800-organic fertilizer for greenhouse tomatoes

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HORTSCIENCE 44(3):800809. 2009.

Organic Fertilizers for Greenhouse

Tomatoes: Productivity and

Substrate MicrobiologyZhengli ZhaiCentre for Agricultural Resources Research, Institute of Genetics and

Developmental Biology, Chinese Academy of Sciences, Shijiazhuang050021, China Graduate University of the Chinese Academy of Sciences,

Beijing 100049, China

David L. Ehret1, Tom Forge, Tom Helmer, and Wei LinAgriculture and Agri-Food Canada, Pacific Agri-Food Research Centre,P.O. Box 1000, Agassiz, British Columbia Canada V0M 1A0

Martine DoraisAgriculture and Agri-Food Canada, Horticultural Research Centre, LavalUniversity, Quebec, Canada G1V 0A6

Athanasios P. PapadopoulosAgriculture and Agri-Food Canada, Greenhouse and Processing Crops

Research Centre, Harrow, Ontario, Canada N0R 1G0

Additional index words. compost, spent mushroom substrate, composted yard waste, swine

compost, organic liquid fertilizer, fish fertilizer, nematodes, FDA, EcoLog

Abstract. Organic fertilizer regimens consisting of combinations of composts (yard waste,swine manure, or spent mushroom substrate) and liquid fertilizers (fish- or plant-based)

were evaluated against conventional hydroponic fertilizers in two experiments withgreenhouse tomatoes grown in peat-based substrate. Crop yield and fruit quality were

evaluated and several assays of substrate microbial activity and community profiles(fluorescein diacetate analysis and EcoLog, values, nematode counts) were conducted.

Crops grown in 20% to 40% compost (yard waste or yard waste plus swine manure) plusa continuously applied liquid source of organic potassium (K), calcium (Ca), magnesium

(Mg), and sulphate (SO4) could not be sustained more than 1 month before nutrient

deficiencies became visible. Supplementation with a nitrogen (N)- and phosphorus (P)-containing plant-based liquid fertilizer at the point when plant deficiencies became

apparent subsequently produced yields80% that of the hydroponic control. In a secondexperiment, the proportion of mushroom or yard waste compost was increased to 50% of

the mix, and liquid delivery of K, Ca, Mgand SO4 plus either plant-based or fish-based N-and P-containing liquid feeds was started at the date of transplanting. In this case,organic yields equal to that of the hydroponic control (8.5 kg/plant) were observed in

some treatments. The most productive organic treatment was the mushroom compost

supplemented with a low concentration of the plant-based liquid fertilizer. In general,organic tomatoes had a lower postharvest decay index (better shelf life) than did the

hydroponic controls, possibly as an indirect consequence of overall reduced yield in thosetreatments. High concentrations of both organic liquid feeds resulted in lower yields as a

result of treatment-induced fusarium crown and root rot. In contrast to some previousstudies, those treatments showing fusarium crown and root rot also had the highest gross

microbial activity. Measures of gross microbial activity and numbers of microbivorousnematodes were higher (average of 37% and 6.7 times, respectively) in compost/organic

feed treatments than in the hydroponic control. Community physiological profiles of the

bacterial populations, on the other hand, did not differ between organic and hydroponictreatments. Nematode populations were significantly correlated with gross microbialactivity in the organic treatments.

Organic production methods encouragethe use of organic waste materials as sub-stitutes for chemical fertilizers. This may bean effective way to use the high volumes ofurban yard waste and waste organic materialsemanating from dairy, poultry, swine, orgreenhouse operations and is therefore of

potentially significant environmental value(Cheng et al., 2004; Mazuela et al., 2005).Chong (Chong, 2005; Chong and Purvis,2004) has developed recommendations for

use of a variety of waste and compostproducts in the nursery industry, some ofwhich could be applied to organic productionsettings.Amendingsoil or potting media withsome organic wastes can improve soil phys-ical properties with increased porosity andwaterholding capacity as well as improved

biological characteristics (Celik et al., 2004;Lee et al., 2004; Marinari et al., 2000).

Although a good deal of research has beenconducted on the use of organic waste in fieldvegetable production (Ball et al., 2000; Smithet al., 2001), relatively little has been donein greenhouse vegetable production. A fullrange of organic wastes, from municipal

wastes to agricultural residues, could poten-tially be used as compost feedstock, dependingon local availability and country legislationfor organic products. For example, composts

produced from several different types ofagricultural residues may be suitable materi-als for container media or in field soils(Martnez et al., 2005). Rippy et al. (2004)found that several combinations of vermi-compost plus organic liquid feeds producedyields similar to those of conventional hydro-

ponic treatments.Liquid fertilizers formulated for organic

agriculture are often made from organicwastes and can be applied as a foliar spray

or through drip irrigation lines as an alterna-tive to chemical fertilizer. Cheng et al. (2004)used a greenhouse tomato crop to recover

part of the nutrients from swine wastewater toreduce the risk of nitrogen (N) and phospho-rus (P) losses to the environment. Thishas proven to be a feasible and promisingalternative technology for converting swinewastewater into value-added product. Liedlet al. (2004) found that liquid effluent ofdigested poultry litter appeared to functionas well as a commercial hydroponic fertil-izer for tomatoes after balancing the formsof N (NO3/NH4) and supplementing withCa(NO3)2 and MgSO4. Abbasi et al. (2004)used fish emulsion in a peat mix to growradish and cucumber seedlings. The resultsuggested that fish emulsion had both nutri-tive value for plant growth as well as disease-suppressive properties and thus might beuseful for organic or conventional transplant

production.Organic residues act not only as a source

of nutrients and organic matter, but also mayincrease the size, biodiversity, and activity ofthe microbial populations in soil, therebyinfluencing structure, nutrient turnover, andmany other related physical, chemical, and

biological parameters (Albiach et al., 2000).Organic residues can differ substantially in

Received for publication 9 Jan. 2009. Accepted for publication 19 Mar. 2009.We acknowledge the financial support of the BC Greenhouse Growers Association Research Council andthe Matching Investment Initiative of Agriculture and Agri-Food Canada and the generous in-kind supportof All Seasons Mushrooms, Great Pacific Bioproducts, Technaflora Plant Products, and the Vancouvercomposting facility.We also gratefullyacknowledge the ChinaScholarship Council. The technicalassistance of GlennBlock isappreciated.Use of trade names does not imply endorsement of the products named nor criticism of similar ones notnamed.1To whom reprint requests should be addressed; e-mail [email protected].

