 6.8 b Rtio = pet substrte mended with PL, PWC or BC s specified percent rtios (v/v). YpL = pet mended with perlite. xmens seprted within columns by DAP nd rtio for chemicl properties distribution by Lest Significnt Difference (LSD), P s.5. Mens followed by the sme letter re not significntly different. wpwc = pet mended with pine-wood-chips, PWC is produced by chipping nd hmmer-milling (6.35mm or.25 in. screen) loblolly (Pinus ted L.) pine logs. vbc = biochr ggregte used in mking substrtes for this study; BC is produced by PWC gsifiction. Continer Grown Plnt Production 23

7 SNA Reserch Conference Vol Tble 2. Physicl properties of ll substrtes used in mini-horhizotron experiment nd prticle size distribution of the ggregtes mended in the substrtes. RtioY 9:1 8:2 Substrte PLU PWC 5 scr PL PWC BC Continer cpcit/ (% vol) b 62.9 b 71.2 X-Lrge (>6.3 mm).12 b b Physicl properties 2 Air spcew Totl porosit/ (% vol) (% vol) 6.36 b b b b 9.1 b b 2.5 b 91.7 Prticle size distributionq (% weight) Lrge Medium Fine (6.3>2. mm) (2.>.5 mm) (S.5 mm) 19.3 c b 4.39 b 2 Physicl properties dt were collected from three smples per substrte nd represented s mens. Anlysis performed using the North Crolin Stte University Prmeter method (Fonteno et l., 1995). YRtio = pet substrte mended with PL, PWC or BC s specified percent rtios (v/v). xcontiner cpcity = (wet weight- oven dry weight) -;.. volume of the smple. w Air spce = volume of wter drined from the smple -;.. volume of the smple. vtotl porosity= continer cpcity + ir spce. upl =pet mended with perlite. 1 Mens seprted within columns by rtio for physicl properties by Lest Significnt Difference (LSD), P s.5. Mens followed by the sme letter re not significntly different. 5 PWC = pet mended with pine-wood-chips, PWC is produced by chipping nd hmmer-milling (6.35mm or.25 in. screen) loblolly (Pinus ted L.) pine logs. rbc =pet mended with biochr, BC is produced by PWC gsifiction. qprticle size distribution dt were collected from four smples per ggregte nd represented s men percent by weight of the smples. Anlysis performed using Ro-tp Shker (Model B, W.S. Tyler, Mentor, Ohio) fitted with seven sieves; 6.3 mm (.25 in.), 2mm (.8 in.),.71 mm (.3 in.),.5 mm (.2 in.),.25 mm (.9 in.), nd.16 mm (.4 in.). Pp L =perlite ggregte used in mking substrtes for this study. Mens seprted within columns for prticle size distribution by Lest Significnt Difference (LSD), P s.5. Mens followed by the sme letter re not significntly different. npwc = pine-wood-chip ggregte used in mking substrtes for this study; PWC is produced by chipping nd hmmer-milling (6.35mm or.25 in. screen) loblolly pine logs. msc = biochr ggregte used in mking substrtes for this study; BC is produced by PWC gsifiction. Continer Grown Plnt Production 24

8 SNA Reserch Conference Vol A E 14 - s; 12 -C) s::::.s! - c:::: B E 14 - J: 12 -C) s:::: - 1 ~ 8 o:= 6 4 ~ 1 PL L*** - 1 PWC L*** -lr-1 BC L*** ~ 2 PL L*** - 2 PWC L*** 2 -lr-2 BC L *** Dys fter plnting Figure 1. Root length mesurements (1 em=.394 in.) of tomto (Solnum /ycopersicum 'Rom') plnts in mini-horhizotrons when grown in (A) 9% (v/v) pet mended with 1% of perlite (PL), pine-wood-chips (PWC) or biochr (BC) with error brs representing mens seprtion (?:5.5). (B) Root length mesurements of plnts in the mini-horhizotrons when grown in 8% (v/v) pet mended with 2% PL, PWC or BC, with error brs representing mens seprtion (P:::;.5). Letters next to substrte represent liner regression significnce; L *** represents significnt liner effects when P$.1. Continer Grown Plnt Production 25

9 SNA Reserch Conference Vol A -C) Ul.5 Ul cu E.4 ~ ".3 - :::.2.1 B.8.7 C).6 - ~.5 1 PL 1 PWC Substrte 1 BC cu E ~.4 " -.3 ::: PL 2PWC Substrte 2 BC Figure 2. Root dry mss of tomto (Solnum Jycopersicum 'Rom') plnts grown in mini Horhizotrons. (A) Root dry mss of plnts grown in 9% (v/v) pet mended with 1 % perlite (PL), pine-wood-chips (PWC) or biochr (BC). (B) Root dry mss of plnts grown in 8% (v/v) pet mended with 2% PL, PWC or BC. Mens seprted cross substrtes by rtio by Lest Significnt Difference (LSD; P ~.5), nd sme letter indictes mens re not significntly different. Continer Grown Plnt Production 26

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