In an organic garden, it is crucial to think long-term. Learning how to make your own liquid fertilizer or plant food is one of the many ways to ensure your garden works not just now, but well into the future. Liquid fertilizers are one of a number of organic gardening practices that you can use to feed your plants, and the soil they depend on. Liquid fertilizers can help you make the most of whatever gardening space you have available.
What is Liquid Fertilizer and Why Use It?
Liquid fertilizer or plant food is any form of ‘drink’ that you give to your plants. Just like us, plants need food and drink in order to survive. They may not need quite the same things as we do to sustain their growth and stay alive – but the basic principles remain the same. Liquid fertilizers are formulated to give plants what they need. It will serve as a delivery system to give plants nutrients, either through their leaves, as a foliar feed, or through the soil and a plant’s root system.
In addition to being used to feed individual plants, which are growing either in the soil or in containers, liquid plant fertilizer can also be used to give a more generalised boost to a growing area. It can be a quick way to increase the nutrient content in soil or growing medium.
The Best Liquid Fertilizer
There are a wide range of different liquid fertilizer or plant food options. Below are some of the many different alternatives that you can consider using on your plants and in your garden:
Compost in a container, ready to make compost tea.
One of the most obvious ways to return nutrients to your garden is through composting. You can compost fruit and vegetable scraps from your kitchen. In addition, you can add other compostable materials from your home, and other organic matter from your garden. There are a range of different ways to make your own compost at home.
What you may not realise is that you can also use homemade compost to create a feed to return nutrients to the system more quickly. This simply involves adding compost to water, leaving it for a while for the nutrients to enter the solution, and then straining the solution and using it, diluted as required, to water your plants.
To make compost tea:
- Make a good quality compost.
- Sift the mix to remove large stones, twigs and non-composted material.
- Fill a container (such as a 5 gallon bucket) 1/3 full of this compost.
- Top up the rest of the container with water (ideally rainwater rather than water from the tap).
- Stir the mixture well.
- Leave the mix for a week or two (covered) to mature.
- Strain the fluid and use it on your plants right away (so nutrients are not lost).
Place this mix in a watering can and use the compost tea that you have created to water as you would usually do around the base of your plants. You can also consider placing the compost tea in a plant sprayer or mister and using it as a foliar feed – spraying it directly onto the leaves of your plants to give them a quick boost.
Liquid Fertilizer From a Wormery
One slight variation to this is the solution that you can create when you compost with the aid of special composting worms. One great way of composting kitchen waste is in a wormery. In a wormery, special worms help in breaking down and aerating the compost, so it is made more quickly. The compost created is enriched with ‘worm castings’ – basically, worm poo. This is a great soil amender.
Wormeries often come complete with a faucet to drain off excess fluid from the compost. Home-made wormeries can also be constructed, and it is best to include a way to drain off the excess fluid.
The fluid that you drain off can also be watered down and used to make food for your plants.
Liquid Fertilizer From Fish Waste
Interestingly, a wormery can also form part of an aquaponics system, where fish are used to fertilise water. In an aquaponics system, the water, fertilised by the fish, is used to grow plants without soil.
But if fish are kept outside of an aquaponics system, as pets for example, their waste could also be used to grow plants. The water from an aquarium can be used as another low-impact and eco-friendly fertilizer.
Plant Based Liquid Fertilizer
Comfrey is an incredibly useful plant to grow – one of its uses is to make a feed.
Plant based liquid plant feeds are another important category. By allowing plant material to decompose within water, we can create a nutrient rich ‘brew’ to return their nutrients to the natural system. Some plant based fertilizer or plant food examples include:
- General purpose weed
- Nitrogen rich nettle
- Nitrogen rich grass clippings
- Seaweed based
- Balanced ‘comfrey tea‘ – great for tomatoes and other fruiting plants.
- Miracle Gro All Purpose Plant Food – This all purpose plant food has the nutrients they need to grow
Comfrey leaves decomposed in water make a liquid feed comparable in nutrition to commercial feeds. This is one of the most efficacious plant-based liquid feeds you can make. Comfrey contains a good mixture of nitrogen, potassium and phosphorus It is quick growing, and good for your garden and its wildlife. Comfrey can generally be harvested twice over the summer months. After you cut down the plants to the base, they will regrow and provide a second yield.
To make your feed:
- Harvest the whole of the above-ground portion of the plants – the stems, leaves and flowers.
- Place your comfrey in a large container (with a lid). Chop the comfrey up into pieces to speed up the process.
- Cover the comfrey with water and put the lid on tight (as the brew really stinks!).
- Leave the comfrey to decompose for 4-6 weeks.
- Strain and dilute the mix three parts water to one part comfrey.
- Use the plant feed to water your plants, or as a foliar feed.
A similar process can be used to make a liquid feed from any other of the plant materials mentioned above.