800 HORTSCIENCE VOL. 44(3) JUNE 2009


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terms of their effects on soil or substratemicrobial activity and derived benefits likedisease suppression (Borrero et al., 2004;Hoitink and Boehm, 1999; Kannangaraet al., 2000; Litterick et al., 2004; Nobleand Coventry, 2005; Ntougias et al., 2008;Zinati, 2005). For example, Martnez et al.(2005) estimated microbial activity by fluo-rescein diacetate analysis (FDA) and foundthat microbial biomass was higher in com-

posted cork thin waste mixed with rice hulls

than in peat used in soilless strawberry pro-duction. Relatively little is known of therelationships among organic waste amend-ments, microbial activity, and overall pro-duction in the context of organic practices,especially with respect to containerizedgreenhouse production. Furthermore, to ourknowledge, there is no information availablecomparing the substrate microbial activity oforganic and hydroponic systems.

The objective of this study was to developmethods of producing organic greenhousetomato plants, which show the long-termhealth and productivity expected of hydro-

ponic plants. The emphasis was on using

fertilizers and byproduct organic materialsthat are available in enough supply to be usedin large commercial greenhouse operationsand in keeping with the organic philosophy,locally produced. The effects of composts andfertilizers on substrate biological activity, andthe relationships between biological activityand productivity, were also determined.

Materials and Methods

General crop information. Two experi-ments were conducted in 2008 at the PacificAgri-Food Research Center, Agassiz, BC,Canada (lat. 4915# N, long. 12146# W).

The first experiment involved a beefsteakcultivar and the second used a cluster culti-var. In each, seed was sown into 4-inch (10-cm)pots filled with a peat/perlite (4:1 ratio byvolume) mixture and transplanted at a densityof 2.75 plants/m2 into a 75-m2 (64-m2 grow-ing area) venlo-style greenhouse compart-ment where the trials were conducted. In allexperiments, the peatmoss was SungrowOMRI white course peat (Allies Wholesale,Abbotsford, BC, Canada) and the perlite(TerraLink Horticulture Inc., Abbotsford,BC, Canada) was medium grade. The green-house environment was computer-controlled(Argus Controls, White Rock, BC, Canada).Greenhouse temperature set points were 19 to21 C during the day and 17 to 19 C at night.Relative humidity was maintained between40% and 80% day and 35% and 70% nightusing ventilation and misting throughout thegrowing season. Plants were irrigated (ferti-gated) with fertilizer solution multiple timeseach day based on light sum, which rangedfrom 250 to 500 Wm2 (irrigation frequencywas low early in the trials to minimizeleaching but increased as the plants grew).Each irrigation event delivered%132 mL ofnutrient feed to each plant over 1 min throughtwo pressure-compensated drippers (4 Lh1

or 66 mLmin1). Leaching ranged from 10%

to 30%. Nightly irrigations occurred every 4to 6 h. Plants were pruned and trained ac-cording to commercial production practices(Anonymous, 1996) except that stem densitywas not modified through the growing season.Fruit were harvested three times per week.

Expt. 1. Seeds of the beefsteak cultivarRapsodie (Rogers/Syngenta Seeds, Boise,ID) and the rootstock, Maxifort (deRuiterSeeds, Bergschenhoek, The Netherlands)were sown on 2 Jan. Maxifort is resistant to

Verticillum sp., Fusarium oxysporum races 1and 2, Fusarium oxysporum fsp. Radicis-lycopersici (crown rot), most common spe-cies of plant-parasitic nematodes, and Pyre-nochaeta lycopersici (corky root). Graftingtook place from 22 to 25 Jan. Plants weretransplanted into15-Lpots (h= 23cm, w = 31cmat the top)(one plant per pot)on 26Feb.inthe experimental greenhouse compartment.

Two composts were compared in thisexperiment: yard waste (YW) compost andswine (Sw) compost. Yard waste compostwas produced by the City of VancouverGreen Waste Recycling Program. It is a ClassA compost produced according to British

Columbias Organic Matter Recycling Reg-ulation (Government of British Columbia,

2007) using feedstocks consisting solely ofyard waste and lawn clippings. Certifiedorganic swine compost was obtained fromGelderman Farms, Abbotsford, BC, Canada.Mineral analysis of the composts is detailedin Table 1. Four substrates or combinationsofsubstrate were compared, all with a base of

peat/perlite: 1) peat/perlite (control); 2) 20%yard waste compost; 3) 40% yard wastecompost; and 4) 20% swine compost plus20% yard waste compost. All mixes were

blended on a volume/volume basis.Three liquid feeds were also tested: 1) a

standard hydroponic tomato feed; 2) organicfeed A consisting of potassium (K), calcium(Ca), magnesium (Mg), and sulphate (SO4)derived from organic potash, calpril, anddolopril (Terralink Horticulture Inc., Abbots-ford, BC, Canada) at concentrations similarto the standard hydroponic feed; and 3)organic feed B, consisting of organic feed Asupplemented with a blend of commerciallyavailable liquid products certified by OMRI(Organic Materials Review Institute, Eugene,OR) as a source of N (Table 2). The blendconsisted of PuraVida Grow (644), PuraVida

Bloom (266), and Thrive-Alive (111),all plant-based products from Technaflora

Table 1. Chemical characteristics of the composts used in the experiments.

Characteristicz Units Yard waste Swine Mushroom

Electrical conductivity (mScm1) 2.78 13.4 2.92pH 7.6 5.7 7.36Nitrogen Percent total 1.97 2.38 2.31Phosphorus Percent total 0.26 1.09 0.93Total carbon Percent total 18.3 31.1 29.4C/N 9:1 13:1 14:1Potassium Percent total 0.97 3.27 1.4Calcium Percent total 1.73 1.3 11.02Magnesium Percent total 0.41 0.48 0.53Sodium Percent total 0.05 0.84 0.24

Ammonium ppm 362 268 679Iron ppm 9,756 624 1,204Zinc ppm 148 372 191Copper ppm 51 43 139Molybdenum ppm


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Plant Products Ltd. (Port Coquitlam, BC,Canada). These three products were addedin a ratio of 3.0:0.35:0.50 (Grow:Bloom:Thrive Alive) to supply organic N at concen-trations similar to that of the inorganic N(target NO3 plus NH4 of 190 mgL

1) in thestandard hydroponic feed. Note that organicfeed A did not include a N and P source; thisallowed us to determine how long the com-

posts would supply N and P to the plantbefore becoming depleted while providing

most other essential nutrients. Leaching ofnutrients from the pots was minimized byallowing only minimal overdrain and bycollecting the excess using saucers for thefirst 46 d of the experiment. Plants receivingorganic feed B initially received organic feedA until the early stages of N deficiencies wereevident based on visual observation (26 Mar.2008), at which time they were switched.Using this approach, the plants would relyon composts as a source of N for as long as

possible before it became necessary to sup-plement with liquid sources of N. Proprietaryliquid organic fertilizers are relatively expen-sive and will potentially plug drippers so it is

practical to delay their use. There were a totalof seven treatments (Table 3). The pH of alltreatments was adjusted to 6.5 with citricacid. The experiment was laid out in arandomized complete block design with fiveexperimental units (plants) of each treatmentin each of two blocks (total of 70 plants).

