As opposed to other popular so- Indoor Gardening with Hydroponics: A cial media platforms like Facebook Reddit Community Analysis to Identify (Facebook, Menlo Park, CA), Twitter (Twitter, San Francisco, CA), or Insta- Knowledge Gaps gram (Facebook), Reddit’s structure, centered on user-generated, anony- mous discussions, make it particularly 1 2 1 Elisa Solis-Toapanta , Andrei Kirilenko , and Celina Gomez suitable for searching knowledge from like-minded participants. With a cur-
ADDITIONAL INDEX WORDS. content analysis, data mining, online communities, rent average of 330 million monthly social media, urban agriculture active users, Reddit is the sixth most visited website in the world (Statista, SUMMARY. Social media platforms such as Reddit, centered on user-generated, 2019). Over half of its users are based anonymous discussions, can facilitate the exchange of information and resources in the United States, making it the across niche online communities known as ‘‘subreddits.’’ Using data mining tools and content analysis methods, our objectives were to identify recurring questions fourth most popular website at the and characterize comment (‘‘response’’) accuracy from four subreddits focused on national level (Alexa, 2019). In 2016, hydroponic indoor gardening (r/hydro, r/Hydroponics, r/UrbanFarming, and the Reddit user base for the United r/Aerogarden). A total of 1617 original posts (OPs) were classified into one of ten States was distributed as follows: 22% topics and 4891 primary responses were analyzed for accuracy. The three topics between the ages of 18 and 29 years; with the most OPs (production systems, plant lighting, and root-zone environ- 34% between the ages of 30 and 49 ment), which accounted for 50% of the total OPs, were subcategorized and in- years; 25% between the ages of 50 and ductively analyzed. Most posts in the analyzed subreddits related to confusion 64 years; and 19% older than 64 years regarding the design and implementation of appropriate hydroponic production (Statista, 2016). In addition, there is systems. In addition, misinformation about plant lighting is a major part of dis- an almost equal distribution between cussions about growing plants indoors. There are also knowledge gaps regarding nutrient solution management, particularly about fertilizer formulation, pH bal- male and female users (Statista, 2019). ance, and on the impact that solution temperature has on plant growth and de- Because Reddit has a diverse userbase velopment. In general, there were no differences among response accuracy for all who regularly ask and/or answer topics included in our analysis. However, regardless of topic, responses for most questions, it enables the implementa- OPs had less than 50% accuracy, which demonstrates that misinformation can be tion of data mining and content anal- disseminated in social media platforms such as Reddit. As suggested by the results of ysis methods to help uncover common this study, targeted, open access research and outreach efforts offer an opportunity themes within public online discus- to address knowledge gaps among consumers interested in indoor gardening. sions (Chen et al., 2015; Kumar et al., 2018; Lewis et al., 2013; Wu ew media marketing via social blogs, podcasts, and webinars are com- et al., 2014). By unpacking patterns or media provides tremendous monly being used as ubiquitous com- trends used to extract common topics Nopportunities for the green munication tools for public engagement within subreddits, recurring questions industry to engage with customers (Davies and Hara, 2017). In addition, can be identified to help describe (Peterson et al., 2018; Torres et al., discussion forums like Reddit (Reddit, knowledge gaps in specific online 2019). Likewise, agricultural outreach San Francisco, CA) have enabled bi- communities (Agichtein et al., 2008; efforts are increasingly relying on so- directional communication between sci- Nicol, 2018). cial media platforms to reach stake- entists and the general public (Hara Indoor gardening, which typically holders (Bik et al., 2015; Lubell and et al., 2019). The Reddit platform can integrates small-scale edible crop (e.g., McRoberts, 2018; Osterrieder, 2013; facilitate anonymous exchange of com- herbs, greens, and low-profile fruits and vegetables) production with in- Zipper, 2018). Video channels, online ments, images, and other content shar- door farming, has received limited ing that can be used as dynamic and Received for publication 8 Jan. 2020. Accepted for research attention compared with constantly updated learning resources publication 25 Feb. 2020. commercial plant production in con- (Kumar et al., 2018). Users seeking Published online 24 March 2020. trolled environments. Recently ranked 1 information about specific topics based Environmental Horticulture Department, University as one of the fastest-growing garden of Florida, Institute of Food and Agricultural Sciences on personal experiences or common trends in horticulture, indoor garden- (IFAS), 1549 Fifield Hall, Gainesville, FL 32611- interests engage in Reddit online com- 0670 ing is a trending topic among online munities known as ‘‘subreddits,’’ which 2Tourism, Hospitality, and Event Management De- communities, which are significant partment, University of Florida, 240B Florida Gym, are focused discussion forums dedicated drivers for this growing market