Fertiliser
Organic Tomato Fertiliser | Slow Release Tomato Feed 3-4-6
A slow-release 3-4-6 feed for tomatoes.
from £11.50
High-nitrogen certified organic fertiliser — 13% plant-based amino-acid nitrogen for strong, leafy growth
In short
A nitrogen-rich, certified organic plant food supplying 13% nitrogen, made from fermented plant sugars. It greens up leafy vegetables, brassicas and lawns quickly, then keeps feeding for around six weeks. High in sulphur, low in salt, and entirely plant-based.
Certified Organic 13% Nitrogen Plant-Based High in Sulphur Low Chloride & Salt Fast + Slow Release
Nitrogen Extract is a certified organic, high-nitrogen fertiliser supplying 13% nitrogen as amino acids and proteins — the form plants and soil microbes use to build leaves, stems and chlorophyll. It is made from fermented plant sugars (molasses), with the nitrogen-rich proteins drawn off and dried into a clean 3 mm granule (sometimes sold as nitrogen pellets). A natural, plant-based source of nitrogen, certified organic and made in the UK.
Unlike fast synthetic salts such as ammonium nitrate, the nitrogen here is held in plant proteins. Roughly half is available within the first couple of weeks for a quick green-up, and the rest releases steadily over the following weeks as soil biology breaks the granule down. You get the speed of a feed and the staying power of an amendment, in one plant-based granule that is also high in sulphur and very low in chloride and salt.
13%Nitrogen (N)
~50%Released in 14 days
6+ weeksSustained feed
100%Plant-based
What a high-nitrogen plant food is used for in the garden
- Leafy vegetables and brassicas — lettuce, spinach, chard, cabbage, kale, sprouts and other crops grown for their foliage respond fast to available nitrogen, putting on bigger, deeper-green leaves
- Spring green-up and growth spurts — a targeted nitrogen boost for plants that have stalled, paled, or need to bulk up early in the season before they flower or fruit
- Lawns — a high-nitrogen lawn feed that drives strong green colour and dense growth; the slow-release tail keeps the lawn fed for weeks rather than a single flush and crash
- Hungry feeders mid-season — sweetcorn, courgettes, squash and similar crops that draw heavily on nitrogen during their main growth phase
- Correcting nitrogen deficiency — pale or yellowing lower leaves, slow growth and weak stems are classic nitrogen-hunger signs that this addresses directly
- Topping up the green stage of a feeding plan — use it for early leaf and stem building, then switch to a balanced or high-potash feed as plants move into flower and fruit
A plant-based nitrogen with the kick of a feed and the patience of an amendment.
How it compares
Nitrogen Extract (this product)
- 13% nitrogen, certified organic and plant-based — from fermented plant sugars
- Amino-acid and protein nitrogen plus organic carbon and humic substances that feed soil life
- Fast start then a slow-release tail over several weeks
- High in sulphur, very low in chloride and salt — a low risk of salt build-up
- No strong smell, clean to handle and store
Synthetic nitrogen (ammonium nitrate, urea)
- A salt feed — fast, but prone to leaching and, with urea, loss to the air as ammonia
- Feeds the plant but not the soil; adds no carbon and no biology
- Higher salt index, so more risk of scorch and salt build-up if overdone
- Not permitted in organic growing
Dr Forest — made by growers, backed by science. Certified organic, plant-based, and packed in recyclable, home-compostable paper.
The science of amino-acid nitrogen: why the form of nitrogen matters as much as the amount
Plants don't only eat nitrate
For most of the last century the textbook view was that plants take up nitrogen only as nitrate or ammonium — mineral forms — and that organic nitrogen has to be broken down by microbes into those minerals first. That view is now out of date. Plants take up intact amino acids and small peptides directly through their roots, and in many soils organic nitrogen is a significant part of what they actually use (Näsholm et al., 1998; Näsholm, Kielland & Ganeteg, 2009).
That is what this product supplies. The nitrogen here is held in amino acids and proteins, drawn from fermented plant material and concentrated into a granule. Some is taken up directly; the rest is mineralised by soil biology at a measured pace. The result is a feed that works with the soil rather than flooding it.
Why plant-based amino-acid nitrogen behaves differently
What's in the granule
- Nitrogen (13%) as amino acids and proteins — both directly available and microbially released
- Sulphur (as SO₃) — needed to build proteins and chlorophyll; nitrogen and sulphur work together, and a sulphur shortfall limits how well plants use nitrogen
- Organic carbon and humic substances — food and habitat for the soil microbes that cycle nutrients
- Trace elements and micronutrients carried through from the plant source material
- Very low chloride and salt — a low salt index, so little risk of osmotic stress or salt build-up
Why that matters in the soil
- Less waste: nitrate leaches readily and urea can gas off as ammonia; protein-bound nitrogen is held until biology releases it (Cameron, Di & Moir, 2013)
- Feeds biology, not just the plant: the carbon and humic fraction supports the microbes that drive nutrient cycling and build soil organic matter (Nardi et al., 2009; Ferro et al., 2022)
- Lower nitrate loading than synthetic nitrogen, with comparable growth when organic and mineral inputs are compared (Cardarelli et al., 2023)
- Sulphur in the same granule removes a common hidden limit on nitrogen use efficiency (Marschner, 2012)
Four mechanisms of action
01
Direct amino-acid uptake
Roots carry transporters for amino acids and short peptides and absorb them intact, short-cutting part of the soil nitrogen cycle. This is most useful in cooler soils and early in the season, when microbial mineralisation of nitrogen is slow and mineral nitrogen is scarce (Näsholm et al., 1998; 2009).
