Library on PonicLabs

What a plant needs: the seven inputs

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to list the seven inputs a plant needs to grow, say what each one does inside the plant, and explain why a plant grown without soil is not missing anything. You will also be able to estimate how many litres of water a head of lettuce moves through itself before harvest.

Photosynthesis and respiration for growers

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to say where the mass of a plant comes from, read a light-response curve and name the three environmental factors that cap photosynthesis, turn a light-meter reading and a photoperiod into a daily light integral and compare it with a published lettuce target, and explain why roots in a nutrient solution need dissolved oxygen and why warm nights cost growth.

Water in the plant: uptake, transpiration and humidity

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to describe how water travels from the nutrient solution to the air through root, xylem and stomata, explain why that stream carries nutrients and why calcium depends on it, and calculate the vapour-pressure deficit of the air from a temperature and a relative humidity.

Before you read: What a plant needs, Photosynthesis and respiration for growers.

What plants are made of: the essential elements

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to name the chemical elements a plant cannot complete its life without, explain the test that puts an element on that list, read a table of typical tissue concentrations, and estimate how many grams of nitrogen and potassium a head of lettuce contains. You will also know why a shortage of some elements shows first on old leaves and a shortage of others on young ones.

How roots take up nutrients

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to explain what a root actually absorbs, how each ion reaches the root surface and crosses the root’s membrane, why that needs oxygen, why solution and plant end up with different compositions, and why nitrate feeding pushes pH one way and ammonium feeding the other. A worked example turns one head of lettuce into millimoles of charge.

Water quality: what is in your water and why it matters

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to read a water report line by line, sort each constituent into useful, harmless up to a limit, or a cause of trouble, compare tap, rain, reverse-osmosis and well water, and decide with published limits whether a given water suits lettuce and how much calcium and magnesium it already brings to your recipe.

pH: what it is and why 5.5 to 6.5

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to say what a pH reading measures and why one unit is a tenfold step, explain from solution chemistry why hydroponic growers keep the solution slightly acid, predict which way a running system will drift, calibrate and store a pH electrode, and correct pH without overshooting, dosing by the water’s alkalinity rather than by the pH reading alone.

Alkalinity and buffering: the hidden control of pH drift

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to tell alkalinity apart from pH, convert between the units in which laboratories report it, explain from the carbonate equilibrium why a running system drifts upwards in pH, and calculate how many millilitres of nitric or phosphoric acid a tank needs and how much nitrogen or phosphorus that dose adds to the recipe.

EC and concentration: what the meter measures

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to read an EC meter in any of the units it may show, convert a reading between mS/cm, dS/m, µS/cm, CF and the ppm scales, correct a reading taken at the wrong temperature, estimate the EC of a simple recipe from its ion concentrations, and say what an EC reading can and cannot tell you about a nutrient solution.

Fertiliser salts: purity, solubility and compatibility

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to name the salt that supplies each element of a nutrient solution, calculate the element content of a salt from its formula and check it against the bag label, read a purity grade, use a solubility limit to size a stock tank, and explain from the chemistry why calcium nitrate is never concentrated together with sulfates or phosphates.

Reading a formulation: Hoagland, Steiner and modern recipes

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to convert any nutrient recipe between milligrams per litre and millimoles per litre, check that its positive and negative charges balance, translate a fertiliser label written in P₂O₅ and K₂O, and put the classic Hoagland and Steiner solutions beside a modern commercial recipe and say what the differences mean.

Mixing your own solution: from a recipe to grams on the scale

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to turn a recipe in milligrams of each element per litre into grams of each fertiliser salt for your tank, correcting for your raw water and for the purity on the bag. You will know in which order to solve the elements, how to make A and B stocks that do not precipitate, how to dissolve the salts, and what the EC meter should read when you are done.

Managing a recirculating solution over time

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to explain why a recirculating solution never stays as you mixed it, read EC and pH drift as evidence of what the crop and the make-up water are doing, write a one-line mass balance for sodium, calculate how many weeks a given water takes to push sodium past a limit, and choose between topping up, bleeding and replacing on evidence rather than on the calendar.

Dissolved oxygen in the root zone

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to read an oxygen solubility table, convert between mg/L, µmol/L and percent saturation, estimate how long the oxygen in a tank would last against a measured root respiration rate, explain what an air stone and water flow actually do, and compare your meter reading with the concentrations at which lettuce grows well and suffers.

Anatomy of a hydroponic system: the design parameters

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to look at any hydroponic system, from a bottle on a windowsill to a commercial greenhouse, and say what it does for the roots, where it sits on four design axes, how much solution it holds per plant, and what will go wrong first. You will also be able to estimate how much water a small lettuce crop drinks and compare that with the buffer each kind of system gives you.

Kratky and other passive systems: growing with an air gap and no pump

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to explain how a plant in a lidded container of nutrient solution gets its oxygen when nothing stirs or bubbles the water, size a container for a lettuce crop from published consumption figures, and say which crops the method suits and why. You will also know the main ways a passive system fails and the mechanism behind each.

Deep water culture: roots in a deep, aerated solution

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to explain how deep water culture keeps roots alive in a tank of solution, why its volume makes it forgiving, why the air pump can never stop, and how commercial raft ponds are laid out. You will also be able to size the solution volume, the oxygen store and the air flow for a square metre of lettuce with a calculator.