seg- Gainesville, FL 32611-0670 to specific themes. Nonetheless, despite ment (Garden Media Group, 2019; We thank the U.S. Department of Agriculture Na- active input from online community Thij et al., 2016). As of Nov. 2019, tional Institute of Food and Agriculture, Multistate Research Project NE1835: Resource Optimization in members, expert advice in social media indoor gardening subreddits such Controlled Environment Agriculture, for supporting platforms such as Reddit can be limited as r/UrbanFarming, r/Hydroponics, this research. compared with the amount of amateur- and r/microgrowery, among others C.G. is the corresponding author. E-mail address: generated online content. This draw- cgomezv@ufl.edu. (each with up to 174,000 current sub- back is particularly visible for trending scribers) have numerous users who This is an open access article distributed under the CC BY-NC-ND license (https://creativecommons.org/ topics that have limited research-based actively engage in discussions relevant licenses/by-nc-nd/4.0/). information available to the public to indoor gardening with hydroponic https://doi.org/10.21273/HORTTECH04574-20 (Bessi et al., 2015). systems, which are popular among
346 • June 2020 30(3) hobbyist gardeners (Jones, 2014; (Oracle Corp., Redwood Shores, (<4) and long (>25) symbols; 2) re- Resh, 2015). Public discussions in CA). Data were then filtered to leave moving a list of English stop words Reddit about personal experiences with only relevant OPs and comments (i.e., commonly used words in the indoor plant production are valuable from each subreddit by searching English language such as articles) resources as researchers try to address for the terms ‘‘suggest,’’ ‘‘help,’’ obtained from Ranks NL (Amsterdam, the needs of indoor gardeners. Thus, in ‘‘advice,’’ ‘‘recommend,’’ ‘‘search,’’ The Netherlands); 3) removing stop an effort to identify knowledge gaps ‘‘how to,’’ ‘‘advise,’’ and ‘‘wrong,’’ words from a customized list contain- within online communities, the objec- their inflectional forms, and typical ing words that frequently appeared tives of this study were to: 1) classify misspellings, which were previously within OPs but were either non-topic and quantify recurring questions (i.e., noted as being commonly used in the specific (e.g., help, advice) or unrelated original posts or ‘‘OPs’’) within hydro- selected subreddits. The dataset time- to a particular topic (e.g., water, awe- ponic indoor gardening subreddits; frame ranged from June 2012 to June some, excited); 4) stemming (i.e., re- and 2) characterize the accuracy of 2019, which provided enough data ducing inflected words to their word comments (i.e., responses) given to points for a robust analysis from recent stems); 5) transforming words to low- OPs posted within these subreddits. threads. Data were imported into ercase; 6) transforming words with We hypothesized that most questions Microsoft Excel (Microsoft Corp., misspellings, variant spellings, and syn- would relate to equipment for hydro- Redmond, WA) for processing. onyms to a common term; and 7) ponic production and environmental TOPIC SELECTION. Based on three filtering the most frequent and infre- requirements for indoor gardening. books for hydroponic plant production quent words (e.g., those encountered Furthermore, considering the lack of (Jones, 2005, 2014; Resh, 2015) and in over 70% and less than 1.5% of expert training within the subreddits readily available syllabi from college-level documents, accordingly). Finally, the evaluated, we hypothesized that a large hydroponic courses at the University of main topics appearing in the pre-pro- percentage (>50%) of responses to OPs Florida, Iowa State University, and The cessed reviews were extracted using would provide inaccurate information. Ohio State University, a list of nine Latent Dirichlet Allocation methods To our knowledge, no other horticul- distinctive topics relevant to hydroponic as implemented in the RapidMiner ture-related studies have used data indoor gardening was developed (Table package with optimized topic density/ mining and content analysis methods 2). In addition, a tenth topic identified as word density parameters. to identify knowledge gaps within ac- ‘‘others’’ was included for OPs that After completing the topic mod- tive online communities. could not be easily categorized, typically eling, the discovered topics were containing questions that were not in- manually revised for accuracy and in- Materials and methods cluded in any other topic description, or terpretation. About 20% of all OPs DATA COLLECTION. Following compound questions that pertained to were found to be misclassified be- procedures consistent with published two or more topics. Afterward, a list of cause they either did not belong to approaches to Reddit content analysis specific search words for each topic was a preselected subreddit or belonged (Brett et al., 2019; Chew et al., 2019; created, assuring no overlap among to ‘‘others’’ and were wrongfully clas- Lea et al., 2019; Sharma et al., 2017; topic descriptions. sified into another topic. In addition, Sowles et al., 2018), four subreddits DATA PROCESSING AND CONTENT as the topic revision was completed, were selected to be sampled based on ANALYSIS. All data were processed us- commonly used jargon terms [e.g., relevancy to the objectives of this ing RapidMiner Studio software (ver- nutes = nutrients, res = reservoir, and study, subscriber number, and com- sion 9.1; RapidMiner, Boston, MA) cukes = cucumber (Cucumis sativus)] munity age: r/hydro, r/Hydroponics, following content analysis methods de- were included as topic descriptors. r/Urbanfarming, and r/Aerogarden scribed by Krippendorff (2018). The Finally, posts that were unrelated to (Table 1). The content of those sub- specific data preparation included seven hydroponic indoor gardening were reddits was systematically crawled steps: 1) tokenization (i.e., converting removed, and the number of OPs (i.e., methodically browsed) using individual characters into aggregate with no responses were counted. This a custom code developed with Java sets of characters) with removal of short task was accomplished by reading all
