What Is Hoagland’s Solution and How Do You Make It?

Hoagland’s solution is a plant food recipe dissolved in water, designed to give a plant every mineral it needs so it can grow with its roots in liquid instead of soil.1Wikipedia. Hoagland solution – Wikipedia That makes it a standard reference mix that labs, classrooms, and hydroponic growers can follow to get the same result anywhere. The recipe has been tweaked several times since the 1930s, so “Hoagland’s solution” really names a small family of closely related versions rather than one fixed formula.2Wikipedia. Hoagland solution – Wikipedia

Where Hoagland’s Solution Came From and Why It Is Still Used

Dennis Hoagland and Snyder published the first version in 1933, Hoagland and Arnon changed it in 1938, and Arnon revised it again in 1950.3Wikipedia. Hoagland solution – Wikipedia Most of the changes were made to keep iron dissolved where roots can reach it and to fine-tune the trace minerals.4Wikipedia. Hoagland solution – Wikipedia Plain iron tends to drop out of solution where roots can’t use it, which is why the recipe pairs it with EDTA, a chelator that holds iron dissolved.5Wikipedia. Hoagland solution – Wikipedia The 1938 versions trimmed the trace minerals down to the ones now accepted as essential: boron, manganese, zinc, copper, molybdenum, iron, and chlorine.6Wikipedia. Hoagland solution – Wikipedia

Scientists want a fully known plant food because soil varies from yard to yard, which makes results hard to compare or repeat. A recipe in water lets you know exactly what the plant received. You can also remove one ingredient to see what happens when a plant goes without it.

Its balance also holds up against other recipes. Across a dozen standard hydroponic recipes developed over more than 100 years, the ratios of potassium, magnesium, and calcium, and of nitrogen, sulfur, and phosphorus, stay remarkably similar.7Science in Hydroponics. Standard hydroponic formulations from the scientific literature Hoagland’s works for a large variety of plant species rather than one crop.8Wikipedia. Hoagland solution – Wikipedia

Many handouts say “Hoagland No. 1” or “No. 2,” the two 1938 recipes. No. 2 swaps part of the nitrate for an ammonium salt. If your instructions don’t specify, follow the ingredient table you were given exactly.

What Is in Hoagland’s Solution

The recipe is four major salts plus small amounts of trace minerals and protected iron. The nutrients plants need in large amounts come from the first four items below, and those needed in tiny amounts from the last two. Hoagland No. 1 per liter of finished solution:

The “·7H2O” in a name like magnesium sulfate heptahydrate means the salt crystal includes water, so weigh that exact form. A dry version of the same salt weighs differently. Epsom salt from a pharmacy is magnesium sulfate heptahydrate, but check that the bottle’s formula matches the recipe before you weigh. Trace-mineral amounts per liter are too tiny to weigh accurately, and too much boron or copper can harm plants, so trace minerals are mixed into a concentrated stock rather than weighed out for each liter.

Hoagland No. 2 uses more potassium nitrate (606.6 mg), less calcium nitrate (944.6 mg), and ammonium phosphate (115 mg) in place of monopotassium phosphate.15shop.gmexpression.com. Shop culture media and protein expression products! The trace minerals and iron stay the same, apart from a smaller molybdenum amount.16shop.gmexpression.com. Shop culture media and protein expression products!

The finished solution supplies about 210 ppm nitrogen, 235 ppm potassium, 200 ppm calcium, 64 ppm sulfur, 48.6 ppm magnesium, and 31 ppm phosphorus.17PubMed. Hoagland solution Later versions lowered calcium to about 160 ppm and raised iron from 1 ppm to as much as 5 ppm.18PubMed. Hoagland solution

How to Make Hoagland’s Solution Step by Step

The standard method makes several stock solutions, concentrated mixes you dilute later, in separate bottles before you ever make the plant solution.19protocols.io. Making Hoagland’s No. 1 Solution One common setup uses stock A with potassium, calcium, and nitrate; stock B with magnesium, ammonium, and phosphate; stock C with all the trace minerals; and stock D with iron.20PROMETHEUS. Hoagland’s nutrient solution These stocks cannot be mixed together while concentrated.21PROMETHEUS. Hoagland’s nutrient solution Calcium and phosphate meeting at high strength would form a solid that settles out.

