Pickens, J., da Silva, A., and Ayipio, E. Transplant Production for Hydroponic and Greenhouse Systems. ANR-2954. Alabama Cooperative Extension System, 2023.
Used in: Lesson 26
Hooks, T. Module 3: Hydroponic Nutrient Solutions. Greenhouse Hydroponic Tomato Workshop, University of Arizona Controlled Environment Agriculture Center, 2026.
Used in: Lesson 11
Help with yellow leaves. Ask Extension, answered by Michigan State University Extension, 2024.
https://ask.extension.org/kb/faq.php?id=890658
Used in: Lesson 14
Chappell, J. A. Nitrite Poisoning or Brown Blood Disease: A Preventable Problem. Auburn University, 2008.
Barbosa, G. L., Gadelha, F. D. A., Kublik, N., Proctor, A., Reichelm, L., Weissinger, E., Wohlleb, G. M., and Halden, R. U. Comparison of Land, Water, and Energy Requirements of Lettuce Grown Using Hydroponic vs. Conventional Agricultural Methods. International Journal of Environmental Research and Public Health 12(6): 6879-6891, 2015.
U.S. Bureau of Labor Statistics. Agricultural Engineers. Occupational Outlook Handbook.
https://www.bls.gov/ooh/architecture-and-engineering/agricultural-engineers.htm
Used in: Lesson 26
U.S. Bureau of Labor Statistics. Agricultural and Food Scientists. Occupational Outlook Handbook.
https://www.bls.gov/ooh/life-physical-and-social-science/agricultural-and-food-scientists.htm
Used in: Lesson 26
U.S. Bureau of Labor Statistics. Farmers, Ranchers, and Other Agricultural Managers. Occupational Outlook Handbook.
https://www.bls.gov/ooh/management/farmers-ranchers-and-other-agricultural-managers.htm
Used in: Lesson 26
Doubrava, N., and Polomski, R. F. Leaf and Needle Drop. HGIC 2353. Clemson Cooperative Extension, Home and Garden Information Center, updated 2019.
https://hgic.clemson.edu/factsheet/leaf-needle-drop/
Not used by a published lesson yet.
Shaughnessy, D., and A. Pertuit. Indoor Plants: Cleaning, Fertilizing, Containers & Light Requirements. HGIC 1450. Clemson Cooperative Extension Home & Garden Information Center, 1999.
https://hgic.clemson.edu/factsheet/indoor-plants-cleaning-fertilizing-containers-light-requirements/
Used in: Lesson 5
Colorado State University Extension. Root Disease Problems and Management in Hydroponic Systems. PlantTalk Colorado 2043.
Used in: Lesson 12
Card, A., D. Whiting, C. Wilson, J. Reeder, and D. Goldhamer. Plant Nutrition. GardenNotes no. 231. Colorado State University Extension, 2015 (reviewed 2023).
https://extension.colostate.edu/resource/plant-nutrition/
Used in: Lesson 4
Brechner, M., and Both, A. J. Hydroponic Lettuce Handbook. Cornell Controlled Environment Agriculture, 2013.
https://cea.cals.cornell.edu/files/2019/06/Cornell-CEA-Lettuce-Handbook-.pdf
Used in: Lesson 12
Cool Season Vegetables. Cornell Cooperative Extension of Monroe County.
https://monroe.cce.cornell.edu/resources/cool-season-veggies
Used in: Lesson 20
Cornell AgriTech. Plant Breeding. Cornell University College of Agriculture and Life Sciences.
https://cals.cornell.edu/cornell-agritech/our-expertise/plant-breeding
Used in: Lesson 26
Cornell Small Farms Program. Roof Top Gardening. Guide to Urban Farming. Cornell University College of Agriculture and Life Sciences.
https://smallfarms.cornell.edu/resources/guide-to-urban-farming/roof-top-gardening/
Used in: Lesson 25
Mattson, N. Testing Container Media. Cornell University.
https://dlc.cce.cornell.edu/pluginfile.php/342377/mod_page/content/36/Media%20testing.pdf
Used in: Lesson 11
Saupe, S. G. Willows and Photosynthesis: Analyzing van Helmont's Classic Experiment. Concepts of Biology (BIOL115), College of St. Benedict/St. John's University, 2004.
https://employees.csbsju.edu/SSAUPE/biol115/van_helmont.htm
Used in: Lesson 2
Grow Easy. College of Tropical Agriculture and Human Resources, University of Hawaii, 2019.
https://cms.ctahr.hawaii.edu/News/ArtMID/48015/ArticleID/990/Grow-Easy
Used in: Lesson 8
Kratky, B. A. Fertilizer Stock Solutions: For Lettuce. University of Hawaii CTAHR.
https://www3.ctahr.hawaii.edu/Hawaii/downloads/Fertilizer_Stock_Solutions_for_lettuce.pdf
Used in: Lesson 9
Kratky, B. A. A suspended pot, non-circulating hydroponic method. Acta Horticulturae 648: 83-89, 2004.
https://www3.ctahr.hawaii.edu/hawaii/downloads/A_Suspended_Pot_Non-circulating_Hydroponic_Method.pdf
Used in: Lesson 12
Kratky, B. A. A Simple Hydroponic Growing Kit for Short-Term Vegetables. Home Garden HG-42. College of Tropical Agriculture and Human Resources, University of Hawaii, 2002.
https://www3.ctahr.hawaii.edu/oc/freepubs/pdf/HG-42.pdf
Used in: Lesson 15
Kratky, B. A. A Suspended Net-Pot, Non-Circulating Hydroponic Method for Commercial Production of Leafy, Romaine, and Semi-Head Lettuce. Vegetable Crops VC-1. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, 2010.