Table 1. Subreddit description as of 19 Nov. 2019 of four online communities from which original posts and primary comments/questions related to hydroponic indoor gardening were extracted and analyzed. Community Subreddits specifics r/hydro r/Hydroponics r/Urbanfarming r/Aerogarden Description A home for hydroponic A subset of hydroculture, This subreddit is for all Welcome to Reddit’s message gardeners, from the method of growing things urban farming, AeroGarden hobbyist to commercial plants without soil, using from news and pictures to community! Feel free to growers. Post grow mineral nutrient solutions advice and techniques, post things such as journals, questions, and in a water solvent. and at any scale, from progress pics, questions, discussions! a windowsill to a small advice, sales, or coupon business. codes, and videos. Age (years) 10 10 9 9 Subscribers (no.) 27,282 21,490 14,795 3,784 Moderators (no.) 6 4 n/a 1
• June 2020 30(3) 347 Table 2. Search words and/or concepts used to classify original posts related to hydroponic indoor gardening from the r/hydro, r/Hydroponics, r/UrbanFarming, and r/Aerogarden subreddit communities.z Cultural practices Seeding, sowing, transplanting, shoot pruning, root pruning, pollinating, harvesting, planting, training, grafting, staking, de-topping, pinching, sucker removal, lower leaf removal, de-suckering, propagating, plant support, supporting Plant material Cultivar, transplant, seed, cutting, vegetative, sexual, asexual, hardiness, determinate, indeterminate Root-zone environment Nutrient solutions, pH, electrical conductivity, EC, fertilizer formulations, organic, solution replacement, replenish, solution temperature, water temperature, slow-release, continuous-release, aeration, water-soluble, fertilizer, plant-food, bubbles, nano-bubbles, mist, root volume, root expansion, root space, nutrient mix, nutrients, reservoir water, nutrient content, masterblend, nutes, res, flush, water chiller, pH up, pH down, acid, base, alkaline, acidic Plant disorders Yellow, chlorosis, browning, necrosis, burning, deform, growing tip, stunted, slimy, brown roots, blossom-end rot, BER, fruit crack, blotchy, green shoulder, sunscald, crooking, flower abortion, fruit abortion, misshapen, protuberance, blister, indentation, catface, deficiency, toxicity, edema, oedema, intumescence, bump, lesion, salinity, excess, lack, viviparism Diseases Bacteria, bacterial disease, bacterial canker, bacterial speck, pseudomonas (Pseudomonas syringae), bacterial spot, xanthomonas (Xanthomonas axonopodis), bacterial wilt, erwinia (Erwinia tracheiphila), ralstonia (Ralstonia solanacearum), fungus, fungal disease, aspergillus (Aspergillus niger), mold, mould, black root rot, gray mold, botrytis (Botrytis cinerea), stem canker, root rot, damping off, early blight, Pythium (Pythium sp.), fusarium (Fusarium oxysporum), fusarium wilt, white mold, sclerotinia (Sclerotinia sp.), mildew, powdery mildew, virus, viral disease, tomato leaf curl virus, slime, slimy, foam, foamy Pests Sanitation, prevention, integrated pest management, IPM, thrips, biological control, biocontrol, leaf miner, mite, spider mite, aphid (Aphis sp.), whitefly (Bemisia tabaci), armyworm (Pseudaletia unipuncta), bloodworm (Glycera dibranchiata), cutworm (Agrotis ipsilon), fungus gnats (Bradysia sp.), moths, lepidoptera, looper (Trichoplusia ni), mealybug, Pseudococcidae, shore fly, slug, snail Environmental conditions Air flow/circulation, air temp, relative humidity, carbon dioxide, CO2, enrichment, HVAC, CO2 deficiency, CO2 drawdown, CO2 injector, mycelial CO2, liquid CO2, heat, cold, hot, warm, chilled Plant lighting Incandescent, fluorescent, light-emitting diode, LED, lamps, intensity, quality, quantity, white light, red light, blue light, green light, CWF, SPS, broadband, narrowband, plasma, metal halide, color, lightbulb, bulb, ultraviolet, radiation, plant stretching, spacing, headroom, wattage, photosynthetic photon flux, PPF, PPDF, closeness to plants, lumen, lux, watt Production system Setup, design, nutrient film technique, NFT, deep water culture, DWC, Dutch bucket, ebb and flood, ebb’n’flow, drip-pass, aeroponic, aquaponic, floating, raft, drip irrigation, substrate, rockwool, rock wool cube, inorganic, peatmoss, coco coir, perlite, vermiculite, rice hull, peatlite, mixes, bark chips, sawdust, sand, pellets, fogponics, wick, kratky, kratki, liquid system, liquid hydroponic system, aggregate system, aggregate hydroponic system, pump Others Multi-topic questions zScientific names of organisms are included in parentheses for clarification.