Potash Liquid Fertilizer
Wood ash is a great source of potassium and can be great for fruiting plants. Unfortunately, if you make a feed with wood ash and water alone then the result would be strongly alkaline. This can be an option for amending soil pH in very acidic soil areas. Fortunately, for those who do not want to amend pH so extremely, there are various options for making this mix more acidic.
Fish/ Meat Based Liquid Fertilizer
Though vegetarians will be likely to want to steer clear of this one, if you eat fish you can make your own fish fertilizer using the waste by-products of the fish that you eat or whole fish if you have them available and going to waste.
If your garden is short of phosphorus then you may want to create a fertiliser that contains plenty. Meat eaters can use the bones from meat meals to make their own bone meal fertiliser. This can also be blended with water and applied to the garden in liquid form.
A bokashi bin system can also be used to ferment meat, dairy and fish along with other kitchen waste. This method can be used to create a nutrient rich tea which can be used to feed your crops, as well as a stable soil-builder that can be added to your regular compost heap or bin.
Choosing the Right Liquid Fertilizer
Whichever feeds you choose to use, it is important to choose the right option for different plants and different growing areas. A feed can give plants a boost – but choosing the wrong one can be detrimental, or even kill plants. You can also do more harm than good if you use too concentrated a solution.
When choosing feed for your plants and soil, one of the important things to consider is the balance of N (nitrogen), P (phosphorus) and K (potassium). These are the three main nutrients required in fertilizer. But plants will require different levels of these three nutrients depending on their type, characteristics and stage of growth.
Nettles are great for a nitrogen-rich liquid fertilizer
Nitrogen promotes healthy green, leafy growth and while it is important for all plants, leafy vegetables are particularly hungry for this key nutrient. A nitrogen deficiency often results in yellowing of the leaves. Sometimes leaves will also have a pinkish tint and plants can look weak and spindly. If leaves have yellowed after heavy watering, nitrogen deficiency can often be the cause, since nitrogen is very soluble and is easily washed out of the soil by over watering. Nitrogen rich feeds such as grass clippings or nettle based feeds, for example, are good to combat nitrogen deficiency. They can also give nitrogen hungry plants (leafy greens in the brassica family, for example) a boost.
Phosphorus is essential for healthy growth of shoots and roots. Phosphorus deficiencies are rare in the UK but may occur occasionally where there is heavy rain and clay soil. Symptoms include yellow, dull foliage and slow growth. Adding fish, blood or bone based feeds can help to remedy the deficiency.
Potassium is required for controlling water uptake and for photosynthesis. It promotes good flowering, fruiting and the general hardiness of your polytunnel plants. Plants suffering from potassium deficiency will tend to have yellow or purple leaf tints, browning at the leaf edges and will not flower or fruit well. Potassium shortage is more likely to occur on free-draining chalky or sandy soils, where the water soluble potassium is easily washed away, while clay soils are better at holding potassium within their structure. Potash, comfrey-based organic tomato feeds (and other organic sources of potassium such as banana skins) can be added to remedy the problem.
Watering tomatoes with a potassium rich feed.
Think about which of these three nutrients can be delivered by different feeds. Think about the balance of these nutrients required by your plants. It is important to deliver the right NPK balance, since there are a number of problems that can pop up if you get things wrong. For example, feeding a nitrogen rich feed can sometimes be counterproductive. This is because a nitrogen rich fertilizer can encourage leafy, foliar growth at the expense of flowers and fruit.
Another important thing to consider when choosing a liquid fertilizers is the pH level of the brew, and how it might affect the pH of the soil. As mentioned above, potash liquid fertilizers are one example of liquid fertilizers which can influence soil acidity. Other liquid fertilizers can also have an influence. When choosing which liquid fertilizers to use, it is important to take soil or growing medium pH into account.
Using What You Have to Hand
Making your own liquid fertilizers is a great way to live and garden more sustainably. It is a fantastic alternative to the polluting and harmful chemical fertilisers that you can buy. For anyone who cares about our planet and our future, organic gardening is a must.
But the most sustainable option is always to complete nature’s cycles in as short-circuited a way as possible. It is a good idea to use resources and materials sourced from as close to home as possible. When finding materials for liquid fertilizers, your own garden is the best place to start. Even if you do not have your own garden, you will often be able to source materials for a home-made fertilizer in your surrounding area, and use it to water your houseplants and container-grown edibles.
Make your own liquid fertilizers and watch your garden and its plants grow stronger and produce more over the coming years.
Elizabeth Waddington is a smallholder, permaculture designer and environmental consultant. When not designing food producing systems or advising growers around the world, she is to be found in her own garden. On her 1/3 of an acre patch of land she has a walled forest garden orchard (home to rescue chickens), a polyculture vegetable plot, a polytunnel, wildlife pond, wild woodland garden and more and is working every day towards greater self-sufficiency. She is passionate about sustainability and loves to inspire others about the wonderful things home gardeners can do for people and planet.