Fisheries and Oceans Canada. Don't let it loose.
https://www.dfo-mpo.gc.ca/species-especes/ais-eae/prevention/dlil-nlrp-eng.html
Used in: Lesson 20
Mattson, N., and T. Merrill. Symptoms of Common Nutrient Deficiencies in Hydroponic Lettuce. e-GRO Research Update no. 2015.09, October 2015.
https://www.e-gro.org/pdf/Mattson_Lettuce_2015_9.pdf
Used in: Lesson 14
Houston, L., Dickson, R., and Machesney, L. Fine-tuning nutrient replenishment in hydroponics. e-GRO Edible Alert 6(11), 2021.
https://www.e-gro.org/pdf/E611.pdf
Used in: Lesson 11
Williams-Woodward, J. Root disease management in hydroponic systems. e-GRO Alert 7(6), 2022.
https://greenhousehort.mgcafe.uky.edu/sites/greenhousehort.ca.uky.edu/files/E706.pdf
Used in: Lesson 12
U.S. Environmental Protection Agency. 5.2 Dissolved Oxygen and Biochemical Oxygen Demand. Volunteer Stream Monitoring: A Methods Manual (archived).
https://archive.epa.gov/water/archive/web/html/vms52.html
Used in: Lesson 12
U.S. Environmental Protection Agency. Sources and Solutions: Agriculture. Nutrient Pollution.
https://www.epa.gov/nutrientpollution/sources-and-solutions-agriculture
Used in: Lesson 24
U.S. Environmental Protection Agency. What is pH?
https://www.epa.gov/goldkingmine/what-ph
Used in: Lesson 10
Somerville, C., Cohen, M., Pantanella, E., Stankus, A. and Lovatelli, A. Small-scale aquaponic food production: Integrated fish and plant farming. FAO Fisheries and Aquaculture Technical Paper No. 589. Food and Agriculture Organization of the United Nations, Rome, 2014.
Used in: Lesson 10, Lesson 12, Lesson 16, Lesson 17, Lesson 18, Lesson 19, Lesson 20, Lesson 21, Lesson 22, Lesson 23
FAO. AQUASTAT - FAO's Global Information System on Water and Agriculture: Water use. Food and Agriculture Organization of the United Nations.
https://www.fao.org/aquastat/en/overview/methodology/water-use/
Used in: Lesson 24
Ayers, R. S., and Westcot, D. W. Water quality for agriculture. FAO Irrigation and Drainage Paper 29 Rev. 1. FAO, 1985. Section 2.3, Salinity effects on crops.
https://www.fao.org/4/t0234e/T0234E02.htm
Used in: Lesson 11
Shell, H. R. "van Helmont, Jan." Plant Sciences. Gale, via Encyclopedia.com.
https://encyclopedia.com/science/news-wires-white-papers-and-books/van-helmont-jan
Used in: Lesson 2
Hoagland, D. R., and D. I. Arnon. The Water-Culture Method for Growing Plants without Soil. Circular 347. University of California College of Agriculture, Agricultural Experiment Station, 1938.
https://ia801405.us.archive.org/24/items/waterculturemeth347hoag/waterculturemeth347hoag.pdf
Gillespie, D. P., Kubota, C., and Miller, S. A. Effects of low pH of hydroponic nutrient solution on plant growth, nutrient uptake, and root rot disease incidence of basil (Ocimum basilicum L.). HortScience 55(8): 1251-1258, 2020.
Used in: Lesson 10
Fitriyah, H., Budi, A. S., Maulana, R., and Setiawan, E. Controlling the Nutrition Water Level in the Non-Circulating Hydroponics based on the Top Projected Canopy Area. IJCCS 16(2), 2022.
https://journal.ugm.ac.id/ijccs/article/view/70556
Used in: Lesson 12
Johnson, K. Growing without soil: Getting started with hydroponics at home. Good Growing blog, University of Illinois Extension, 2026.
Grow Herbs and Lettuce Indoors this Winter. Good Growing blog, University of Illinois Extension, 2017.
https://extension.illinois.edu/blogs/good-growing/2017-11-17-grow-herbs-and-lettuce-indoors-winter
Not used by a published lesson yet.
Hart, C. Home Hydroponics (handouts). University of Illinois Extension.
https://extension.illinois.edu/sites/default/files/illinois_extension_hydroponics_handouts.pdf
Steil, A. What's the difference between cool and warm season veggies? Yard and Garden, Iowa State University Extension and Outreach, 2025.
Used in: Lesson 1
Steil, A. Sources of Supplemental Light for Indoor Plants. Yard and Garden, Iowa State University Extension and Outreach (reviewed 2023).
Used in: Lesson 5
Paracueles, C. N. L. Toxicity of Ammonia on Oreochromis niloticus Fingerlings. Journal of Environment and Aquatic Resources, Mindanao State University at Naawan, 2015.
Used in: Lesson 22
Singh, H., Dunn, B., and Payton, M. Hydroponic pH modifiers affect plant growth and nutrient content in leafy greens. Journal of Horticultural Research 27(1): 31-36, 2019.
https://reference-global.com/download/article/10.2478/johr-2019-0004.pdf
Used in: Lesson 10
Khodadad, C. L. M., Hummerick, M. E., Spencer, L. E., Dixit, A. R., Richards, J. T., Romeyn, M. W., Smith, T. M., Wheeler, R. M., and Massa, G. D. Microbiological and Nutritional Analysis of Lettuce Crops Grown on the International Space Station. Frontiers in Plant Science 11, 2020. doi:10.3389/fpls.2020.00199.
https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00199/full
Used in: Lesson 25
Klepper, B., and M. R. Kaufmann. Removal of Salt from Xylem Sap by Leaves and Stems of Guttating Plants. Plant Physiology 41(10): 1743-1747, 1966.
https://pmc.ncbi.nlm.nih.gov/articles/PMC550602
Used in: Lesson 6
Kratky, B. A. Three non-circulating hydroponic methods for growing lettuce. Acta Horticulturae 843: 65-72, 2009. Copy hosted by the University of Hawaii CTAHR.