OPs and identifying the topic descrip- a single rater) assessment, resulting for accuracy using the following scale: tors present within each OP. Once in coefficients of 0.88 and 0.97, 1 = completely inaccurate; 2 = mostly manual classification was completed, respectively, which suggest that the inaccurate; 3 = 50% accurate; 4 = topic classification was validated by topic descriptors used in the manual mostly accurate; and 5 = completely randomly selecting 10% of OPs and classification were highly accurate accurate. An expert panel consisting reviewing all data using interrater (Tinsley and Weiss, 1975). The of a senior master student with over agreement (i.e., degree of agreement resulting dataset included 1617 OPs two years of experience with hydro- among different raters for topic clas- and 4891 primary comments/re- ponic indoor gardening, and a univer- sification) and intrarater reliability sponses to OPs. Comments for each sity professor with over 15 years of (i.e., consistency of classification by of the 10 topics were manually rated experience in controlled environment
348 • June 2020 30(3) agriculture rated comments based response to OPs across topics, which in the scientific literature can be con- on the accuracy scale. Additionally, ranged from 2.3 to 3.5 (Table 5). The fusing to nonhorticulturists, such as where rating was not obvious, infor- three topics with the highest percent- indoor gardeners (Jones, 2014). There- mation provided in the comments age of completely accurate responses, fore, although there is a vast amount of was corroborated using various scien- regardless of sample size, were dis- scientific information available related tific resources to ensure accurate rat- eases (40%), root-zone environment to hydroponic use for gardening pur- ing (e.g., Jones, 2005, 2014; Lopez (20%), and environmental conditions poses, the information may not be easy and Runkle, 2017). Examples of OPs (17%). In contrast, the topics with the to interpret by people with no formal with corresponding classification, lowest percentage of completely ac- training in plant production. topic descriptor, response accuracy curate responses were pests (0%), In contrast to the low percentage rating, and rating rationale are shown plant disorders (3%), and others of unanswered questions for the top in Table 3. Lastly, to identify relevant (4%). The three topics with the high- three topics, the topics pests, diseases, points of discussion about the most est percentage of comments that were and ‘‘others’’ had 32%, 25%, and 40% of common knowledge gaps, the top completely inaccurate were plant ma- unanswered questions, respectively (Fig. three topics based on post frequency terial (43%), plant disorders (23%), and 1). As previously described, the topic were subcategorized and inductively others (22%). The topics with the low- ‘‘others’’ included complex questions analyzed (Table 4). est percentage for completely inaccurate that were difficult to classify based on DATA ANALYSES. Sampled data responses were production system (4%), the topic descriptors (Table 2). Respon- used for the identification of each cultural practices (4%), and plant light- dents typically struggled with answering topic and subcategories for the top ing (7%). In general, 14% to 50% of multiple questions within one OP, or three topics were quantified with comments for OPs were rated as mostly questions that relied on visual aid for Microsoft Excel and graphed using inaccurate, 14% to 36% as 50% accurate, proper identification. Most responses in SigmaPlot (version 13.0; Systat Soft- and 7% to 28% as mostly accurate. the topic ‘‘others’’ requested additional ware, San Jose, CA). A one-way anal- background information and/or high- ysis of variance was conducted to test Discussion resolution photographs, and if OPs the hypothesis that the mean accuracy Based on our results, 50% of the were not updated, questions usually rating differed among topics. Group most common knowledge gaps among remained unanswered. The ability and means were compared using Tukey’s indoor gardeners are related to pro- willingnesstorespondtoOPsbyReddit honestly significant difference test at duction systems, plant lighting, and users seems to depend on question type P < 0.05 with statistical analysis soft- root-zone environment (Fig. 1). How- and on whether adequate background ware (JMP version 12; SAS Institute, ever, it is interesting to note that, informationisprovidedintheOP. Cary, NC). regardless of the number of OPs, these Thus, clear and concise questions within three topics had the lowest percentages OPs should help improve response rate Results of unanswered questions, ranging from and accuracy. OP CLASSIFICATION. Questions 5% to 14%. In addition, among the The most common questions made about the topics of production responses provided to OPs, accuracy of within the topic of production system systems (19%), plant lighting (17%), responses provided to questions related were about setups (43%) and general and root-zone environment (14%) to the topic of production system were design (39%) (Fig. 2). In addition, accounted for 50% of the total OPs equally distributed in the scale from 2 most OPs were related to do-it-your- (Fig. 1). The other 50% of questions to 4 (i.e., mostly