Fruit harvest started on 1 May and con-tinued to 1 June, at which time the experi-ment was ended (total of three mature trusses

plus all remaining immature fruit). Fruit fromeach plant were weighed at harvest andgraded individually to maxi-extra large, extralarge, large, medium, and small (> 8.9 > 7.0 >6.4 > 5.7 > 5.1 cm in diameter, respectively).

Unmarketable fruit equal to or less than 5.1cm in diameter or with obvious blemishes,cuticle cracking, splitting, blossom-end rot,or irregular shape were treated as culls.

Expt. 2. Seeds of the cluster cultivarIdool(Seminis Seeds, Saint Louis, MO) were sownon 29 Apr. and transplanted to the experi-mental greenhouse compartment on 10 June.Three substrates were used, all with a base of

peat/perlite: 1) peat/perlite (control); 2) 50%YW compost (described in Expt. 1); and 3)50% mushroom (Mush) compost. All mixeswere blended on a volume/volume basis.Mushroom compost was obtained from AllSeasons Mushrooms (Abbotsford, BC, Can-ada). The raw material was composed of 58%wheat straw (0.35% N on a dry weight basisand 12% moisture), 38% dry poultry waste(3.6% N on a dry weight basis and 25%moisture), and 4% gypsum (10% moisture).The mineral analysis of the spent mushroomcompost is detailed in Table 1. In addition,three liquid feeds were tested: standardhydroponic feed (control), organic feed Boriginally used in Expt. 1 but now at twoconcentrations (the low concentration ofapplication used the same ratio of Grow,Bloom, and Thrive Alive as that of Expt. 1and the high concentration used a ratio of4.55:4.50:0.50 of Grow, Bloom, and Thrive

Alive, respectively), and a fish-based organicfeed (organic feed C), also at two concen-trations (Table 2). The fish product wasOMRI-certified Pacific Natural (230.3)from Great Pacific BioProducts Ltd. (Delta,BC, Canada). All liquid fertilizer treatments

began on the day of transplanting. The treat-ments for Expt. 2 are summarized in Table 4.A randomized complete block design withtwo blocks was used with seven experimentalunits (plants) of each treatment per block

(total of 126 plants).Fruit harvest was from 7 Aug. to22 Oct. at

which time the experiment was ended (totalof nine mature trusses plus all remainingimmature fruit). Because a cluster varietywas used, fruit were weighed by truss ratherthan individually. A cluster was harvestedwhen half the fruit had reached breaker stage.Cluster weight and fruit number wererecorded. Culls (unmarketable fruit with

blossom end rot, severe cuticle cracking, ornonuniform shape) were then removed andtheir weight and number recorded. Finally,Grade 2 fruit (still marketable fruit with skin

blemishes, scars, or small cracks) were then

removed and weighed.Postharvest analysis of fruit quality wasconducted only in Expt. 2. Fruit were ob-tained from two harvests, on 19 Sept. and on5 Oct. 2008. At each harvest, 10 fruit of eachtreatment were randomly selected for post-harvest quality evaluation. Fruit were storedfor 3 weeks in a cooler with an air tempera-ture of 10 C (with fluctuation of 0.5 C) andrelative humidity of %80%. Each fruit wasvisually evaluated individually on the day of

harvest and three times a week thereafter.Scores of decay index were: 0 = no sign ofdecay, still firm; 1 = first sign of decay onfruit surface or stem, still firm; 2 = decay onless than 10% of fruit surface with no lesions,still firm enough to market; 3 = first lesion ortoo soft to be considered marketable, end ofshelf life; 4 = multiple lesions or severedesiccation and soft; and 5 = severe decaywith fluid leakage and/or very soft withsevere desiccation, not consumable. Only

the decay index at the end of 21 d is reportedhere. The data of the two harvests werecombined.

Fusarium crown and root rot, caused byFusarium oxysporum f.sp. radicis-lycopersici,was found in some treatments in the secondexperiment. On two sample dates, 15 Sept.and 4 Nov., plants were scored as beingdiseased on the basis of visible symptomsof crown rot and wilting.

Physical analysis. Substrate sampling forbulk density and waterholding capacity wasconducted in the second experiment on 25Oct. 2008. Undisturbed substrate core sam-

ples were collected with an edge-sharpened

cylinder (4.8 cm internal diameter, 2 cmheight; 36.2-cm3 volume) %10 cm from thetop of each pot. Media above and below thecore was carefully removed with a knife.There were 14 samples per treatment.Samples were oven-dried for 2 d at 60 Cand bulk density of the substrate was calcu-lated. The oven-dried cores were then rewet-ted with 50 mL water, allowed to absorbwater for 1 h, and the extra water was thenremoved. An additional 10 mL of water was

Table 3. Compost and liquid feed treatments in Expt. 1.

Treatment abbreviation Substrate Liquid feed

Control 80% peatmoss, 20% perlite Hydroponic20YW-FeedA 20% yard waste compostz Organic feed Ax

20YW-FeedB 20% yard waste compostz Organic feed Bw

20Sw20YW-FeedA 20% swine compost, 20% yard waste composty Organic feed A20Sw20YW-FeedB 20% swine compost, 20% yard waste composty Organic feed B40YW-FeedA 40% yard waste composty Organic feed A40YW-FeedB 40% yard waste composty Organic feed BzIn 60% peatmoss and 20% perlite.yIn 40% peatmoss and 20% perlite.xFeed consisted of K2SO4, calpril, dolopril.wFeed consisted of K2SO4, calpril, dolopril, Technaflora products.