Used in: Lesson 7, Lesson 8, Lesson 9, Lesson 12, Lesson 14, Lesson 15
Rogers, D., Lamm, F., Alam, M., Trooien, T., Clark, G., Barnes, P., and Mankin, K. Efficiencies and Water Losses of Irrigation Systems. MF2243. Kansas State University Research and Extension.
https://bookstore.ksre.ksu.edu/download/efficiencies-and-water-losses-of-irrigation-systems_MF2243
Used in: Lesson 24
Lanoue, J., J. Zheng, C. Little, A. Thibodeau, B. Grodzinski, and X. Hao. Alternating Red and Blue Light-Emitting Diodes Allows for Injury-Free Tomato Production With Continuous Lighting. Frontiers in Plant Science 10: 1114, 2019.
https://www.frontiersin.org/articles/10.3389/fpls.2019.01114/full
Used in: Lesson 5
Lin, C., T. Zhu, L. L. Peralta Ogorek, Y. Wang, M. Sauter, and O. Pedersen. The Pyramiding of Three Key Root Traits Aid Breeding of Flood-Tolerant Rice. Plants 11(15): 2033, 2022.
https://pmc.ncbi.nlm.nih.gov/articles/PMC9370703/
Used in: Lesson 3
Matsuda, R., N. Ozawa, and K. Fujiwara. Effects of Continuous Lighting with or without a Diurnal Temperature Difference on Photosynthetic Characteristics of Tomato Leaves. Acta Horticulturae 956: 165-170, 2012.
https://ishs.org/ishs-article/956_16/
Used in: Lesson 5
Schwarcz, J. The Powder of Sympathy. McGill University Office for Science and Society, 2022.
https://mcgill.ca/oss/node/9037
Used in: Lesson 2
MedlinePlus, U.S. National Library of Medicine. Bacterial Infections.
https://medlineplus.gov/bacterialinfections.html
Used in: Lesson 17
Meng, Q., and E. S. Runkle. Blue Photons from Broad-Spectrum LEDs Control Growth, Morphology, and Coloration of Indoor Hydroponic Red-Leaf Lettuce. Plants 12(5): 1127, 2023.
https://pmc.ncbi.nlm.nih.gov/articles/PMC10005505/
Used in: Lesson 5
Cabrera-Garcia, J., Milhollin, R., and Ernst, M. Controlled Environment Agriculture: Hydroponic Farming. G6986. University of Missouri Extension, 2024.
Cabrera-Garcia, J. Hydroponic Nutrient Solutions. Publication G6984. University of Missouri Extension.
Li, H., Parcell, J., Roach, A., Solomon, A., Cabrera-Garcia, J., Dietterle, L., and Spell, A. The Economics and Optimal Design of Missouri Indoor Farming Supply Chains. University of Missouri Extension.
Starbuck, C. J. Guttation: A Pressure Relief for Plants. Missouri Environment & Garden, Integrated Pest Management, University of Missouri, 2009.
https://ipm.missouri.edu/meg/2009/6/Guttation-A-Pressure-Relief-for-Plants/index.cfm
Used in: Lesson 6
Trinklein, D. Wet Weather Woes. Integrated Pest Management, University of Missouri, 2015.
https://ipm.missouri.edu/meg/2015/6/Wet-Weather-Woes/index.cfm
Used in: Lesson 3
Trinklein, D. H. Lighting Indoor Houseplants. G6515. University of Missouri Extension, revised 2017.
https://extension.missouri.edu/publications/g6515
Used in: Lesson 5
Geist, L. Too Much Moisture Can Hinder Root Development. University of Missouri Extension, 2025.
https://extension.missouri.edu/news/too-much-moisture-can-hinder-root-development
Used in: Lesson 12
Center for Biofilm Engineering, Montana State University. Biofilm Basics.
https://biofilm.montana.edu/biofilm-basics/index.html
Used in: Lesson 17
Jones, C., and K. Olson-Rutz. Plant Nutrition and Soil Fertility. Nutrient Management Module No. 2, 4449-2. Montana State University Extension, 2016.
https://landresources.montana.edu/nm/documents/soilmodulepdf/4449-2.pdf
Herridge, L. New Plant Habitat Will Increase Harvest on International Space Station. NASA, 2 March 2017.
Herridge, L. NASA Plant Researchers Explore Question of Deep-Space Food Crops. NASA, 17 February 2016.
Used in: Lesson 25
NASA. Growing Plants in Space. Page last updated 8 December 2023.
https://www.nasa.gov/exploration-research-and-technology/growing-plants-in-space/
Used in: Lesson 25
Massa, G. D. Veggie: Space Vegetables for the International Space Station and Beyond. NASA Kennedy Space Center, 2016. NASA Technical Reports Server 20160004060.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160004060.pdf
Used in: Lesson 25
NASA Science. Unearthly Plumbing Required for Plant Watering in Space. 20 May 2025.
Used in: Lesson 25
NASA International Space Station Research Integration Office. So You Want to Be a Space Farmer. 22 July 2022.
https://www.nasa.gov/missions/station/so-you-want-to-be-a-space-farmer/
Used in: Lesson 25
NASA International Space Station Research Communications Team. Space Gardens. 18 December 2024.
https://www.nasa.gov/missions/station/iss-research/space-gardens/
Used in: Lesson 25
NASA. STEMonstrations: Surface Tension. Classroom guide.
https://nasa.gov/sites/default/files/atoms/files/stemonstrations_surface-tension.pdf
Used in: Lesson 25
Herridge, L. Veggie Plant Growth System Activated on International Space Station. NASA, 16 May 2014.