inaccurate to mostly self (DIY) systems built and designed were distributed among all other accurate) (Table 5). Similarly, over 25% by indoor gardeners (data not seven topics, which included plant of responses for questions related to shown). In contrast, fewer OPs asked disorders (13%), cultural practices plant lighting and root-zone environ- questions about commercial counter- (10%), diseases (6%), plant material mentwereratedwithin2to3inthe top systems. While indoor gardeners (4%), environmental conditions (3%), accuracy scale. This suggests that, al- may rely on different system setups or pests (2%), and ‘‘others’’ (12%). Ex- though research-based information is designs, the cost difference between cept for the topic plant lighting, all available for indoor gardeners, misin- a DIY system built with raw materials topics had at least 10% of unanswered formation is likely being disseminated vs. a prefabricated commercial system OPs (Table 5). The subcategories and in these subreddits. can be large, with DIY systems typi- corresponding number of posts for Hobbyist gardeners struggle to cally being less expensive. Our data each of the three topics with the most discern between reliable or unreliable indicate that some of the most com- OPs (in parentheses) were: 1) pro- information available online (Jones, mon types of systems used by do-it- duction systems, with setup (115), 2014), some of which typically lacks yourselfers (also known as ‘‘DIYers’’) general design (104), and substrate a scientific basis. Even if gardeners are deep-water culture (DWC), (21); 2) plant lighting, with lamp type can identify reliable information, the nutrient film technique (NFT), ebb- (85), lamp intensity (71), and lamp terms and concepts used in research- and-flood, and vertical planters; aero- setup (63); and 3) root-zone environ- based literature tend to be considered ponic systems are used less frequently ment, with nutrient solution formu- overly technical (Schmitz, 2004). For (data not shown). Correspondingly, lation (118), water temperature (47), example, unstandardized units of mea- DWC, NFT, and ebb-and-flood sys- and pH balance (29) (Table 4, Fig. 2). surement (e.g., a mix of U.S. customary tems are frequently recommended for COMMENT RATINGS. There were units and metric units) and varying hobbyist gardeners (Jones, 2014; no significant differences among the terminology (e.g., references to essen- Resh, 2015), and closed-loop hydro- means of the accuracy rating in tial element, nutrient, and salts) found ponics in particular offer advantages
• June 2020 30(3) 349 Table 3. Examples of original posts and comments/responses related to hydroponic indoor gardening posted on the r/ hydro, r/Hydroponics, r/UrbanFarming, and r/Aerogarden subreddit communities with a corresponding topic descriptor and classification, comment accuracy rating, and rating rationale. The accuracy rating was based on a scale where 1 = completely inaccurate; 2 = mostly inaccurate; 3 = 50% accurate; 4 = mostly accurate; and 5 = completely accurate. Original post: ‘‘Any way to estimate or test the remaining contents of spent reservoir water?’’ Topic descriptor: Reservoir water; nutrient content Topic classification: Root-zone environment Comment: ‘‘Reach out to your local ag extension. The state university likely has a water lab running samples on some state-sponsored system to measure homeowners well water. You want an esi mass spec to measure everything at once, but that will cost you a couple k, or you can do old-fashioned chemistry and titer in a redox indicator with an eyedropper until you see a color shift. I don’t remember what reagents those are, but you probably did it in chemistry laboratory in high school.’’ Accuracy rating: 5 Rationale: The comment suggests that the original poster must seek professional advice. However, it proposes chemistry measures that would be unrealistic for most indoor gardeners (italics). Regardless of feasibility, the response provided is accurate for the question. Original post: ‘‘Help! What are these deformities/blisters on my tomato leaves? I have a DWC system, any tips on clearing them up?’’ Topic descriptor: Blisters, deformities (based on pictures provided) Topic classification: Plant disorders Comment: ‘‘Probably edema, lowering humidity and decreasing watering should help.’’ Accuracy rating: 4 Rationale: The comment provides an answer to both inquiries in the original post (OP). However, it proposes an inappropriate watering strategy considering that a deep-water culture hydroponic system is being used (italics). Therefore, although the response provided is accurate, it is not entirely correct. Original post: ‘‘What are these? First timer here! These are my first seedlings and all of my seedlings look fine, except my basil has this mucus-looking layer on them. Not sure what they are, and not sure what to search to correct it. Any help would be great.’’ Topic descriptor: Identification/questions about seeds (based on pictures provided) Topic classification: Plant material Comment: ‘‘They are basil seeds, totally normal. Just overseeded, which is a good thing.’’ Accuracy rating: 3 Rationale: The comment answers the questions asked in the OP. However, it also provides inaccurate advice for sowing basil seed (italics). Original post: ‘‘On the terrifyingly complicated topic of lighting: it seems that blue-red-purple lights are superior, yes? I almost bought a 20,000 lumen, 4-foot-long, 4-tubes LED thing for $110 on Amazon, but after much reading, I settled for a blue-red-purple 4-foot-long light at $68. Was I right? Wrong? Or doesn’t it matter?’’ Topic descriptor: LED lamps, red, blue, lumen Topic classification: Plant lighting Comment: ‘‘Blue/red tends to be cheaper and more efficient, but I wouldn’t say better. Maybe better for a beginner. There are certainly plants out there that don’t like blue/red as much as white (and others that don’t care at all). The bigger issue for your first few plants is to just get enough light. LEDs, CFLs, whatever, just get enough photon flux that your plants will grow. The color is 10x less important than just having enough.’’ Accuracy rating: 2 Rationale: Most of the information provided is incorrect (italics). Original post: ‘‘Spider mites got into my indoor gardens. I’ve been spraying organic insecticidal soap like crazy to try and get rid of them. My gardens are right by where I work, so I can’t do anything too rash. Any advice or help?’’ Topic descriptor: Spider mites Topic classification: Pests Comment: ‘‘Try a pyrethrin-based pesticide, it degrades in a couple of days.’’ Accuracy rating: 1 Rationale: The comment provides inaccurate information because it suggests a pest control strategy that is not recommended for plant production under limited light and ventilation, such as that of plants found indoors. Because the half-life of pyrethrin under these conditions can extend up to 17 d, the response is not accurate in relation to the background information provided or the question asked (National Pesticide Information Center, 2014).
350 • June 2020 30(3) Table 4. Search words/concepts used to subcategorize original posts related to hydroponic indoor gardening from the r/ hydro, r/Hydroponics, r/UrbanFarming, and r/Aerogarden subreddit communities pertaining to the three topics with the highest frequency of questions. Topic Subcategory Search words/concepts Production system Setup Setup for existing plants, general setup, NFT, DWC, Dutch buckets, ebb’n’flow, drip-pass, aeroponic, aquaponic, floating, raft, drip irrigation, fogponics, deep-water culture, ebb’n’flood, wick, kratky, kratki, pump General design Design for future plants, aggregate hydroponic system, liquid system, liquid hydroponic system, aggregate system Substrate Rockwool, rock wool cube, inorganic, peat moss, coco coir, perlite, vermiculite, rice hulls, peatlite mixes, bark chips, sawdust, sand, pellets Plant lighting Lamp type Incandescent, fluorescent, LED lamps, quality, white light, red light, blue light, green light, CWF, SPS, broadband, narrowband, plasma, metal headlight, color, light bulb, ultraviolet Lamp intensity Intensity, quantity, wattage Lamp setup Spacing, headroom, closeness to plants Root-zone environment Nutrient solution Nutrient solutions, EC, fertilizer formulations, organic production, nutrient formulation solution replacements, slow-release, continuous-release, water-soluble, fertilizer, plant-food, nutrient mix, nutrient, nutrient content, masterblend fertilizer, nutes, res Water temperature Solution temperature, water temperature, water chiller pH balance Question focused on pH, pH up, pH down, acid, base, alkaline, acidic
for significantly less time than most other hydroponic systems (Gopinath et al., 2017). Over 85% of OPs related to plant lighting were indicative of knowledge gaps related to lamp type, intensity needed for sole-source lighting, or lamp setup (Fig. 2). Although most lamp fixtures have been designed for human use, recent developments with light-emitting diode (LED) technol- ogy have enabled companies to design ‘‘horticultural-grade’’ lamps (Both et al., 2017). However, the widespread use of LED lamps has contributed to the significant confusion about plant responses to light quantity and quality. For example, claims about light sources that can ‘‘optimize’’ indoor plant pro- duction may be disseminating mislead- ing information. That is because a general conclusion from plant light- ing research with LEDs indicates that plant responses to the different light properties are highly dependent on many biological and environmental factors and thus, an ‘‘optimal’’ recipe for all crops and production purposes is unlikely to exist (Bugbee, 2016; Mitchell Fig. 1. Frequency of answered and unanswered questions for original posts and Sheibani, 2020). related to hydroponic indoor gardening from the r/hydro, r/Hydroponics, Many questions in the OPs were r/UrbanFarming, and r/Aerogarden subreddit communities grouped into 10 related to LED use, with fewer men- topics. tions of high-pressure sodium or fluo- rescent lamps (data not shown). In when there are space limitations, which of preference for aeroponics can be addition, one of the most recurring is a general consideration among attributed to the limited informa- remarks within OPs was the search for indoor gardeners (Solis-Toapanta tion available for these systems, as a low-cost lamp that would provide et al., 2020). It is likely that the lack they have been commercially available enough light for sole-source lighting.
