Reference

The growing glossary

Plain definitions of the terms that come up most in organic growing, and across the Dr Forest range.

No jargon for its own sake. Where a term has a fuller guide, there is a link to it.

Amino acids (protein hydrolysate)

Pre-assembled building blocks of protein that a plant can absorb and use directly, saving the energy of making them itself. Gently, enzymatically split products keep more of the useful L-form amino acids than harsher chemical ones.

See: Amino acid biostimulants

Base saturation

The proportion of a soil's cation exchange capacity occupied by base cations: calcium, magnesium, potassium and sodium. The Base Cation Saturation Ratio theory tries to fix the ratios between them; sufficiency, the approach Dr Forest follows, does not.

Biochar

Charcoal made specifically for soil, not the barbecue. It is porous and long-lasting, improving structure and helping the soil hold nutrients and water. On already fertile UK soil its yield effect is modest; its value is structural and long-term.

Biostimulant

A material that improves how a plant grows, or how it copes with stress, without supplying a meaningful amount of nutrients. Seaweed, fulvic acid and amino acids are biostimulants: their value is in their bioactive compounds, not their NPK.

Blossom end rot

A sunken brown patch at the base of tomatoes and peppers, caused by calcium failing to reach the developing fruit. It is usually a watering and transpiration problem rather than a shortage of calcium in the soil, so more feed rarely fixes it.

Bokashi (EM-1)

A method of fermenting food waste in a sealed bucket using EM-1, a mixed culture of beneficial microbes such as lactic-acid bacteria and yeasts. It pickles waste, including cooked food and dairy, that an open compost heap cannot handle.

See: Bokashi bran

Brix

A measure of the dissolved solids, mostly sugars, in plant sap, read with a refractometer. It is often used as a rough proxy for flavour and plant health, though many factors affect the reading and it is not a single measure of quality.

Cation exchange capacity (CEC)

A measure of how much a soil can hold on to positively charged nutrients, such as potassium, calcium, magnesium and ammonium, against being washed out. Clay and organic matter raise it; sandy soils are low.

Chelation

Wrapping a metal micronutrient, such as iron, zinc or manganese, in an organic molecule that keeps it soluble and available to the plant rather than locked up by the soil. Fulvic acid is a natural chelator.

Chloride-free potash

A source of potassium that contains no chloride, such as sulphate of potash or polyhalite. Useful for chloride-sensitive crops and anywhere chloride build-up is a concern, unlike muriate of potash.

See: Polyhalite vs sulphate of potash

Chlorosis (interveinal)

Yellowing of leaves caused by too little chlorophyll, usually a nutrient problem. Interveinal chlorosis, where the veins stay green and the tissue between yellows, points to magnesium on older leaves or iron on the youngest.

See: Why tomato leaves turn yellow

Compost tea

A brew made by steeping compost in aerated water to multiply its microbes, then applied as a soil drench or foliar spray. Its quality depends heavily on the compost used and on proper aeration.

Cover crop (green manure)

A crop grown to protect and improve the soil rather than to harvest, then cut down or dug in. It shields bare ground, adds organic matter, and in the case of legumes fixes nitrogen.

Foliar feeding

Applying dilute nutrients or biostimulants directly to the leaves, where they are absorbed quickly. It is a useful top-up, especially for trace elements, but not a replacement for feeding the soil.

Fulvic acid

The smallest and most active fraction of the humic substances in healthy soil, and the part that actually gets inside the plant. It is a biostimulant rather than a feed: it keeps iron, zinc and manganese soluble and helps roots take up nutrients more efficiently.

See: What is fulvic acid

Hormesis

A dose effect where a small amount stimulates and a larger amount inhibits. It is why biostimulants such as fulvic acid have a sweet spot, and why more is not better; overdosing can set growth back.

See: How to apply fulvic acid

Humic acid

A larger humic fraction, usually extracted from leonardite, an ancient oxidised form of lignite. It improves soil structure and nutrient holding. Because it is mined from leonardite, it is not an organic input.

JADAM Microbial Solution (JMS)

A homemade microbial inoculant made by fermenting forest leaf mould with a boiled potato in salted water. A low-cost way to add a broad population of soil microbes.

See: How to make JMS

Leonardite

A soft, oxidised form of lignite, or brown coal, and the usual commercial source of humic and fulvic acids. Because it is mined, leonardite-derived products are not organic inputs.