Table 4. Compost and liquid feed treatments in Expt. 2.

Treatment abbreviation Substrate Liquid feed

Control 80% peatmoss, 20% perlite Hydroponics50YW-Feed C High 50% yard waste compostz Organic feed C Highy

50YW-Feed B High 50% yard waste compostz Organic feed B Highx

50YW-Feed B Low 50% yard waste compostz Organic feed B Loww

50YW-Feed C Low 50% yard waste compostz Organic feed C Lowv

50Mush-Feed C High 50% mushroom compostz Organic feed C High50Mush-Feed B High 50% mushroom compostz Organic feed B High50Mush-Feed B Low 50% mushroom compostz Organic feed B Low50Mush-Feed C Low 50% mushroom compostz Organic feed C LowzIn 30% peatmoss and 20% perlite.yFeed consisted of K2SO4, calpril, dolopril, and Pacific Natural products (fish-based organic) at highconcentration.xFeed consisted of K2SO4, calpril, dolopril, and Technaflora products at high concentration.wFeed consisted of K2SO4, calpril, dolopril, and Pacific Natural products (fish-based organic) at lowconcentration.vFeed consisted of K2SO4, calpril, dolopril, and Technaflora products at low concentration.



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added to the sample to ensure completesaturation; the excess was then removed witha syringe. The waterholding capacity foreach sample was calculated as (weight ofsaturated sample weight of dry sample)/volume of the core.

Mineral analysis. For the first experiment,three recently expanded leaves from the topof each plant were collected on 26 Mar. with10 plants per treatment. All leaflets pertreatment were pooled together, dried, and

ground to 20 mesh. On 20 Oct. 2008, threefully expanded leaves from the top of each

plant were collected for the second experi-ment. After drying and grinding to 20 mesh,samples from each of two plants were ran-domly combined for a total of four samples

per treatment.Substrate sampling was conducted after

the last tomato harvest in Expt. 2 on 28 Oct.2008. Samples of %1 kg of substrate weretaken from eight randomly selected pots ineach treatment and combined in pairs for atotal of four samples. Samples were oven-dried for 3 d at 60 C. The leaf and substratesamples were submitted to A & L Canada

Laboratories Inc. (Winnipeg, MB, Canada)for mineral analysis. Leaf minerals weredetermined by inductively coupled plasmaspectroscopy after nitric and hydrochloricacid digestion and substrate minerals, elec-trical conductivity, carbon, C/N, and pH weredetermined by Test Methods for the Exami-nation of Composting and Compost(TMECC, 2009) protocols.

Substrate biological analyses. Substratebiological analyses were conducted in bothexperiments. At each sample date, substratefrom two randomly selected pots per treat-ment, with two cores (2.5 cm diameter 15cm deep) from each pot, were mixed together

as one replicate. In the first experiment,samples were collected in the middle of theexperiment on 21, 22, and 25 Apr. (total ofthree replicates, each taken on a differentday) and just before ending the crop on 27May (five replicates, all taken on the sameday). In Expt. 2, samples were collected

before transplanting (10 June), in the middleof the experiment (5 Aug.), and near the end

of the crop (23 Sept.). Samples were stored at4 C until used.

Fluorescein diacetate analysis hydrolysiswas used as a measure of total microbialactivity because it is simple, rapid, andsensitive (Schnurer and Rosswall, 1982).FDA activity has also frequently been corre-lated with compost-related suppression of

plant diseases (Hoitink and Boehm, 1999).The method was adapted from Green et al.,2006. The samples were first sieved to pass

through a 5-mm mesh. One gram (freshweight) of substrate was placed in a 125-mL Erlenmeyer flask and 50 mL of 60 mMsodium phosphate buffer (pH 7.6) was added.Stock solution (0.5 mL of 4.9 mM FDA) wasadded to start the reaction. Blanks preparedeither without the addition of the FDAsolution or without sample were measuredalong with a suitable number of samplereplicates. The flasks were then placed in anoven at 37 C for 3 h. Once removed from theoven, 2 mL of acetone was added immedi-ately to end the reaction. The flasks wereshaken thoroughly by hand. The contents ofthe flasks were then transferred to 50-mL

centrifuge tubes and centrifuged at 1725 rpmfor 6 min. The supernatant from each samplewas then filtered (Whatman No.2 filter paper)into tubes and the filtrates measured at 490nm on a spectrophotometer (Ultrospec 1100Pro, ultraviolet/visible spectrophotometer;Biochrom, Cambridge, U.K.).

Substrate samples for nematode analyseswere the same as those used for the FDAanalyses. Nematodes were extracted from 60-mL substrate subsamples using Baermann

pans (16 cm diameter, 7-d incubation) (Forgeand Kimpinski, 2007). The nematodes wereheat-killed (70 C for 1 min) and preservedin 4% formalin. Subsequently, 5-mL aliquots

of appropriate dilutions of the nematodesuspensions were poured onto a griddedcounting dish on an inverted microscopeand total nematodes were counted at 40magnification.

The community-level physiological pro-file (diversity) of the bacterial communitywas assessed on substrate samples (the sameas those for FDA and nematodes) from the

second experiment only. EcoLog plates(BioLog Inc., Hayward, CA) were seededwith 0.15 mL of 1:1000 and 1:10,000 dilu-tions (in phosphate buffer) of substrate sub-samples. An automatic plate reader was usedto assess color development at 1, 2, 3, 4, 5,and 7 d after inoculation of the plates. Colorintensity was averaged over the three repli-cates for each substrate in each plate. Thetime integral of absorbance readings wasapproximated using a difference equation.

The number of substrates used by Day 7was used as an indicator of the diversity ofcatabolic capacities in the bacterial commu-nity. The time integral of average absorbance

per positive substrate and the number ofsubstrates used were the parameters that wereanalyzed statistically.

Statistical analysis. The data were ana-lyzed using the General Linear Model (GLM)of SAS (SAS Institute, Cary, NC). Duncansmultiple range tests were used for meansseparation among treatments, and orthogonalcontrasts were used to evaluate groupings oftreatments. Relationships between biologicalfactors were analyzed using the Regression

(REG) procedure of SAS.