• June 2020 30(3) 351 Table 5. Summary statistics and characterization of response (resp.) accuracy to original posts (OPs) related to hydroponic indoor gardening from the r/hydro, r/Hydroponics, r/UrbanFarming, and r/Aerogarden subreddit communities. Response accuracy was determined based on an accuracy scale rating, where 1 = completely inaccurate; 2 = mostly inaccurate; 3 = 50% accurate; 4 = mostly accurate; and 5 = completely accurate. Accuracy scale 12345 OPs with Mean Topicsz Responses (% of total) Resp. (no.) resp. (%) accuracy scale Production system 4y 28 28 28 12 503 86 3.2 ax Plant lighting 7 37 35 7 14 281 95 2.4 a Root-zone environment 11 33 27 7 20 904 90 2.8 a Plant disorders 23 36 31 8 3 788 83 2.3 a Cultural practices 4 24 36 20 16 306 84 3.5 a Diseases 13 20 14 13 40 122 75 2.8 a Plant material 43 14 21 8 14 864 80 2.8 a Environmental conditions 17 33 17 16 17 501 82 3.2 a Pests 12 50 25 13 0 462 68 2.6 a Others 22 22 35 17 4 160 60 2.4 a zTopics are listed in descending order based on total number of posts. yValues within rows depict the distribution of completely inaccurate to completely accurate responses provided to the OPs for each topic. xMeans within column followed by the same letter are not different based on Tukey’s honestly significant difference test at P £ 0.05.
Fig. 2. Frequency of posted questions relevant to three subcategories related to hydroponic indoor gardening from the r/hydro, r/Hydroponics, r/UrbanFarming, and r/Aerogarden subreddit communities.
A large portion of the OPs suggest require more light than leafy greens, photometric units such as lumens, there is considerable confusion about and thus, such crops may need a differ- lux, and foot-candles (Both et al., the minimum amount of light re- ent light source capable of providing 2017; Halleck, 2018). Nonetheless, quired to produce both leafy greens the minimum light threshold for pro- peer-reviewed and outreach materials and fruiting crops indoors. Con- duction (Dorais et al., 2017). None- that explain the importance of mea- sidering that most indoor gardeners theless, to our knowledge, no research suring light used by plants (e.g., pho- want inexpensive lamps, off-the-shelf has evaluated light requirements for tosynthetic photon flux, daily light LED lamp fixtures could be a suitable indoor gardening of fruiting crops; integral) are readily available to the sole-source lighting option, as they thus, specific recommendations are still general public (Runkle, 2015, 2018). have been shown to provide sufficient unknown. It was interesting to note that correct light to maintain pick-and-eat leafy Additionally, indoor gardeners terms for the topic of plant lighting, greens within indoor environments struggle to correctly interpret and such as the ones given in the previous (Paz et al., 2019; Solis-Toapanta and make use of appropriate light units for example, were used fewer than 10 times Gomez, 2019). However, fruiting crops plant production and typically rely on in the entire dataset (data not shown).