02
Dual-speed release
Around half of the nitrogen becomes available within roughly the first fortnight for a visible green-up, and the remainder releases gradually over several weeks as soil organisms digest the protein. One application feeds across a growth phase rather than spiking and crashing — and there is far less to leach away between feeds.
03
Nitrogen and sulphur together
Proteins and chlorophyll are built from both nitrogen and sulphur. When sulphur is short, plants cannot fully use the nitrogen they take up, and growth and leaf colour suffer. Supplying sulphur in the same feed keeps the two in step and improves how efficiently the nitrogen is used (Marschner, 2012).
04
Carbon for the soil, not just nitrogen for the plant
The organic carbon and humic substances in the granule feed the microbial community that releases nutrients, holds them against leaching, and builds stable organic matter. Studies that pair organic inputs with growing crops consistently show higher soil organic carbon and microbial activity than mineral-only feeding (Ferro et al., 2022; Liu et al., 2021).
Scientific references
- Näsholm, T. et al. (1998). Boreal forest plants take up organic nitrogen. Nature, 392, 914–916.
- Näsholm, T., Kielland, K. & Ganeteg, U. (2009). Uptake of organic nitrogen by plants. New Phytologist, 182, 31–48.
- Cameron, K.C., Di, H.J. & Moir, J.L. (2013). Nitrogen losses from the soil/plant system: a review. Annals of Applied Biology, 162, 145–173.
- Cardarelli, M. et al. (2023). Organic vs synthetic nitrogen and nitrate accumulation. Agronomy / Frontiers in Plant Science. [nitrate reduction with organic sources]
- Nardi, S. et al. (2009). Physiological effects of humic substances on higher plants. Soil Biology & Biochemistry, 41, 1296–1307.
- Ferro, N.D. et al. (2022). Organic and mineral fertilisation and soil organic carbon. Geoderma / Soil & Tillage Research.
- Liu, J. et al. (2021). Organic amendment effects on soil enzyme activity and yield. Applied Soil Ecology.
- Marschner, H. (2012). Mineral Nutrition of Higher Plants (3rd ed.). Academic Press. [nitrogen and sulphur nutrition]
How to use Nitrogen Extract: rates for beds, lawns, containers and leafy crops
A little goes a long way
This is a concentrated 13% nitrogen feed, so it is used at much lower rates than a balanced blend or a soil conditioner. Scatter the granules evenly, keep them off leaves and stems, and water in well. Apply to moist soil during active growth. Less, more often, beats one heavy dose.
How much, and how often
One application feeds for around six weeks: roughly half the nitrogen releases in the first fortnight, the rest over the following weeks. Because of that, do not reapply more often than every five to six weeks. Across all uses, a single dressing sits between 20 and 55 g per m² (a rounded handful is roughly 30–40 g). Match the rate to how hungry the crop is, using the guide below.
Base dressing — before sowing or planting
Scatter over the bed and rake or fork lightly into the top 5–10 cm a few days before sowing or planting leafy and hungry crops. Use the lower rate on already-fertile soil, the higher rate where growth has been weak or the bed is freshly dug.
Heavy nitrogen feeders — top dressing
The hungriest leafy crops: brassicas (cabbage, cauliflower, calabrese and broccoli, Brussels sprouts, kale), leeks, sweetcorn, courgettes, squash and pumpkins, rhubarb, and spinach and chard. Scatter around the plants, keep granules off the foliage, work in lightly and water in. Two to three feeds across the season is usually plenty; stop once growth is strong and well coloured.
Salad and moderate leafy crops — top dressing
Lettuce and salad leaves, beetroot and chard tops, leafy herbs, and any plant showing pale lower leaves or slow, stalled growth. Lighter, more frequent feeding suits fast salad crops better than one heavy dose.
Established lawns
Spread as evenly as you can on a still day and water in well. The fast fraction greens the lawn up, the slow tail keeps it fed for weeks. Avoid applying in drought or to dry turf, and stop feeding nitrogen by late summer so you are not pushing soft growth into autumn.
New lawns and overseeding
For a new lawn, work into the top 5 cm of the prepared seedbed before sowing or laying turf. For overseeding, scatter over the area after seeding and water in thoroughly. The slow release feeds through establishment without scorching young roots.
Fruiting crops — early stage only
Tomatoes, peppers, chillies, aubergines, beans and peas need nitrogen only to build their early leaf framework. Feed during vegetative growth, then stop at first flower and switch to a high-potash feed such as Bloom 2-8-10 or Late Bloom 0-5-10, or too much nitrogen pushes leaf at the expense of fruit.