Results

Expt. 1. In the first experiment, treatmentshad significant effects on yield (Table 5). Theconventional hydroponic treatment resultedin significantly higher yield (marketable andtotal) than any of the organic treatments. Theorganic treatment showing yield closest tothe hydroponic control was 40Van-FeedBat 82% of the control. Within the organictreatments, yields (marketable and total) indescending order were 40Van-FeedB = 20Van-FeedB > 20Sw20Van-FeedB = 20Sw20Van-

FeedA > 40Van-FeedA = 20Van-FeedA. Theorganic treatment showing the lowest yieldwas 18% of that of the hydroponic control.Organic feed B generally resulted in signif-icantly higher yield (marketable, unmarket-able, and total)thandid Feed A, which had no

N or P.The mineral content of leaf tissue could

not be statistically evaluated because all

Table 5. Treatment effects on yield, microbivorous nematodes, and FDA analysis in Expt. 1.

Treatment

Yield (kg/plant) Nematodes (per 60 mL) FDA (mgkg1 soil/3 h)

Marketable Unmarketable Total 21 Apr. 27 May 21 Apr. 27 May

Control 5.59 az 0.21 b 5.80 a 1,364 d y 2,086 c 2.16 2.38 cd

20YW-FeedA 0.97 d 0.07 c 1.03 d 2,992 c 2,922 bc 2.24 2.15 d 20YW-FeedB 4.14 b 0.26 b 4.40 b 5,104 bc 4,189 abc 2.53 3.37 b20Sw20YW-FeedA 2.31 c 0.23 b 2.54 c 8,653 ab 4,391 ab 2.98 2.45 cd 20Sw20YW-FeedB 2.46 c 0.53 a 2.99 c 12,540 a 6,987 ab 2.99 3.76 ab40YW-FeedA 1.44 d 0.05 c 1.49 d 4,723 c 6,670 a 2.47 3.11 bc40YW-FeedB 4.49 b 0.25 b 4.74 b 6,336 bc 5,949 ab 2.73 4.18 aSignificance of selected a priori contrasts of treatment effects:Control versus organic *** NS *** *** ** NS **Feed A versus Feed B *** *** *** NS NS NS ***20YW versus 20YW20Sw NS *** NS *** NS NS NS20YW versus 40YW NS NS NS NS * NS **20YW20Sw versus 40YW ** *** NS *** NS NS *zNematode counts are presented, but data were log10 transformed for statistical analysis.yMeans within each column that are followed by different letters are significantly different (P < 0.05) according to Duncans multiple range test.

NS, *, **, ***Nonsignificant or significant at P # 0.05, P # 0.01, orP # 0.001, respectively.FDA = fluorescein diacetate analysis.

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samples for each treatment were pooledbefore analysis, but some broad generaliza-tions could be observed. Nitrogen wassimilarin the hydroponic control treatment and inthose with swine compost (5.94% and 5.52% 0.01, respectively; mean SD) but lower inall other treatments (2.42% 0.40). Potas-sium was highest in treatments with swinecompost (5.05% 0.05) and somewhatlower in all other treatments (3.37% 0.54). Iron was higher in the control treat-

ment (164 ppm) than in the organic treat-ments (96 ppm 18). Other elements weresimilar in all treatments.

The effect of treatments on nematodepopulations in Expt. 1 is shown in Table 5.Only bacterial-feeding and fungal-feedingnematodes were observed in the samples. Inthe first sample (21 Apr.), 20Sw20YW-FeedB had significantly more nematodes thanany other treatment except 20Sw20YW-FeedA. None of the other organic treat-ments differed from each other. Substratewith 20Sw20YW had higher nematode pop-ulations than did substrate with 20YW or40YW. In the second sampling (27 May), the

40YW-Feed A treatment had significantlymore nematodes than 20YW-Feed A and thehydroponic control. None of the other organictreatments differed from each other. Contrastanalysis showed that, collectively, the 40YWtreatments had higher nematode populationsthan did the 20YW treatments. On bothsampling dates, organic treatments had sig-nificantly higher nematode counts than thehydroponic control, but organic feed A andorganic feed B treatments did not differ.

There were no significant differences inFDA measurements among the seven treat-ments in the first sampling of Expt. 1 (Table5). However, in the second sampling, feed B

organic treatments were significantly higherthan the control, and the 40YW-Feed Btreatment was significantly higher than mostother treatments. From the contrast analyses,the hydroponic control showed lower FDAvalues than the organic treatments, andorganic feed A was less than organic feedB. In addition, the 40YW treatments showedsignificantly higher FDA values than the20YW treatments, and the 40YW treatmentswere greater than the 20YW20Sw treatments.

Expt. 2. In the second experiment, treat-ments had significant effects on yield (Table6). Organic treatments 50Mush-Feed B Lowand 50YW-Feed B Low resulted in compa-rable yield (marketable and total) to thehydroponic control. Within the organic treat-ments, yields (total) in descending orderwere 50Mush-Feed B Low = 50YW-Feed BLow> 50Mush-Feed C Low = 50YW-Feed CLow > 50YW-Feed B High = 50Mush-FeedB High = 50YW-Feed C High = 50Mush-Feed C High. Note that 50YW-Feed B Highwas greater than 50YW-Feed C High and50Mush-Feed C High and that 50Mush-FeedB High was greater than 50Mush-Feed CHigh. From the contrast analyses, the controltreatment was generally significantly higherthan the organic treatments. Low concentra-tions of organic feed resulted in significantly

higher yield (marketable, unmarketable, andtotal) compared with higher concentrationsof organic feed. Organic feed B generallyresulted in significantly higher yield (market-able and total) than did Feed C. There was nosignificant difference in yield (marketableand total) resulting from the different com-

posts. However, YW compost produced moreunmarketable fruit than did the mushroomcompost.

The analysis of postharvest data are

shown in Table 6. Overall, the hydroponiccontrol was inferior in postharvest quality tothe eight organic treatments, having a highdecay index of 4.7 (P = 0.003). In order ofdecreasing postharvest quality, treatmentscould be arranged as 50YW-Feed B High,50Mush-Feed C High, 50Mush-Feed B High,50YW-Feed C High, 50YW-Feed B Low,50YW-Feed C Low, 50Mush-Feed C Low,50Mush-FeedB Low, and control. Generally,contrast analysis showed no difference

between the two types of liquid organicfertilizer. Yard waste compost was superior(low decay index) to mushroom compost andthe high concentration of liquid organic

fertilizer was superior (low decay index) tothe low concentration. There was a positiverelationship between yield and postharvestdecay (y = 7.8 + 3.3x, R2 = 0.72, P = 0.004;data taken from treatment means).