Liebig's law of the minimum

The principle that growth is limited by the scarcest essential nutrient, not by the total amount of nutrients present. Adding more of a nutrient already in good supply will not help; only fixing the one in shortest supply does.

Loam (soil texture)

A balanced soil texture of sand, silt and clay that drains freely yet holds water and nutrients well. It is the texture most plants grow best in.

Macronutrients and micronutrients

Plants need seventeen essential nutrients. The macronutrients (nitrogen, phosphorus, potassium, calcium, magnesium, sulphur) are used in large amounts; the micronutrients (iron, manganese, zinc, copper, boron, molybdenum, chlorine, nickel) in traces. A shortage of any one limits growth, however much of the others is present.

See: What is a fertiliser

Micronised

Ground to a very fine particle size. Micronising a mineral increases its surface area, so it dissolves and becomes available to plants faster than a coarse grade.

Mycorrhizal fungi

Soil fungi that form a partnership with most plant roots, extending their reach for water and phosphorus in exchange for sugars. They help most garden plants but do nothing for brassicas, beetroot or rhododendrons.

See: Mycorrhizal fungi guide

No-dig

A way of growing that leaves the soil structure undisturbed, feeding from the surface with compost and mulch rather than digging or rotavating. It protects soil life, structure and stored carbon.

NPK

The three numbers on any fertiliser: nitrogen (N), phosphorus (P) and potassium (K), the nutrients plants use in the largest amounts. By UK convention, phosphorus and potassium are stated as their oxides, P₂O₅ and K₂O, not as the pure element.

Organic matter (soil)

Decomposed plant and animal material in the soil. It improves structure, water holding and cation exchange capacity, and feeds soil life. Most UK garden soils benefit from more of it.

Oxide form

The convention of expressing phosphorus, potassium, calcium, magnesium and sulphur as their oxides (P₂O₅, K₂O, CaO, MgO, SO₃), while nitrogen is given as the element. Dr Forest states nutrients this way so the numbers are directly comparable with other fertilisers.

Polyhalite

A naturally occurring mineral that supplies four nutrients at once: potassium, calcium, magnesium and sulphur, with no chloride. The Yorkshire polyhalite Dr Forest uses runs about 14% K₂O, 17% CaO, 6% MgO and 48% SO₃ (around 19% sulphur as the element).

See: What is polyhalite

Seaweed extract (Ascophyllum nodosum)

A biostimulant made from cold-water kelp. Its value is in natural plant hormones and other bioactive compounds, not its small NPK. The extraction method matters more than the figure on the label.

See: Seaweed fertiliser, explained

Slow-release fertiliser

A fertiliser that releases its nutrients gradually rather than all at once. Natural slow release comes from minerals and organic matter breaking down; it is worth avoiding polymer-coated products, which release on temperature and leave microplastic behind.

Soil pH

A measure of soil acidity or alkalinity that controls how available each nutrient is. Most UK garden plants do best around pH 6.0 to 6.5, and pH drifts over time even in well-tended soil.

See: How to change your soil pH

Sufficiency (vs BCSR / Albrecht)

The principle that a plant needs each nutrient above a minimum sufficiency level, and that adding more beyond that does not help. Dr Forest formulates to sufficiency rather than the Base Cation Saturation Ratio (the 'Albrecht' theory), which aims for fixed soil cation ratios and is not supported by field trials.

Sulphate of potash (SOP)

A concentrated, chloride-free source of potassium (potassium sulphate), about 50% K₂O, with sulphur. Useful where a crop needs potassium without the calcium and magnesium that polyhalite also brings.

See: Polyhalite vs sulphate of potash

Top dressing

Applying fertiliser to the soil surface around an established plant and letting watering and worms work it in. The simplest way to feed through the growing season.

See: How to top dress

Triacontanol

A natural plant growth regulator found in alfalfa, first identified in a 1977 paper in the journal Science. It is the reason alfalfa meal does more for a plant than its modest NPK suggests.

See: Alfalfa meal

Volcanic rock dust (basalt)

Finely ground volcanic rock that slowly releases silicon and a broad range of trace minerals as it weathers. On already fertile UK soil its yield effect is modest; its value is in remineralisation and soil structure over the long term.

See: Volcanic rock dust

Wetting agent (surfactant)

A material that lowers water's surface tension so it spreads and soaks into dry or water-repellent compost instead of running straight off. Natural options include the saponins in soap nuts.

See: What is a wetting agent

Can't find a term? Email joe@drforest.co.uk and it will be added.