Used in: Lesson 25
NASA. Veggie. NASA Facts.
https://www.nasa.gov/wp-content/uploads/2023/03/veggie-fact-sheet-508.pdf
Welch, N. Project Examines How to Water Plants in Space. NASA, 13 May 2021.
https://www.nasa.gov/humans-in-space/project-examines-how-to-water-plants-in-space/
Used in: Lesson 25
Daims, H., Lebedeva, E. V., Pjevac, P., Han, P. et al. Complete nitrification by Nitrospira bacteria. Nature 528, 504-509 (2015).
https://pmc.ncbi.nlm.nih.gov/articles/PMC5152751
Used in: Lesson 18
van Kessel, M. A. H. J., Speth, D. R., Albertsen, M., Nielsen, P. H., Op den Camp, H. J. M., Kartal, B., Jetten, M. S. M. and Lücker, S. Complete nitrification by a single microorganism. Nature 528, 555-559 (2015).
https://pmc.ncbi.nlm.nih.gov/articles/PMC4878690
Used in: Lesson 18
Moore, K. A., and L. K. Bradley, eds. "3. Botany." North Carolina Extension Gardener Handbook, 2nd ed. NC State Extension, AG-831, 2022.
https://content.ces.ncsu.edu/extension-gardener-handbook/3-botany
Gatiboni, L. "1. Soils & Plant Nutrients." In Moore, K. A., and L. K. Bradley, eds. North Carolina Extension Gardener Handbook, 2nd ed. NC State Extension, AG-831, 2022.
https://content.ces.ncsu.edu/extension-gardener-handbook/1-soils-and-plant-nutrients
Used in: Lesson 1, Lesson 2, Lesson 4, Lesson 7, Lesson 9, Lesson 14
Prasad, L., and Meehan, M. Using Electrical Conductivity and Total Dissolved Solids Meters to Field Test Water Quality. WQ1923. NDSU Extension.
Used in: Lesson 11
National Human Genome Research Institute. Talking Glossary of Genomic and Genetic Terms: Bacteria.
https://www.genome.gov/genetics-glossary/Bacteria
Used in: Lesson 17
Sallenave, R., and Shultz, R. C. Hydroponics: Water-saving Farming for New Mexico's Arid Environment. Guide H-180. New Mexico State University, College of Agricultural, Consumer and Environmental Sciences, 2022.
Sallenave, R. (revised by). Growing Trout in New Mexico Ponds. Guide L-108. New Mexico State University Cooperative Extension Service.
https://pubs.nmsu.edu/_l/L108.pdf
Used in: Lesson 20
Sallenave, R. Understanding and Preventing Fish Kills in Your Pond. Guide W-105. New Mexico State University, College of Agricultural, Consumer and Environmental Sciences.
https://pubs.nmsu.edu/_w/W105/
Used in: Lesson 22
Wilted plants with lots of water. Southwest Yard & Garden. New Mexico State University, College of Agricultural, Consumer and Environmental Sciences, 2006.
National Oceanic and Atmospheric Administration. Calcium nitrate. CAMEO Chemicals.
https://cameochemicals.noaa.gov/chemical/2785
Used in: Lesson 9
NOAA National Ocean Service. What is eutrophication?
https://oceanservice.noaa.gov/facts/eutrophication.html
Used in: Lesson 24
NOAA National Ocean Service. What causes nutrient pollution? Coastal Pollution Tutorial.
https://oceanservice.noaa.gov/education/tutorial-coastal/harmful-algal-blooms/habs01-sub-02.html
Used in: Lesson 24
U.S. National Park Service. Deserts. Science of the American Southwest.
https://www.nps.gov/subjects/swscience/deserts.htm
Used in: Lesson 25
Gillespie, D. Root Zone Management of Hydroponic Leafy Greens. Handout, Greenhouse Short Course, The Ohio State University, 2019.
Used in: Lesson 12
Singh, H., and Dunn, B. Electrical Conductivity and pH Guide for Hydroponics. HLA-6722. Oklahoma State University Extension, 2016.
https://pods.okstate.edu/fact-sheets/HLA-6722pod.pdf
Used in: Lesson 11
Deer, C., Hu, B., Dunn, B. and Dusci, J. Nitrification and Maintenance in Media Bed Aquaponics. Fact sheet HLA-6729. Oklahoma Cooperative Extension Service, Oklahoma State University, October 2021.
https://pods.okstate.edu/fact-sheets/HLA-6729.pdf
Used in: Lesson 16, Lesson 17, Lesson 18, Lesson 19, Lesson 21, Lesson 22, Lesson 23
Clark, M. A., M. Douglas, and J. Choi. "8.2 The Light-Dependent Reactions of Photosynthesis." Biology 2e. OpenStax, 2018.
https://openstax.org/books/biology-2e/pages/8-2-the-light-dependent-reactions-of-photosynthesis
Used in: Lesson 5
Clark, M. A., M. Douglas, and J. Choi. "8.1 Overview of Photosynthesis." Biology 2e. OpenStax, 2018.
https://openstax.org/books/biology-2e/pages/8-1-overview-of-photosynthesis
Clark, M. A., M. Douglas, and J. Choi. "31.1 Nutritional Requirements of Plants." Biology 2e. OpenStax, 2018.
https://openstax.org/books/biology-2e/pages/31-1-nutritional-requirements-of-plants
Used in: Lesson 4
Clark, M. A., M. Douglas, and J. Choi. "30.3 Roots." Biology 2e. OpenStax, 2018.
https://openstax.org/books/biology-2e/pages/30-3-roots
Used in: Lesson 6
Clark, M. A., M. Douglas, and J. Choi. "30.5 Transport of Water and Solutes in Plants." Biology 2e. OpenStax, 2018.
https://openstax.org/books/biology-2e/pages/30-5-transport-of-water-and-solutes-in-plants
Used in: Lesson 6
Clark, M. A., Douglas, M., and Choi, J. Biology 2e. OpenStax, 2018. Section 2.2, Water (pH scale); section 5.2, Passive Transport (osmosis).