You need a scale reading to at least 0.01 gram for the major salts, and separate labeled bottles, ideally glass, for each stock. A measuring cylinder or pipette handles the small stock volumes. Add a stirrer or clean spoon, plus gloves and eye protection.

Make each stock many times stronger than the final solution, for example strong enough that a few milliliters serves one liter. Multiply the per-liter amounts from the recipe by that factor, and write the dilution on each label so you never have to guess later.

To dissolve each stock, weigh the ingredients, fill your container to about 80 to 90 percent with distilled water, and stir until no residue remains.22PROMETHEUS. Hoagland’s nutrient solution Then top up to the exact final volume, such as 1 or 2 liters.23PROMETHEUS. Hoagland’s nutrient solution Add iron chelate powder slowly over a minute or two while stirring so clumps don’t form, then stir 5 to 15 minutes; heating shouldn’t be needed.24protocols.io. Making Hoagland’s No. 1 Solution Be extra careful measuring the tiny trace-mineral amounts.25PROMETHEUS. Hoagland’s nutrient solution Use a clean, dry spoon or weighing boat for each salt, and tare the scale with the boat on it so you weigh only the salt.

For 1 liter of working solution, put about 900 mL of water in a container first.26PROMETHEUS. Hoagland’s nutrient solution Add the set amount of each stock one by one, stirring between each, before topping up to 1 liter.27PROMETHEUS. Hoagland’s nutrient solution Adding each to a lot of water keeps calcium and phosphate dilute when they meet.28PROMETHEUS. Hoagland’s nutrient solution Measure the liquid stocks with a pipette, syringe, or small measuring cylinder, and rinse the tool between stocks so one doesn’t carry into the next. Read volumes at the bottom of the curve at eye level, since a few milliliters of error in a concentrated stock noticeably changes the final strength. Tap water is acceptable and cheap for the diluted solution, though distilled water keeps the recipe exact.29PROMETHEUS. Hoagland’s nutrient solution

Pouring stocks into each other instead of into water causes cloudiness. A white haze means calcium phosphate has formed and the batch is off. If the batch turns cloudy, remake it rather than use it.

Setting the Right pH

Fresh solution often starts acidic, around pH 4 to 5, because phosphate salts like monopotassium phosphate are acidic.30Science in Hydroponics. Standard hydroponic formulations from the scientific literature One lab protocol targets pH 5.5, give or take 0.1, and adjusts only if it’s off.31protocols.io. Making Hoagland’s Complete Nutrient Solution for Hydroponics You raise pH with dilute potassium hydroxide (0.1 M) and lower it with dilute sulfuric acid (0.2 M), a few drops at a time.32protocols.io. Making Hoagland’s Complete Nutrient Solution for Hydroponics

Check pH only after every stock has been added and the batch is topped up to its final volume, because each addition changes the reading. Let the solution stir for a few minutes before the first reading.

A calibrated pH meter is more accurate than paper strips. Calibrate it with standard buffer before each session, and after each drop of acid or base, stir and wait for the reading to settle.

pH matters because it controls how well minerals stay dissolved and available to roots.33Horticulturae. Precise Management of Hydroponic Nutrient Solution pH: The Effects of Minor pH Changes and MES Buffer Molarity on Lettuce Physiological Properties It changes during growing because plants take up some minerals faster than others.34Horticulturae. Precise Management of Hydroponic Nutrient Solution pH: The Effects of Minor pH Changes and MES Buffer Molarity on Lettuce Physiological Properties The balance of ammonium and nitrate in the recipe shifts whether the solution drifts acidic or basic.35Scientia Horticulturae. Solution Ammonium: Nitrate ratio and cation/anion uptake affect acidity or basicity with floriculture species in hydroponics So recheck a few days into growing, not just at mixing. In lettuce, adding a buffer called MES kept pH steady between 6.0 and 6.5 and raised yield by 17%.36Horticulturae. Precise Management of Hydroponic Nutrient Solution pH: The Effects of Minor pH Changes and MES Buffer Molarity on Lettuce Physiological Properties

Full Strength or Half Strength

For Arabidopsis, a small lab plant, half-strength Hoagland’s performed about the same as other specialized recipes.37PubMed Central. Nutrient solutions for Arabidopsis thaliana: a study on nutrient solution composition in hydroponics systems Bitter melon, though, grew bigger as solution strength increased, because a heavy-feeding plant uses the extra nutrients.38PubMed Central. Effect of Hoagland’s nutrient solution strengths and sodium silicate on growth, yield and biochemical parameters of Carla (Momordica Charantia L.) under hydroponic conditions So match strength to how hungry your plant is.