352 • June 2020 30(3) Questions in OPs about lamp their own nutrient solution daunting, been published in journals with a fee- setups primarily asked about the and they could benefit from pre- based subscription. However, with number of lamps needed to provide mixed commercial formulations for the rapid changes in academic pub- enough light, or about the most suit- general use. Nonetheless, it is impor- lishing and science communication, able spacing between plants and tant to consider that using commer- open access journals continue to be- lamps. Although these questions be- cially available nutrient solutions may come popular because they enable long to the subcategory of lamp not be infallible, as additional factors scientists to increase their reader base setup, it is likely that the difficulty such as solution temperature and and communicate research-based experienced by indoor gardeners water pH may affect the success rate findings with larger audiences (Oster- originates from the existing misinfor- of hydroponic production. Consider- rieder, 2013; Piwowar et al., 2018). mation about appropriate lamp types ing that most indoor gardeners prefer According to Archambault et al. and intensities. As previously de- closed-loop hydroponic systems that (2014), open access articles published scribed, there is much confusion sur- require constant monitoring and han- in peer-reviewed journals will soon rounding sole-source lighting, which dling, coupled with the presumption overcome paywalled literature. There- often leads to mistakes that could that they struggle with understanding fore, to ensure that appropriate audi- result in unsuccessful indoor garden- nutrient solution formulations, it is ences (e.g., indoor gardeners and ing experiences. Although there are likely that challenges with proper product suppliers) benefit from re- many websites, outreach articles, and solution management contribute to search findings relevant to indoor gar- research-based information about plant unsuccessful indoor gardening expe- dening, open access journals should be lighting, the main questions identified riences with hydroponics. considered as the primary outlet for in this study illustrate how indoor According to Jones (2014), peer-reviewed publications in this area. gardeners struggle to find and make when growing plants hydroponically, In addition, close collaboration between use of consistent and accurate infor- nutrient solution temperature should researchers and extension professionals mation about this topic. be maintained similar to ambient tem- is critical to facilitate the delivery of Among the subcategories identi- perature to ensure optimal plant growth outreach materials to lay audiences in- fied within the topic of root-zone (assuming temperature ranges are not terested in indoor gardening. environment, most OPs were related limiting). However, the most frequent In conclusion, the widespread to nutrient solution formulation advice provided in response to OPs use of social media can provide a quick (56%), water temperature (23%), and encouraged Reddit users to cool down and responsive network to gather and pH balance (14%) (Fig. 2). Nutrient the nutrient solution, regardless of air exchange information among science solution formulation is one of the most temperature, an action that could affect communicators and the general pub- misunderstood aspects of growing overall plant health and productivity lic. Data mining tools enabled the plants hydroponically by indoor gar- (Jones, 2014). Finally, although identification of common knowledge deners, considering that most literature most OPs within the topic of root- gaps among online communities dis- islimitedtoprovidingnutrientsolu- zone environment mentioned pH, cussing hydroponic indoor garden- tion recipes for crops commonly there seems to be a significant lack of ing. Results from this study indicate grown commercially (Jones, 2014; understanding about the importance of that most posts from four subreddits Solis-Toapanta et al., 2020). Few pH management in hydroponic pro- focused on hydroponic indoor gar- hobbyist gardeners understand the duction. Most of the available literature dening relate to confusions regarding complex relationship between the that refers to optimal pH ranges orig- the design and implementation of composition, concentration, and rate inates from studies conducted to de- appropriate hydroponic production at which plants use the elements pres- termine nutrient availability (Argo systems. In addition, misinformation ent in nutrient solutions, particularly and Fisher, 2003; Jones, 2001; Dick- about plant lighting seems to be in closed-loop hydroponic systems. son and Fisher, 2019). However, the a major part of discussions about For example, scientists tend to recom- effects of water quality on solution growing plants indoors. There is also mend adjusting the concentration of pH, electrical conductivity, and alka- limited understanding about nutrient nutrients within hydroponic nutrient linity is an important consideration solution management, particularly solutions depending on the different for hydroponic indoor gardeners, about fertilizer formulation, pH bal- plant growth stages (e.g., seedling, particularly when periodically replen- ance, and on the impact that solution vegetative, or reproductive) (Bugbee, ishing systems with tap water. There- temperature has on plant growth and 2004). Nonetheless, hydroponic plants fore, it is important for nutrient development. In general, there were can be grown with an array of solu- solution formulations to be adaptable no differences among response tion formulations such as those of to a wide array of water qualities, as accuracy for all analyzed topics. How- Hoagland and Arnon (1950), Muckle they will directly influence the garden- ever, regardless of topic, responses (1993), and Yuste and Gostincar ing experience. for most OPs had less than 50% (1999), among others. Although A possible explanation to the accuracy, which demonstrates that there is substantial research-based high frequency of OPs asking ques- misinformation can be disseminated information about nutrient solution tions about indoor plant production in social media. Based on the fre- management in hydroponics (Bug- may be related to the limited accessi- quency and type of questions posted bee, 2004; Christie, 2014; Trejo- bility to research-based information, on Reddit about hydroponic plant Tellez and Gomez-Merino, 2012), because scientific findings relevant to production indoors, there is an op- inexperienced indoor gardeners hydroponics and controlled-environ- portunity to address knowledge gaps might find the task of formulating ment plant production have generally with targeted open access research
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