Seaweed Extract Dose & Kelp Biostimulant per Tank
Boosts rooting
Seaweed (kelp) extract is a biostimulant sprayed at a few mL per litre to boost rooting, flowering and stress tolerance — enter your spray to get the extract overall and per tank.
Mix your seaweed spray
Next: measure 45 mL of extract into each of your 14 tank loads, agitate well, and spray in the cool early morning or evening for best uptake.
Always follow the product label — recommended rates vary by formulation (liquid vs soluble flake) and crop stage. Do a small jar-test first if tank-mixing with other inputs.
Seaweed extract dose — key facts
- Extract
- spray volume × dose rate
- Per tank
- extract ÷ number of tanks
- Typical rate
- ≈ 2–5 mL/L (check label)
- What it is
- biostimulant, not a fertilizer
- Boosts
- rooting, flowering, stress tolerance
- Spray timing
- cool morning or evening
- Frequency
- every 1–3 weeks at key stages
- Privacy
- Runs in your browser; nothing uploaded
A little kelp goes a long way
Seaweed extract isn't a fertilizer — it's a tonic. The natural growth hormones, polysaccharides and trace elements in kelp stimulate roots and shoots, improve flowering and fruit set, and help plants shrug off heat, drought and transplant stress. Because it's so concentrated, you only spray a few millilitres per litre, which makes measuring the right dose — and dividing it across tank-loads — easy to get wrong by eye.
This tool gives the extract in mL and litres, the number of tanks and the dose per tank from your spray volume, rate and tank size, so you can mix consistently and never over-apply. Pair it with the Micronutrient Spray, Foliar Urea Spray and Compost Tea tools for a complete foliar program.
Mix the right dose
A few mL per litre, measured not guessed.
Fill tank by tank
Know the extract to add each fill.
Avoid over-applying
More isn't better with biostimulants.
Time the boost
Spray at rooting, flowering and stress.
Frequently Asked Questions
What is seaweed extract used for?+
Seaweed (kelp) extract is a biostimulant rich in natural growth hormones, polysaccharides and trace elements, sprayed at a few millilitres per litre to boost rooting, flowering, fruit set and tolerance to drought, heat and transplant stress. It is not a fertilizer — it is a tonic that helps the plant use nutrients and cope with stress more effectively.
How is the dose calculated?+
From your spray volume and the dose rate in mL per litre, the tool gives the total extract to add and the volume in litres, plus how many tank-loads that makes and the extract to add to each tank. For example 3 mL/L over 200 litres of spray needs 600 mL of extract, split across however many tanks your sprayer holds.
How many mL per litre should I use?+
Typical foliar rates are a few mL per litre — often 2–5 mL/L, but always follow the product label, because concentrates vary widely. Start at the lower end for tender crops and seedlings, and never exceed the recommended rate: more is not better with biostimulants and can scorch foliage.
When should I spray seaweed extract?+
Spray at key growth stages — after transplanting, before and during flowering and fruit set, and ahead of stress like heat or drought — usually every 1–3 weeks. Apply in the cool of early morning or evening so the spray stays on the leaf longer and avoids midday scorch, ensuring good coverage on both leaf surfaces.
Why work the dose out per tank?+
Most sprays are mixed one tank at a time, so knowing the extract per tank lets you measure accurately without recalculating each fill — especially when the total dose doesn't divide evenly into your tank size. The tool gives both the overall amount and the per-tank dose so you can mix consistently.
Can I mix seaweed extract with other inputs?+
Often yes — seaweed extract is frequently tank-mixed with micronutrients or foliar feeds and can improve their uptake. But compatibility varies, so do a small jar test first, add products in the right order, and follow labels. Avoid mixing with strongly alkaline products that can break down the extract's active compounds.
Is seaweed extract a fertilizer?+
No — its nutrient content is low, so it won't replace your N, P and K. It works as a biostimulant: the hormones (auxins, cytokinins) and trace elements stimulate root and shoot growth, improve stress tolerance and help the plant make better use of the nutrients you do supply. Use it alongside, not instead of, fertilizer.
Does foliar or soil application matter?+
Both work. Foliar sprays act fast on the canopy and are ideal for stress and flowering boosts; soil or fertigation drenches feed the root zone and soil biology over a longer period. This tool sizes a foliar spray, but the same dose-rate logic applies if you're drenching — just match the rate to the product label.
Are the figures precise?+
They're solid mixing quantities from your volume, rate and tank size. Always defer to the product label, since concentrates differ greatly in strength. Measure carefully, test on a few plants first, and adjust the rate to your crop and conditions rather than treating any single figure as fixed.