Substrates in Expt. 2 sampled beforetransplanting showed significant differencesin nematode counts (Table 7). As for Expt. 1,only bacterial-feeding and fungal-feedingnematodes were observed. The lowest countswere found in the hydroponic control and thehighest in the mushroom compost. The effect

of treatments on nematode populations inExpt. 2 is shown in Table 8. In the sampletaken on 5 Aug., 50YW-Feed C High hadsignificantly more nematodes than 50YW-Feed C Low and more nematodes than anyother treatment, including the control. Exceptfor these two treatments, most of the organictreatments did not differ from each other.From contrast analyses, organic feed treat-ments had significantly higher nematodecounts than the control. Organic feed C

treatments showed higher nematode countsthan did the organic feed B treatments. Therewas no significant difference in nematodecounts between high and low organic feedconcentrations. Yard waste compost showeda significantly higher nematode count thandid the mushroom compost.

In the nematode sample taken on 23 Sept.,50YW-Feed C High and Low and 50Mush-Feed C High and Low treatments had sig-nificantly more nematodes than any othertreatment, including the control. Results ofcontrasts were the same as found for the 5Aug. samples.

In terms of pretreatment FDA values for

Expt. 2, there were no differences betweenthe control and the YW compost, but themush compost had higher values (Table 7).After treatments were applied, there weresignificant differences in FDA measurementsamong the nine treatments in the Augustsampling of Expt. 2 (Table 8). The 50YW-FeedC Low, 50YW-FeedC High, 50Mush-FeedB High, and 50Mush-Feed C Hightreatments showed significantly higher FDAactivity than the control. None of the otherorganic treatments differed from the control

Table 6. Treatment effects on yield and postharvest decay in Expt. 2.

Treatment

Yield (kg/plant)

Decay index after 21 dMarketable Unmarketable Total

Control 8.21 az 0.28 def 8.49 a 4.7 ab50YW-Feed C High 2.68 cd 0.67 b 3.35 de 3.6 cde50YW-Feed B High 3.24 c 1.09 a 4.34 c 3.0 e50YW-Feed B Low 7.82 a 0.46 bcd 8.28 a 3.9 cd 50YW-Feed C Low 6.18 b 0.59 bc 6.77 b 4.1 bc50Mush-Feed C High 2.25 d 0.40 cde 2.65 e 3.4 de50Mush-Feed B High 3.37 c 0.20 ef 3.57 cd 3.6 cde50Mush-Feed B Low 8.42 a 0.10 f 8.52 a 4.8 a50Mush-Feed C Low 6.64 b 0.35 cdef 6.99 b 4.7 abSignificance of selected contrasts of treatment effects:Control versus organic *** * *** *High versus low *** *** *** *Feed B versus C *** NS *** NSYW versus mush NS *** NS *zMeans within each column that are followed by different letters are significantly different (P < 0.05)according to Duncans multiple range test.

NS, *, **, ***Nonsignificant or significant at P # 0.05, P # 0.01, orP # 0.001, respectively.

Table 7. Initial microbivorous nematode counts and FDA values in each substrate in Expt. 2.

Substrate Nematodes (per 60 mL substrate) FDA (mgkg1 soil/3 h)

Control 2,710 cz,y 2.51 b50YW 4,576 b 2.95 b50Mush 9,900 a 8.08 azMeans within each column that are followed by different letters are significantly different (P < 0.05)according to Duncans multiple range test.yNematode counts are presented, but data were log10 transformed for statistical analysis.FDA = fluorescein diacetate analysis.



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or from each other. Contrast analysis showedthat organic feeds had higher overall FDA

values than did the hydroponic control. Incomparing feed types, organic feed C hadsignificantly higher FDA values than didorganic feed B.

There were also significant differences inFDA measurements in the September sam-

pling (Table 8). The 50Mush-Feed C High,50YW-Feed C High, and 50Mush-Feed CLow treatments showed significantly higherFDA values than the control. None of theother organic treatments differed from thecontrol or from each other. Overall, contrastanalysis showed that organic feeds had higherFDA values than did the hydroponic control.In comparing feed types, organic feed C hadsignificantly higher FDA values than did or-ganic feed B. The higher concentrations of or-ganic feeds had higher FDA values than didlow concentrations.Mushroomcompost showedsignificantly higher FDA values than did theyard waste compost.

Analyses of the community-level physio-logical profile of the bacterial communitythrough EcoLog plates in the Septembersampling also revealed significant effects oftreatments (Table 8). The total number ofsubstrates used by the seventh day of incu-

bation was greatest for the 50Mush-Feed BLow treatment, but it did not differ signifi-cantly from the control, which was interme-

diate to the various organic treatmentcombinations. Bacterial communities in the

50Mush-Feed C High treatment and the50YW-Feed B High treatments used signif-icantly fewer substrates than the control. Noother treatments were significantly differentfrom the control. The contrast comparinghigh and low feed concentrations was highlysignificant with mean values of 23.2 and 27.1for the high and low feeds, respectively.

The high concentration of organic feed Cinduced a high incidence of fusarium crownand root rot. On 15 Sept., other than one plantin the low concentration of organic feed B,

plants receiving high organic feed C concen-trations were the only ones to show symp-toms of fusarium infection with 39% of the

plants showing symptoms. By 4 Nov. (Table8), 61% of all plants receiving the highconcentration of organic feed C (both com-

post treatments combined) had symptoms offusarium crown rot, and 18% of all plantsreceiving the high concentration of organicfeed B had symptoms of fusarium crown rot.In all, 24 plants out of 126 (19%) developedsymptoms of fusarium crown and root rot.

The bulk density and waterholding capac-ity of the substrates in Expt. 2 are shown inTable 8. Substrate bulk density was signifi-cantlyhigher in theorganic treatments than inthe hydroponic control, which was the lowestat 0.119 gcm3. From contrast analyses, yard

waste compost had significantly higher bulkdensity than did mushroom compost. Organicfeed C resulted in higher bulk density than

that of organic feed B. The waterholdingcapacity of the hydroponic control was0.730 gcm3, which was significantly higherthan the organic treatments. Yard wastecompost had a higher waterholding capacitythan did the mushroom compost. However,

bulk density and waterholding capacity didnot differ between high and low concentra-tions of the organic feeds.