Nelson, M., G. Langellotto, and L. Nackley. Hydro hints: What is hydroponics? EM 9453. Oregon State University Extension Service, 2025.
https://extension.oregonstate.edu/catalog/em-9453-hydro-hints-what-hydroponics
Used in: Lesson 7
Nelson, M., II, G. Langellotto, and L. Nackley. Hydro hints: Nutrient film technique. EM 9457. Oregon State University Extension Service, 2025.
https://extension.oregonstate.edu/catalog/pub/em-9457-hydro-hints-nutrient-film-technique
Used in: Lesson 8
Nelson, M., II, G. Langellotto, and L. Nackley. Hydro hints: Ebb and flow. EM 9458. Oregon State University Extension Service, 2025.
https://extension.oregonstate.edu/catalog/pub/em9458
Used in: Lesson 8
MacSwan, I. C. Blossom-end Rot of Tomatoes. FS 139. Oregon State University Extension Service, revised March 2024.
https://extension.oregonstate.edu/sites/default/files/catalog/auto/FS139.pdf
Used in: Lesson 20
Dunn, B. Hydroponics. Fact sheet HLA-6442. Oklahoma State University Extension, 2025.
Singh, H., and B. Dunn. Electrical Conductivity and pH Guide for Hydroponics. Fact sheet HLA-6722. Oklahoma State University Extension, 2017.
https://extension.okstate.edu/fact-sheets/electrical-conductivity-and-ph-guide-for-hydroponics
Nelson, M., G. Langellotto, and L. Nackley. Hydro Hints: Deep Water Culture. EM 9455. Oregon State University Extension Service, 2025.
https://extension.oregonstate.edu/catalog/pub/em-9455-hydro-hints-deep-water-culture
Jones, G. B., S. Goode, and R. Simes. Soil: The Dirty Secrets of a Living Landscape. EM 9304. Oregon State University Extension Service, 2020.
https://extension.oregonstate.edu/catalog/pub/em-9304-soil-dirty-secrets-living-landscape
Used in: Lesson 2
VanDerZanden, A. M. Vegetative Plant Parts. EM 9904. Oregon State University Extension Service, 2008 (reviewed 2024).
Rofiansyah, W., Zalianty, F. R., La Ito, F. A., Wijayanto, I., Ryanu, H. H., and Irawati, I. D. IoT-based control and monitoring system for hydroponic plant growth using image processing and mobile applications. PeerJ Computer Science, 2025. doi:10.7717/peerj-cs.2763.
https://pmc.ncbi.nlm.nih.gov/articles/PMC12190697/
Used in: Lesson 26
Pennisi, G., Gianquinto, G., Marcelis, L. F. M., Martin, M., and Orsini, F. Vertical farming: productivity, environmental impact, and resource use. A review. Agronomy for Sustainable Development 45: 57, 2025. doi:10.1007/s13593-025-01055-w.
https://cris.unibo.it/retrieve/920146e0-8500-4c53-a465-98bb62c27d86/Pennisi%20et%20al%202025.pdf
Lee, J.-Y., Rahman, A., Azam, H., Kim, H. S., and Kwon, M. J. Characterizing nutrient uptake kinetics for efficient crop production during Solanum lycopersicum var. cerasiforme Alef. growth in a closed indoor hydroponic system. PLoS ONE 12(5): e0177041, 2017.
https://pmc.ncbi.nlm.nih.gov/articles/PMC5423622/
Used in: Lesson 11
Lehigh County Master Gardeners. Cool-season vs. Warm-season Vegetables. Penn State Extension, 2024.
https://extension.psu.edu/cool-season-vs-warm-season-vegetables
Used in: Lesson 1
Sánchez, E., F. Di Gioia, R. Berghage, N. Flax, and T. Ford. Hydroponics Systems and Principles of Plant Nutrition: Essential Nutrients, Function, Deficiency, and Excess. Penn State Extension, 2026.
Sánchez, E., and F. Di Gioia. Hydroponics Systems: Using the Two Basic Equations to Calculate a Nutrient Solution Recipe. Penn State Extension, 2026.
Used in: Lesson 9
Sánchez, E., and F. Di Gioia. Hydroponics Systems: Nutrient Solution Programs and Recipes. Penn State Extension, updated 2024.
https://extension.psu.edu/hydroponics-systems-nutrient-solution-programs-and-recipes
Used in: Lesson 4
Turfgrass Fertilization: A Basic Guide for Professional Turfgrass Managers. Penn State Extension, updated 2016.
https://extension.psu.edu/turfgrass-fertilization-a-basic-guide-for-professional-turfgrass-managers
Used in: Lesson 4
Boser, S., and Rizzo, D. A Water Quality Toolkit for Greenhouse and Nursery Production. Penn State Extension.
https://extension.psu.edu/a-water-quality-toolkit-for-greenhouse-and-nursery-production
Used in: Lesson 11
National Center for Biotechnology Information. Calcium nitrate (CID 24963), GHS classification. PubChem, National Library of Medicine.
https://pubchem.ncbi.nlm.nih.gov/compound/Calcium-nitrate
Used in: Lesson 9
Miller, A., Langenhoven, P., and Nemali, K. Optimal Fertilizer Solution Concentration for Hydroponic Lettuce Production. HO-309-W. Purdue Extension.
https://www.extension.purdue.edu/extmedia/HO/HO-309-W.pdf
Used in: Lesson 11
Torres, A. P., and R. G. Lopez. Measuring Daily Light Integral in a Greenhouse. HO-238-W. Purdue Extension.
https://www.extension.purdue.edu/extmedia/ho/ho-238-w.pdf
Used in: Lesson 5
Camberato, D. M., Lopez, R. G., and Mickelbart, M. V. pH and Electrical Conductivity Measurements in Soilless Substrates. HO-237-W. Purdue Extension.