Seedlings and small plants usually start at half strength. Leafy fast growers and fruiting plants can use full strength. You make half strength simply by using half the stock volume per liter. Leaf burn at the edges can be a sign the solution is too strong.

EC, electrical conductivity, measures how much dissolved salt is in the water and is shown on cheap hydroponic meters.39Proc. Fla. State Hort. Soc.. Effects of Hoagland’s Solution Concentration and Aeration on Hydroponic Pteris vittata Production EC rises in a straight line as you make the solution stronger.40Proc. Fla. State Hort. Soc.. Effects of Hoagland’s Solution Concentration and Aeration on Hydroponic Pteris vittata Production It also creeps up over time as water evaporates and plants leave salts behind.41Proc. Fla. State Hort. Soc.. Effects of Hoagland’s Solution Concentration and Aeration on Hydroponic Pteris vittata Production

Keeping Roots Healthy While Using It

When root water lacks oxygen, roots switch to a low-energy mode and run short of fuel.42Scientia Horticulturae. Effects of oxygen concentration in solution and uptake rate by roots on cut roses yield, and nutrients and sugars content in leaves Uptake of phosphorus, magnesium, zinc, manganese, and especially potassium then drops.43Scientia Horticulturae. Effects of oxygen concentration in solution and uptake rate by roots on cut roses yield, and nutrients and sugars content in leaves Unaerated solution also tends to rise in pH because roots release less acid.44Scientia Horticulturae. Effects of oxygen concentration in solution and uptake rate by roots on cut roses yield, and nutrients and sugars content in leaves In still-water setups, an aquarium air pump and air stone fix this.

Healthy roots look white or cream and firm. Brown, slimy roots and a sour smell signal low oxygen. Plants may wilt even though they sit in water. If you see these signs, change the solution and add aeration.

Reading What Your Plants Tell You

Make one batch with all ingredients and others each missing one salt, then grow identical seedlings in each and compare after a few weeks. Substitute a salt that adds no new nutrient so only one thing changes, and photograph leaves to record symptoms.

Before blaming a missing nutrient, check pH first, because wrong pH locks out nutrients already present. Old solution can be depleted even if mixed correctly, and low oxygen mimics several deficiencies.

Storing Stocks and Disposing of Old Solution

Store all stock solutions in a refrigerator at about 4 °C until needed.52protocols.io. Making Hoagland’s No. 1 Solution Iron chelates break down in light, so keep the iron stock in an amber bottle or wrapped in foil.53protocols.io. Making Hoagland’s No. 1 Solution Label each bottle with the date made, and mix working solution fresh rather than storing it long. Cloudiness or settled crystals in a stock means you should remake it, and mold or a film suggests contamination.

Used nutrient solution is high in phosphorus, which can feed algae blooms in lakes and streams.54Resources, Conservation and Recycling Advances. A two-step approach to recycling hydroponics waste nutrient solutions using fertiliser drawn forward osmosis and chemical precipitation Dilute leftovers and use them to water garden or potted plants rather than pouring them into drains or storm gutters.

How It Compares With Garden and Organic Fertilizers

Lettuce grew more on Hoagland and Arnon solution than on a commercial organic fertilizer or none.55Journal of Plant Nutrition. Comparisons of commercial organic and chemical fertilizer solutions on growth and composition of lettuce Hoagland-grown lettuce had more nitrogen, potassium, magnesium, and iron, while organic-fed lettuce had more phosphorus.56Journal of Plant Nutrition. Comparisons of commercial organic and chemical fertilizer solutions on growth and composition of lettuce But Hoagland-fed leaves were high in nitrate, while organic or unfed lettuce stayed low.57Journal of Plant Nutrition. Comparisons of commercial organic and chemical fertilizer solutions on growth and composition of lettuce

Use Hoagland’s when you need a repeatable, known recipe, as in experiments. Premixed hydroponic fertilizers are easier for casual home growing, and organic feeds suit anyone who prioritizes lower leaf nitrate over yield. Never use Hoagland chemicals in soil gardens at random doses.