For both experiments, substrate biologicalvariables were regressed against each otherand against yield. The hydroponic controlwas excluded from the analysis in bothexperiments as were the high organic feedtreatments in the second experiment as a

result of the occurrence of fusarium crownand root rot, which could confound anyrelationships with yield. A summary of sig-nificant regressions is presented in Table 9. Inthe first experiment (second sample date),FDA values were positively related to yield,

but in the second experiment, FDA valueswere negatively related to yield as werenematode populations. Nematode popula-tions were significantly correlated withFDA activity in Expt. 2.

Substrate mineral content measured at theend of the experiment is presented in Table10. To summarize, contrast analysis showedthat the eight organic treatments were signif-icantly different from the hydroponic treat-ment in having higher N, sulfur (S), P, K, Ca,

boron (B), zinc (Zn), manganese (Mn), iron(Fe), and copper (Cu). Substrate electricalconductivity (EC) and saturated pH valueswere also higher in the organic treatmentsthan in the hydroponic control. This wascorroborated by measurements of leachateEC and pH collected on four occasionsduring the experiment (data not presented;leachate pH values were generally higher thanthe saturated pH values in all treatments). Thehigh feed concentrations tended to have thegreatest substrate EC values; the exceptionwas 50Mush-Feed C High, which had an EC

Table 8. Treatment effects on substrate physical and microbiological characteristics in Expt. 2.

Treatment

Bulkdensity

(gcm3)

Waterholdingcapacity(gcm3)

Microbivorous nematodes(per 60 mL) FDA (mgkg1 soil/3 h)

EcoLogsubstrates

usedFusarium

(%)5 Aug. 23 Sept. 5 Aug. 23 Sept.

Control 0.119 cz 0.730 a 678 ey 590 d 2.08 d 1.64 d 26.6 ab 050YW-Feed C High 0.227 a 0.596 bc 42,742 a 24,728 a 3.46 ab 3.11 ab 27.2 ab 3650YW-Feed B High 0.223 a 0.610 b 1,910 cd 1,883 c 2.38 cd 1.97 d 17.6 d 1450YW-Feed B Low 0.213 a 0.610 b 1,426 d 3,247 c 2.51 bcd 1.81 d 25.6 bc 750YW-Feed C Low 0.226 a 0.589 bcd 10,930 b 21,560 ab 3.80 a 2.31 cd 28.2 ab 050Mush-Feed C High 0.162 b 0.557 d 1,751 cd 11,792 b 3.21 abc 3.82 a 23.0 c 2550Mush-Feed B High 0.149 b 0.620 b 1,021 de 1,390 c 3.30 abc 2.29 cd 25.0 bc 450Mush-Feed B Low 0.149 b 0.564 cd 1,566 cd 1,408 c 2.79 abcd 1.86 d 29.4 a 0

50Mush-Feed C Low 0.155 b 0.593 bcd 2,684 c 19,228 ab 3.10 abcd 2.91 bc 25.2 bc 0Significance of selected a priori contrasts of treatment effects:Control versus organic *** *** *** *** ** ** NSHigh versus low NS NS NS NS NS ** ***Feed B versus C * NS *** *** ** *** NSYW versus mush *** * *** ** NS * NSzMeans within each column that are followed by different letters are significantly different (P < 0.05) according to Duncans multiple range test.yNematode counts are presented, but data were log10 transformed for statistical analysis.

NS, *, **, ***Nonsignificant or significant at P # 0.05, P # 0.01, orP # 0.001, respectively.FDA = fluorescein diacetate analysis.

Table 9. Selected significant relationships among microbial and yield measurements in Expts. 1 and 2.

Relationshipz Analysisy Equation R2 P

FDA and nematodesx Expt. 2, sample 1 y = 1.47 + 1.32x 0.30 0.01

Expt. 2, sample 2 y = 0.75 + 0.79x 0.38 0.004Yield and FDA Expt. 1, sample 2 y = 0.46 + 1.95x 0.36 0.0005

Expt. 2, sample 2 y = 16.34 1.5x 0.42 0.002Yield and nematodesx Expt. 2, sample 1 y = 28.62 3.89x 0.44 0.001

Expt. 2, sample 2 y = 22.54 2.54x 0.73


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value similar to the low-feed concentrations.-Percent organic matter and substrate C/N ratiowere lower in the organic treatments than in thehydroponic control. The low feed concentrationhadsignificantly lower N, P, K, andB andhigherMn than the high-feed treatments; the C/N ratioand pH were higher but the EC was lower. FeedB showed lower P but higher B,Zn,Mn, and Cuthan did feed C, and its pH was also higher. Interms of the two composts, YW compost hadlower N,S, P, Ca, B,Zn,Mn, and Cuand higher

Fe. Percent carbon, organic matter, C/N, and pHwere also lower in the YW compost.

In terms of foliarmineral content, contrastanalysis showed that the only elements thatwere significantly different between the con-trol and the organic treatments were S, P, Ca,B, Mn, and Cu (Table 11). The leaf tissuecontent of S, P, Mg, Ca, B, Mn, and Cu weresignificantly higher in the leaves from thefeed B treatments than in those from feed C;only the Fe content was significantly higherin the leaves from the feed C treatments. Thehigh concentration of organic feed resulted inhigher S, P, Mg, B, Mn, and Fe and less Ca inleaves than did the low concentration. Mush-

room compost resulted in significantly higherfoliar Ca and Cu but less B, Mn, and Fe thandid the YW compost.

Discussion

Studies comparing yield of organicallyand conventionally grown crops often giveinconsistent results. Some studies have foundyield to be lower in organic than in conven-tional treatments in both field andgreenhousecrops (Heeb et al., 2005, 2006; Mader et al.,2002). On the other hand, no significantdifferences in total marketable yield of sweet

pepper (del Amor, 2007) and tomato (Rippy

et al., 2004) have been observed whencomparing organic and mineral fertilization,although in the study with tomato, the harvestduration was relatively short. Herencia et al.(2007) also found that crop yield was notstatistically different between organic andmineral fertilizer treatments. In our firstexperiment, the hydroponic control had ahigher yield than any of the organic treat-ments. The highest-yielding organic treat-ment (40YW-FeedB) in the first experimenthad a total yield that was 82% of thehydroponic control. However, in the secondexperiment, the combination of 50% com-

post with a low concentration of organic feedresulted in yield ranging from 80% to 100%that of the hydroponic control. The relativelyhigher organic yield in the second experi-ment may have been associated with thehigher concentrations of composts used aswell as the fact that liquid feed treatmentsstarted at transplanting rather than 1 monthlater, like in Expt. 1. In the second experi-ment, organic feed B produced significantlyhigher yield than did organic feed C. Thereason for this is unknown; the two feedsoriginated from different sources (plant ver-sus fish) andalthoughmineral composition ofthe two was as similar as we could manage,there were inevitably some differences bothT

able10.MineralcontentofsubstratesusedinExpt.2.