https://www.extension.purdue.edu/extmedia/ho/ho-237-w.pdf
Used in: Lesson 10
Nemali, K. Looking through the pores of a soilless substrate. Controlled Environment Agriculture (Nemali Lab), Department of Horticulture and Landscape Architecture, Purdue University, 2017.
https://www.purdue.edu/hla/sites/cea/article/looking-through-the-pores-of-a-soilless-substrate/
Used in: Lesson 13
Royal Horticultural Society. Leaf damage on houseplants. RHS Advice.
https://www.rhs.org.uk/prevention-protection/leaf-damage-on-houseplants
Used in: Lesson 14
Sabeh, N. C., Giacomelli, G. A., and Kubota, C. Water use for pad and fan evaporative cooling of a greenhouse in a semi-arid climate. Acta Horticulturae 719: 409-416. International Society for Horticultural Science, 2006.
Used in: Lesson 25
City of Sioux Falls Water Purification Plant. Chloramines and Fish.
Used in: Lesson 17
Masser, M. P., Rakocy, J., and Losordo, T. M. Recirculating Aquaculture Tank Production Systems: Management of Recirculating Systems. SRAC Publication No. 452, March 1999 Revision. Southern Regional Aquaculture Center.
Used in: Lesson 26
Rakocy, J. E., Masser, M. P., and Losordo, T. M. Recirculating Aquaculture Tank Production Systems: Aquaponics, Integrating Fish and Plant Culture. SRAC Publication No. 454. Southern Regional Aquaculture Center; Oklahoma Cooperative Extension Service.
https://pods.okstate.edu/fact-sheets/SRAC-454pod.pdf
Used in: Lesson 20, Lesson 21, Lesson 22, Lesson 23, Lesson 24, Lesson 25
Mullins, C., Nerrie, B., and Sink, T. D. Principles of Small-Scale Aquaponics. SRAC Publication No. 5007. Southern Regional Aquaculture Center, September 2015.
https://srac.msstate.edu/pdfs/Fact%20Sheets/5007%20Principles%20of%20Small-Scale%20Aquaponics.pdf
Recsetar, M., and Kelly, A. Building a Simple At-home Aquaponics System. SRAC Publication No. 5010. Southern Regional Aquaculture Center, August 2016.
https://srac.msstate.edu/pdfs/Fact%20Sheets/5010.pdf
Used in: Lesson 23
Rakocy, J. E., Masser, M. P. and Losordo, T. M. Recirculating Aquaculture Tank Production Systems: Aquaponics, Integrating Fish and Plant Culture. SRAC Publication No. 454. Southern Regional Aquaculture Center, November 2006 revision.
Hargreaves, J. A. and Tucker, C. S. Managing Ammonia in Fish Ponds. SRAC Publication No. 4603. Southern Regional Aquaculture Center, December 2004.
https://www.srac.msstate.edu/pdfs/Fact%20Sheets/4603%20Managing%20Ammonia%20in%20Fish%20Ponds.pdf
Durborow, R. M., Crosby, D. M. and Brunson, M. W. Nitrite in Fish Ponds. SRAC Publication No. 462. Southern Regional Aquaculture Center, June 1997 (revised).
https://www.srac.msstate.edu/pdfs/Fact%20Sheets/462%20Nitrite%20in%20Fish%20Ponds.pdf
Used in: Lesson 18
Tucker, C. Pond Aeration. SRAC Publication No. 3700. Southern Regional Aquaculture Center, 2005.
https://uapb.edu/wp-content/uploads/2023/07/SRAC-3700-Pond-Aeration.pdf
Used in: Lesson 12
Sutton, J. C., et al. Etiology and epidemiology of Pythium root rot in hydroponic crops. Summa Phytopathologica 32(4): 307-321, 2006.
https://www.alice.cnptia.embrapa.br/alice/bitstream/doc/576855/1/a01v32n4.pdf
Used in: Lesson 12
Canelon, D. An introduction to hydroponics. University of Alaska Fairbanks Cooperative Extension Service, 13 December 2022.
https://ces.open.uaf.edu/2022/12/13/an-introduction-to-hydroponics/
Used in: Lesson 24
University of Arkansas at Pine Bluff, Department of Aquaculture and Fisheries. Aeration.
https://uapb.edu/academics/safhs/department-of-aquaculture-fisheries/pond-management/aeration/
Used in: Lesson 12
Liu, G., E. H. Simonne, and Y. Li. Nickel Nutrition in Plants. HS1191. University of Florida IFAS Extension.
https://ask.ifas.ufl.edu/publication/HS1191
Used in: Lesson 1
Watson, J. A., Gomez, C., Buffington, D. E., Bucklin, R., Henley, R. W., and McConnell, D. Greenhouse Ventilation. AE-10/AE030. UF/IFAS Extension, University of Florida.
https://ask.ifas.ufl.edu/publication/AE030
Used in: Lesson 25
Leary, J., Watson, J. A., Gomez, C., Bucklin, R., and McConnell, D. Fan and Pad Greenhouse Evaporative Cooling Systems. CIR1135/AE069. UF/IFAS Extension, University of Florida.
https://ask.ifas.ufl.edu/publication/AE069
Used in: Lesson 25
Francis-Floyd, R., Watson, C., Petty, D., and Pouder, D. B. Ammonia in Aquatic Systems. FA16. UF/IFAS Extension, University of Florida.
Hochmuth, G. J. Production Systems. Florida Greenhouse Vegetable Production Handbook, Vol 2. CV255. UF/IFAS Extension.
Eason, H. 'Set It and Forget It' Hydroponic Lettuce. HS1488. UF/IFAS Extension.
McGee, M. and Cichra, C. Principles of Water Recirculation and Filtration in Aquaculture. FA-12. Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published October 1988, reviewed April 2000.