Nutrient film technique: growing roots in a moving film

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to explain why a nutrient film technique (NFT) channel only works while the film of solution stays a few millimetres deep, choose a slope, a flow rate and a channel length from that mechanism, size the catchment tank and pump for a stated number of plants, and recognise the three ways an NFT system fails.

Drip irrigation and substrate culture: slabs, bags and Dutch buckets

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to explain why a crop in a rockwool, coir or perlite substrate is watered many times a day in small doses, choose between draining the surplus to waste and recirculating it, set a drain fraction and read the drain EC, and size the daily irrigation of a tomato crop from its transpiration and its slab.

Growing media I: air, water and particle size

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to describe a growing medium as solid, water and air sharing one volume, define total porosity, container capacity, air-filled porosity and bulk density, read a water-retention curve, and explain why the bottom of a drained container is always saturated. You will also be able to estimate how much air a slab or a pot of a given height holds.

Choosing a medium: stone wool, coir, perlite, expanded clay, peat and others

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to compare the growing media sold for hydroponics on measured properties rather than on claims, say which property makes a medium suit a net pot, a propagation block, a drip slab, a bucket or a wick system, prepare stone wool and coir before planting, and work out how much medium a set of containers needs.

Light: PPFD, DLI, spectrum and photoperiod

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to explain why plant light is counted in photons, turn a light reading and a day length into a daily light integral and back, compare it with targets for lettuce, basil and seedlings, and estimate the dry matter it can buy. You will also know what each colour of light does, and when long days help or harm a crop.

Choosing and sizing grow lights

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to compare grow lights by the one number that matters for plants, photons per joule of electricity, and to work out how many watts a shelf or room needs for a chosen light level. You will also be able to estimate the daily electricity cost, the heat the lamp adds to the room, and whether a dearer, more efficient fixture pays for itself.

Temperature, humidity and VPD

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to explain why each plant process has a minimum, an optimum and a maximum temperature, set day and night temperatures for lettuce, basil and fruiting crops from sourced ranges, and use the daily mean temperature to predict timing. You will also be able to read a VPD table, compute a dew point, and decide whether a grow room will drip at night.

Seeds, germination and propagation

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to sow seeds in plugs at the right temperature, light and moisture, recognise and prevent damping-off, and decide when a seedling is ready for its hydroponic system. You will also be able to test a seed packet, calculate how many seeds to sow for the plants you want, and root basil from cuttings.

How long things take: growth timelines for eleven crops

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to read a published crop timeline and say what it actually measured, find a sourced range from sowing to harvest for eleven common hydroponic crops, and turn a timeline into a weekly sowing plan that gives a steady harvest. You will also know what to record so that your own notes become a better guide for your system than any published table.

Growing leafy greens and herbs: lettuce, basil, spinach and others

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to run lettuce, basil and spinach from transplant to harvest in any common hydroponic system, with a sourced range for solution strength, pH, temperature, light and spacing. You will know why lettuce leaves burn at the edges, why crops run to seed, why basil blackens in the cold, and what one square metre of lettuce can yield in a year.

Diagnosing nutrient deficiencies and toxicities

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to look at a plant with yellow, brown or deformed leaves and narrow the cause to one or two elements by asking which leaves show it first and what the pattern is. You will then know how to confirm the diagnosis with a solution test, a tissue analysis and a corrective dose, and why in hydroponics the solution is often not short of the element at all.

Pests and diseases in soilless systems

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to explain why a shared nutrient solution makes root diseases spread faster than in soil, tell a rotting root from a healthy one, and match the common leaf diseases and insect pests to the conditions that favour them. You will also be able to set up a weekly sticky-card count for a small grow room and work out how much hydrogen peroxide a tank needs for a published treatment dose.

Water, energy and nutrients: what the evidence says

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will know which study the “90% less water” claim comes from and what that study compared. You will be able to estimate the water a kilogram of lettuce must transpire and the electricity an indoor farm needs to light it, and you will know why the climate footprint of hydroponic food depends more on the power grid than on the growing method.

Meters and measurement: pH, EC, dissolved oxygen and temperature

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will know what each of your meters actually senses, how to calibrate a pH meter and judge from its slope whether the electrode is worn out, how to correct an EC reading to 25 °C, and how to choose an oxygen sensor. You will also know how large a meter’s error is compared with your targets.

Build: a single-container Kratky system

Tue, 20 Oct 2026 00:00:00 +0200

Standfirst: After reading this article you will be able to build a Kratky container for one lettuce from a parts list, fill it to the right level, mix the solution by weight, and run the crop to harvest without a pump. You will also be able to size the same build as a tote for four to six plants, and to read the common failures from their symptoms.

Part A. Foundations: what a plant needs and how it works

Mon, 01 Jan 0001 00:00:00 +0000

Part B. The nutrient solution

Mon, 01 Jan 0001 00:00:00 +0000

Part C. Systems and media

Mon, 01 Jan 0001 00:00:00 +0000

Part D. Environment

Mon, 01 Jan 0001 00:00:00 +0000

Part E. Crops and practice

Mon, 01 Jan 0001 00:00:00 +0000

Part F. Measuring, building and scaling

Mon, 01 Jan 0001 00:00:00 +0000