Roses and flowering shrubs — spring nudge
A single spring application drives strong early foliage. Follow with a balanced or high-potash rose feed for the flowering flush, and avoid further nitrogen later in the season.
Pots and containers
Mix into the compost when potting up leafy plants, or lightly top-dress established pots and water in. Containers hold a small soil volume, so keep to the lower rate and do not over-feed.
Easy to overdo — don't
Even with a low salt index, too much nitrogen drives soft, sappy growth that flops, attracts aphids and resists flowering and fruiting; very heavy doses on dry soil can scorch. Stick to the rates above, water in, and reach for a balanced feed once leafy growth is established.
Step by step
- Measure. A level tablespoon is roughly 15–20 g. Weigh the first few applications until you have your eye in.
- Scatter evenly. Spread thinly across the area or around the base of plants. Keep granules off leaves, stems and crowns.
- Work in lightly where you can — a shallow rake or hoe on beds; for established plants and lawns, leave on the surface.
- Water in well. Moisture starts the release and moves the first nitrogen down to the roots. If no rain is forecast within 48 hours, water the area to help the granules break down and prevent scorch.
- Repeat on schedule — no more often than every five to six weeks — through the growing season, then taper off as plants move into flower and fruit. On light, sandy soils, split feeds and keep to the lower rates. Store sealed, cool and dry.
Works well combined with…
Pair with Seaweed Meal for the trace elements and biostimulant compounds a straight nitrogen feed doesn't carry. Move to Bloom 2-8-10 or Late Bloom 0-5-10 once crops set flower and fruit. For an all-round leafy-stage feed, use alongside Veg 4-4-4. On lawns, follow with Volcanic Rock Dust to remineralise the soil beneath the turf.
In the Dr Forest living-soil programme
Within the Dr Forest living-soil programme, this is the mid-flower nitrogen booster for the Max yield build — about 0.6 g per litre of soil in total, split across two mid-flower doses. It is the lever that adds weight while potash and magnesium stay below their ceilings. See the Living Soil Kit and Refills.
Frequently asked questions about Nitrogen Extract
It is nitrogen held in the form of amino acids and proteins rather than as a mineral salt. Plants can absorb some of it directly, while soil microbes release the rest steadily. In the garden it acts as a high-nitrogen feed for leafy growth, green-up, and correcting nitrogen deficiency, with a slow-release tail that keeps feeding for several weeks.
Yes. It is certified organic and suitable for organic growing — plant-based amino-acid nitrogen derived from fermented plant sugars. It contains no synthetic nitrogen salts, and the organic carbon and humic substances in the granule feed the soil life that releases the nitrogen.
Yes — at 13% nitrogen it is one of the higher-nitrogen organic feeds available, and the plant-based amino-acid form means it greens plants up quickly without the leaching and salt build-up of synthetic nitrogen. It is best for the leaf-and-stem stage of growth: leafy greens, brassicas, sweetcorn, lawns, and any plant showing nitrogen hunger.
Yes. The nitrogen is plant-based, extracted from fermented plant sugars, so it suits growers who prefer not to use animal inputs. It also gives both a fast and a slow release in one material, and has no strong odour to attract animals to your beds and pots.
Synthetic nitrogen is a fast salt feed that leaches easily, can gas off as ammonia, and adds nothing to the soil itself. This delivers comparable green-up but holds the nitrogen in protein form until biology releases it, adds carbon and humic substances that feed soil life, and carries a much lower salt index. It is also certified for organic growing, which synthetic nitrogen is not.
Roughly half the nitrogen is available within about a fortnight, so a green-up on leafy plants is usually visible within one to two weeks in active growing conditions. The remaining nitrogen releases over the following weeks, so a single application keeps feeding rather than spiking and fading. Speed depends on soil temperature and moisture — it is faster in warm, moist soil.
It has a low salt index, so it is far gentler than synthetic nitrogen, but it is still a concentrated 13% feed. Keep the granules off foliage, stems and crowns, stick to the stated rates, and water in well. The main risk is over-application: too much nitrogen drives soft growth that flops and attracts aphids, and heavy doses on dry soil can scorch.
Yes, on edibles, ornamentals and lawns. It shines on leafy and hungry crops and during early, leafy growth. Go easy on flowering and fruiting plants once they have set buds — too much nitrogen then pushes leaves at the expense of flowers and fruit, so switch to a balanced or high-potash feed at that stage.
It is a plant-based feed with a low salt content, and it has no strong smell to attract animals. As with any fertiliser, store it out of reach of children and pets, keep them off treated areas until it has been watered in, and wash your hands after handling.
The nitrogen is plant-based, extracted from fermented plant sugars (molasses) and dried into a clean granule. Keep it sealed in a cool, dry place; the granule is low in salt and stores well. Packed in recyclable, home-compostable paper.
The classic signs are pale or yellowing lower (older) leaves, slow or stunted growth, and thin, weak stems — nitrogen is mobile in the plant, so hunger shows in the oldest leaves first. A high-nitrogen feed like this corrects it: roughly half the nitrogen is available within a fortnight for a quick green-up, with the rest released over the following weeks. Apply at the stated rate, water in, and avoid over-applying, as too much nitrogen brings its own problems.
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