University of Florida. Agricultural and Biological Engineering course descriptions (ABE 4320, ABE 4231C). University of Florida Catalog.
https://catalog.ufl.edu/UGRD/courses/agricultural_and_biological_engineering/
Used in: Lesson 26
Pinkerton, M. G., B. Whitman, H. Eason, and C. Gómez. Common Media Used in Hydroponics. ENH1359/EP623. UF/IFAS Extension, University of Florida.
https://ask.ifas.ufl.edu/publication/EP623
Used in: Lesson 13
Hochmuth, G., and Hochmuth, R. Fertilizer Management for Greenhouse Vegetables. Florida Greenhouse Vegetable Production Handbook, Vol. 3. CV265. UF/IFAS Extension.
https://ask.ifas.ufl.edu/publication/CV265
Used in: Lesson 11
Vought, K., Bayabil, H., and Martin-Ryals, A. How Efficient Are Hydroponic Lettuce Production Systems in Nutrient Usage Under Low and High Salinity? AE610. UF/IFAS Extension.
https://ask.ifas.ufl.edu/publication/AE610
Used in: Lesson 11
Pennisi, B. V. Growing Indoor Plants with Success. Bulletin 1318. University of Georgia Cooperative Extension, 2022.
https://fieldreport.caes.uga.edu/publications/B1318/growing-indoor-plants-with-success
Used in: Lesson 5
Westerfield, B., and M. English. Nutritional Deficiencies in Vegetables. Bulletin 1569. University of Georgia Cooperative Extension, 2024.
https://fieldreport.caes.uga.edu/publications/B1569/
Used in: Lesson 4
Sonon, L. S., Saha, U., and Kissel, D. E. Soil Salinity: Testing, Data Interpretation and Recommendations. Circular 1019. University of Georgia Cooperative Extension.
https://fieldreport.caes.uga.edu/wp-content/uploads/2025/08/C-1019_4.pdf
Used in: Lesson 11
Kaiser, C., and M. Ernst. Hydroponic Lettuce. CCD-CP-63. Center for Crop Diversification, University of Kentucky College of Agriculture, Food and Environment, 2016.
https://publications.ca.uky.edu/sites/publications.ca.uky.edu/files/hydrolettuce.pdf
Sharma, A., K. Leonberger, N. Gauthier, and Q. Ying. Hydroponic Lettuce Production in Controlled Environments. CCD-CP-63. Center for Crop Diversification, University of Kentucky, 2025.
https://ccd.uky.edu/sites/default/files/2026-02/ccd-cp-63_hydrolettuce-updated_accessible.pdf
University of Kentucky Cooperative Extension. Lettuce Diseases in Kentucky. PPFS-VG-53.
https://plantpathology.mgcafe.uky.edu/sites/plantpathology.ca.uky.edu/files/PPFS-VG-53.pdf
Used in: Lesson 12
Byrd, C., A. Sharma, and Q. Ying. Selecting Growing Media for Soilless Systems. CCD-TA-02. Center for Crop Diversification, University of Kentucky, 2025.
Used in: Lesson 13
Center for Agriculture, Food, and the Environment. Extension Outreach Overview. University of Massachusetts Amherst.
https://www.umass.edu/agriculture-food-environment/extension-outreach-overview
Used in: Lesson 26
Bartok, J. W., Jr. Shade for Cooling Greenhouses. UMass Extension Greenhouse Crops and Floriculture Program, University of Massachusetts Amherst, 2013.
Used in: Lesson 25
Lazur, A. Basics of Pond Aeration. University of Maryland Extension.
https://extension.umd.edu/sites/extension.umd.edu/files/2021-07/Basics%20of%20Pond%20Aeration.pdf
Used in: Lesson 12
Little, N. Chapter 1: Urban production systems. University of Maryland Extension, updated 3 March 2023.
https://extension.umd.edu/resource/chapter-1-urban-production-systems
Used in: Lesson 25
University of Maryland Extension. Yellowing Leaves on Vegetable Plants.
https://extension.umd.edu/resource/yellowing-leaves-vegetable-plants
Not used by a published lesson yet.
Schuh, M., and J. MacKenzie. Growing lettuce, endive and radicchio in home gardens. University of Minnesota Extension (reviewed 2024).
https://extension.umn.edu/vegetables/growing-lettuce-endive-and-radicchio
Used in: Lesson 5
Weisenhorn, J., and N. Hoidal. Lighting for indoor plants and starting seeds. University of Minnesota Extension (reviewed 2026).
https://extension.umn.edu/planting-and-growing-guides/lighting-indoor-plants
Used in: Lesson 5
Hoidal, N., Reardon, A., Worth, L., and Rogers, M. Small-scale hydroponics. University of Minnesota Extension.
Starting seeds indoors. University of Minnesota Extension, reviewed 2026.
https://extension.umn.edu/planting-and-growing-guides/starting-seeds-indoors
Not used by a published lesson yet.
UN News. UN sounds alarm over rising demands on water resources as scarcity increases. United Nations, 12 December 2025. Reports FAO's 2025 AQUASTAT Water Data Snapshot.
https://news.un.org/en/story/2025/12/1166582
Used in: Lesson 24
Supplemental Lighting Run Time Worksheet. University of New Hampshire Extension.
https://extension.unh.edu/resource/supplemental-lighting-run-time-worksheet
Used in: Lesson 5
Baxendale, F. P., S. N. Wegulo, D. E. Lott, and D. T. Lindgren. Guide to Growing Houseplants. NebGuide G2205. University of Nebraska-Lincoln Extension, 2013.
https://extensionpubs.unl.edu/publication/g2205/pdf/view
Used in: Lesson 14
Kranz, B. Irrigation Chapter 8: Irrigation Efficiencies. Irrigation Home Study Course, Plant and Soil Sciences eLibrary, University of Nebraska-Lincoln Extension.