Treatment

Nitrogen

(%)

Sulfu

r

(ppm

)

Phosphorus

(%)

Potassium

(%)

Magnesium

(%)

Calcium

(%)

Sodium

(%)

Boron

(ppm)

Zinc

(ppm)

Manganes

e

(ppm)

Iron

(ppm)

Copper

(ppm)

Carbon

(%)

Organic

matter(%)

C/N

Electrical

conductivity

(mS

cm1)

pH

saturated

Control

1.11ez

3,347

b

0.07f

0.34d

0.16

1.34c

0.05

7.56d

15c

51e

1,864c

10e

44.47a

80.0a

41.5a

1.34c

4.43f

50YW-FeedCHigh

2.10a

3,975

b

0.87cd

0.55abc

0.27

2.04c

0.08

7.40d

124b

187d

8,706b

47de

30.49d

54.9d

14.5d

3.43a

4.93de

50YW-FeedBHigh

1.81cd

3,190

b

0.38ef

0.61a

0.42

1.43c

0.07

39.75b

225a

360b

9,710a

162b

26.84e

48.3e

15.0d

3.14b

5.13cd

50YW-FeedBLow

1.77d

3,550

b

0.26f

0.41cd

0.32

1.66c

0.06

24.34c

215a

387b

8,847b

153b

30.93d

55.7d

17.5bc

2.39a

5.20c

50YW-FeedCLow

1.68d

3,716

b

0.63de

0.44bcd

0.28

1.97c

0.08

10.81cd

109b

183d

9,189ab

39de

30.42d

54.8d

18.0bc

2.27b

4.85e

50Mush-FeedCHigh

2.12a

6,677

a

2.86a

0.61a

0.62

6.18a

0.76

12.30cd

147b

248c

1,947c

86cd

35.57bc

64.0bc

16.8c

2.30b

5.56b

50Mush-FeedBHigh

1.96abc

6,915

a

1.03c

0.57ab

0.29

6.15a

0.09

73.65a

249a

392b

2,261c

223a

35.49bc

63.9bc

18.0bc

3.40a

6.25a

50Mush-FeedBLow

2.01ab

6,559

a

0.69cde

0.42cd

0.25

5.54a

0.08

52.68b

263a

454a

2,406c

228a

37.23b

67.0b

18.8b

2.57b

6.38a

50Mush-FeedCLow

1.93bc

7,577

a

1.73b

0.43cd

0.21

4.12b

0.12

14.59cd

145b

275c

2,061c

111bc

33.37c

60.1c

17.0bc

2.57b

6.18a

Significanceofselectedcontrastsoftreatmenteffects:

Controlversusorganic

***

***

***

**

NS

***

NS

***

***

***

***

***

***

***

***

***

***

Highversuslow

***

NS

***

***

NS

NS

NS

*

NS

*

NS

NS

NS

NS

***

***

*

FeedBversusC

NS

NS

***

NS

NS

NS

NS

***

***

***

NS

***

NS

NS

NS

NS

***

Yardwasteversusmush

***

***

***

NS

NS

***

NS

***

*

***

***

***

***

***

**

NS

***

zMeanswithineachcolumnthatarefollowedbydifferentlettersaresignificantlydifferent(P mushroom > YW.Organic treatments also showed reducedwaterholding capacity compared with thehydroponic treatment. However, the frequentirrigation schedule that we used, typical ofcommercial greenhouses, would likely min-imize any influence of changes in substratewaterholding capacity. The EC of the com-

posts could also be a factor. In the first

experiment, the high EC of the swine com-post (likely the result of high K and sodium),even when mixed at the relatively low con-centration of 20%, may have influenced the

plants, which showed curling in the upperleaves possibly as a result of salinity stress. Inthe second experiment, the EC of the sub-strates measured before, during, and after theexperiment was not excessive. Nevertheless,higher EC may have contributed marginallyto the lower yields of the organic comparedwith the hydroponic treatment and to thelower yields of the high compared with thelow feed concentrations, perhaps by predis-

posing the plants to fusarium crown and root

rot (Dorais et al., 2001; Triky-Dotan et al.,2005). The relationships among substrate-solution EC, fusarium, and yields in thecontext of organic production practicesdeserves additional study.

Although the fish-based feed (feed C)contributed substantially more P to the sub-strate than did the plant-based feed (feed B)over time, the effects on plant P status (asmeasuredin leaves) were notas great andlikelynot to affect yields. However, high P values inthe substrate could perhaps limit Ca availabilitythrough precipitation reactions. The sustain-ability of long-term (yearly) additions of high-P feeds could not be determined in this study.Boron and Mn were two of the more variablemineral elements in both substrate and leaftissue, but no symptoms of deficiency ortoxicity were observed in any of the treatments.

Conclusions

Compost derived from either YW or swinemanure, along with supplemental organic Ca,K, Mg, and SO4, in a peat-based organic mixwas insufficient to maintain a greenhousetomato crop for more than 1 month withoutshowing visible tissue nutrient deficienciesand reduced yield. A supplemental fish-basedor plant-based liquid feed containing N and P

was necessary for adequate growth of a long-term crop. The best organic combination formaximum yield was 50% compost from eitherYW or mushroom substrate in combinationwith a low concentration of liquid feedderivedfrom plant sources. Those yields were as highas those obtained from a conventional hydro-

ponic regimen. In terms of postharvest fruitquality, the decay index was generally lowerin the organic treatments than in the hydro-

ponic control. Interestingly, a higher concen-

tration of either fish-based or plant-basedliquid organic feed caused proliferation offusarium crown and root rot, which severelyreduced yield. The high incidence of fusariumcrown and root rot was not related to physicalcharacteristics of the substrate. The microbio-logical activity measured as FDA, EcoLogvalues, and nematode counts were signifi-cantly higher in the organic treatments thanin the hydroponic treatment, and nematodeabundance was often positively correlatedwith FDA activity.

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800-organic fertilizer for greenhouse tomatoes

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