https://passel2.unl.edu/view/lesson/bda727eb8a5a/8
Used in: Lesson 24
Transpiration - Water Movement through Plants: Major Plant Highlights. Plant and Soil Sciences eLibrary (PASSel).
https://passel2.unl.edu/view/lesson/c242ac4fbaaf/5
Used in: Lesson 6
Transpiration - Water Movement through Plants: Introduction. Plant and Soil Sciences eLibrary (PASSel).
https://passel2.unl.edu/view/lesson/c242ac4fbaaf/2
Used in: Lesson 6
Treftz, C., Kratsch, H., and Omaye, S. Hydroponics: A Brief Guide to Growing Food Without Soil. FS-15-08. Extension, University of Nevada, Reno, 2015.
https://naes.unr.edu/publication.aspx?PubID=2756
Used in: Lesson 24
Hitaj, C. Energy consumption in agriculture increased in 2016, driven mainly by diesel and fertilizer use. Charts of Note. USDA Economic Research Service, 13 March 2018.
https://www.ers.usda.gov/data-products/charts-of-note/87964
Used in: Lesson 24
Suttles, S. Farms spend more on indirect energy inputs like fertilizer than direct energy inputs like fuel. Charts of Note. USDA Economic Research Service, 12 February 2015.
https://www.ers.usda.gov/data-products/charts-of-note/77995
Used in: Lesson 24
USDA National Agricultural Library. Urban Agriculture.
https://www.nal.usda.gov/farms-and-agricultural-production-systems/urban-agriculture
Used in: Lesson 25
National Invasive Species Information Center, U.S. Department of Agriculture. What are Invasive Species?
https://www.invasivespeciesinfo.gov/what-are-invasive-species
Used in: Lesson 20
U.S. Fish and Wildlife Service, La Crosse Fish Health Center. Fish Surrender Program.
https://www.fws.gov/project/fish-surrender-program
Used in: Lesson 20
U.S. Fish and Wildlife Service. Understanding Injurious Wildlife Regulations.
https://www.fws.gov/story/understanding-injurious-wildlife-regulations
Used in: Lesson 20
U.S. Geological Survey. Celery draws up water from the roots into the top of the stalks. USGS Water Science School image, credit K. Doyle.
https://www.usgs.gov/media/images/celery-draws-water-roots-top-stalks
Used in: Lesson 6
U.S. Geological Survey. Deserts. Land Management Research Program.
https://www.usgs.gov/programs/land-management-research-program/deserts
Used in: Lesson 25
U.S. Geological Survey, Water Science School. Dissolved Oxygen and Water.
https://www.usgs.gov/special-topics/water-science-school/science/dissolved-oxygen-and-water
U.S. Geological Survey. Chapter A6.2, Dissolved Oxygen. Techniques and Methods 9-A6.2, 2020. Table 6.2-2, oxygen solubility in fresh water.
https://pubs.usgs.gov/tm/09/a6.2/tm9a6.2.pdf
Used in: Lesson 12
U.S. Geological Survey. Evapotranspiration and the Water Cycle. USGS Water Science School, 2018.
https://www.usgs.gov/special-topics/water-science-school/science/evapotranspiration-and-water-cycle
Used in: Lesson 6
McCoy, G. A. Water quality: Briefing paper on periphyton. Quality of Water Branch Technical Memorandum No. 78.10. U.S. Geological Survey, Water Resources Division, June 22, 1978.
https://water.usgs.gov/admin/memo/historical/qw78.10Historical.txt
Used in: Lesson 17
U.S. Geological Survey, Water Science School. pH and Water.
https://www.usgs.gov/special-topics/water-science-school/science/ph-and-water
Used in: Lesson 10
U.S. Geological Survey. Runoff: Surface and Overland Water Runoff. USGS Water Science School.
Used in: Lesson 24
U.S. Geological Survey. Water, the Universal Solvent. USGS Water Science School.
https://www.usgs.gov/special-topics/water-science-school/science/water-universal-solvent
Used in: Lesson 2
USU Extension. The Purpose and Benefit of Land-grant (Extension) Universities. Utah State University, 14 February 2022.
https://extension.usu.edu/news/purpose-and-benefit-of-land-grant-extension-universities
Used in: Lesson 26
Spangenberg, B. Understanding Soil P & K. Wisconsin Horticulture, University of Wisconsin-Madison Division of Extension.
https://hort.extension.wisc.edu/understanding-soil-p-k/
Used in: Lesson 4
Let's Experiment with Plant Plumbing. Washington State University and Master Gardener Foundation of King County.
Used in: Lesson 6
Common Cultural: Fertilizer burn. Hortsense, Washington State University Extension.
https://hortsense.cahnrs.wsu.edu/fact-sheet/common-cultural-fertilizer-burn/
Used in: Lesson 14
Cogger, C. A Home Gardener's Guide to Soils and Fertilizers. EM063E. Washington State University Extension, 2014 (revised 2020).
Koenig, R. T., and Koenig, T. C. Chapter 4: Plant Mineral Nutrition and Fertilizers. In The Pacific Northwest Gardener's Handbook. Washington State University Extension.
https://extension.wsu.edu/pnw-gardeners-handbook/chapter-4-plant-mineral-nutrition-and-fertilizers/
Used in: Lesson 10
Pan, B. Nutrient Movement Towards and Into Plant Roots. Soils 441, Unit 1, Lesson 4. Washington State University.
https://apps.aoi.wsu.edu/onlineMedia/pdf_version/soils441_08_art(c123).pdf
Used in: Lesson 3
Accessible Gardening: Hydroponic Gardening. Green Thumbs, Healthy Joints, West Virginia University, 2011.
https://greenthumbs.cedwvu.org/media/1166/hydroponicgardening.pdf
Used in: Lesson 7