How to Make and Use Home-grown Fertiliser

, written by gb flag

Comfrey is a great home grown fertiliser

Is it necessary to use fertiliser to grow vegetables? Well, we all dream of perfect soil, bursting with life and humus, supplying all the nutrients the plants need. Our article Feeding, Fertilisers and Fertility last year made the point that if the soil is looked after, then crops grown in the open (as opposed to in containers) need little fertiliser. In fact, fascinatingly, recent research found, not only that the flavanoid level in organic tomatoes increased with an increased level of organic matter in the soil, but, once soil reached its ideal condition, required reduced applications of manure in order to maintain that increase.

However, not many of us can claim to have perfect soil and if it’s a difficult year weather-wise (any nitrogen available to plants in the soil is easily washed away in heavy rain), you have difficulty generating enough organic matter to spread on your beds, or you grow mostly heavy-feeding vegetables like brassicas, giving them extra nutrients along the way will keep them growing steadily through the season, give them strength against pests, and produce a better harvest. You just don’t want to overdo it.

The good thing is that fertiliser doesn’t have to come in expensive packets from the local garden centre, as we can grow our own. Comfrey and nettles are the most obvious home-grown fertilisers, but all organic matter feeds the soil. A mulch of grass clippings makes a supplemental fertiliser and weeds soaked in water will produce a liquid feed of some value, which is one way of getting your own back on them.

In fact, it’s recently dawned on me why straw is a traditional mulch for strawberries and potatoes. Straw, whether of wheat, oat, oilseed rape, rye etc., is high in potash which will be released as the straw rots down, and both these crops love their potash.

Watering on a homegrown liquid fertiliser

Fast and slow fertilisers

If you do decide to grow your own fertiliser, how is it best to use it? Well, fertilisers are generally described as fast- or slow-acting and those used by organic gardeners are generally slow-acting—broken down gradually by soil micro-organisms, providing food over a much longer period, often beyond the current growing season.

Liquid fertiliser is different. The nutrients have already been released into the water and are therefore readily available to plants. What liquid fertiliser shouldn’t be is a substitute for good soil. It is useful, though, while you build up the quality of your soil with organic matter.

How to use your home-grown fertiliser

The great thing about growing your own fertiliser is that you have a choice—you have a fertiliser that you can apply in different ways, depending on the need at the time.

Adding compost to the soil around, for example, your brassicas can’t be expected to deliver nutrients quickly to the hungry crop. In fact, it’s worth noting that composted manure gives more nitrogen to plants in the second and third year after application, because the micro-organisms take time to release it.

Nitrogen-rich plants such as nettles and comfrey will provide nutrients faster, over weeks, as they decompose quickly (which is why they are often used to fire up compost heaps), so add these to your beds from the start of the season, and as and when they need a top up. Just chop up the leaves and mulch around your plants (or lay whole leaves on the soil for slightly slower decomposition).

A liquid feed is the instant tonic of the plant world. Make compost tea by soaking a bag of well-rotted compost in a large bucket of water for about ten days, or nettle or comfrey tea by soaking leaves in a bucket for three weeks or so, and you’ll have a solution that, diluted with water to the colour of weak tea, will deliver a nutrient-rich tonic quickly to the vegetable roots.

Liquid fertiliser

Be careful with liquid fertiliser

One thing you don’t want to do is overfeed your plants. This is most likely to happen with too much liquid fertiliser. When I’ve just made a huge bucketful, I find it awfully tempting to keeping sprinkling it around.

Keep an eye on your vegetables and if something looks to be flagging, and doesn’t respond to a good water, then try a liquid feed. Vegetables need more nutrients when they’re using the most energy, so broccoli and cauliflowers, for example, will appreciate a bit extra as they begin to head up. Tomatoes, capsicum, aubergines, cucumbers—all these heavy bearers appreciate extra nutrients. Overwintered crops will benefit from a boost in early spring when they start to get going.

Root vegetables generally manage well on what’s in the soil and don’t waste the precious liquid on seedlings. They shouldn’t be encouraged to grow too fast, and might be affected by a fungal infection in the water.

Salads always look as if they’ll appreciated a lot of nitrogen (it’s all those green leaves), but they aren’t particularly greedy, so on the whole I don’t give them any tea. Cut-and-come-again crops do expend extra energy, though, and if they’re looking tired I feed them once a week with nettle or compost tea until they’re looking perkier. On the whole, I prefer to mulch salads with nettles or grass clippings, and build up the soil for the following years with compost, to give a more measured approach, as too much nitrogen given to leafy crops will make them grow soft and sappy and more vulnerable to pests.

It’s also worth remembering that comfrey tea majors on potash, which encourages fruiting and seeding, so if you apply it to saladings you might find them running to seed more quickly.

By Helen Gazeley

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Show Comments


"I'm currently reading the Smiling Gardener's new book on Building Soils Naturally and a point that he makes is that being successful at making compost tea is a rather complex project. There are many things that can go wrong with it. There may be some benefit to compost soaked in water, but more often than not, you are wasting your time. My own experience has show that I haven't been very successful at making helpful compost tea, even though I've tried to do everything right."
Bill Brikiatis on Friday 3 August 2012
"Hi, Bill. Compost tea is a term that applies to two different types. One is the simple, soak-in-a-bucket extraction of the goodness of a plant; the other is a fermented brew with oxygen bubbled through it, which aims to increase the numbers of micro-organisms in the solution before adding it to the soil. Quite a bit of argument exists as to whether it's worth brewing compost tea, especially in the domestic setting. "
Helen Gazeley on Friday 3 August 2012
"I am trying to grow vegetables /fruit bushes in raised beds which are situated right at the edge of my woodland area. I have had very little success despite using fertiliser from wormary and own home made compost. I have been advised that the trees are taking all the nutrients from the soil. Should I give up on the raised beds and use pots?"
shona Mackenzie on Friday 3 August 2012
"Shona, I suspect that your vegetables aren't getting enough light and/or water because of the overhanging trees. "
Helen Gazeley on Saturday 4 August 2012
"I've been wondering what to do with my little patch of butterfly-friendly nettles and you've just given me the perfect idea! Thanks :)"
Kimberley on Thursday 9 August 2012
"I have awful clay soil and for years have been making my own compost and adding heaps to the garden. I also use organic fertilisers and tea from my wormary. The soil has definitely improved, (I managed to grow straight carrots for the first time this summer), The problem is that my veggies don't taste great. The beets are tasteless! What can I do the rectify this?"
Debbie on Sunday 12 August 2012
"Debbie, different varieties of vegetables do perform differently, taste-wise. You may be growing varieties, for example, that tend to grow particularly large or are fast maturing where taste has been sacrificed. Have a go with other varieties (heritage varieties often yield less but have more taste), and ask around to see what your neighbours grow successfully, as what grow tastily in one type of soil may not taste so good from another type. "
Helen Gazeley on Monday 13 August 2012
"I love that Flowers has integrated our natural world into our technological world. In my own opinion, it is this kind of imagination and creativity that will help create an environment that embraces both elements to build a more harmonious world."
rohit on Thursday 16 August 2012
"An excellent and detailed article on growing your own home grow fertilisers which is 100 % organic."
Satish on Saturday 18 August 2012
"@ regards to compost tea....nettles.comfrey in fact any plant including weeds will make a good "tea"..Just make sure that what you use rots down in the water before you use it..If you can use an onion bag or similar the "leftovers" can be added to the compost heap or used as a mulch.It really is worthwhile doing it but don't expect immediate results as, obviously the tea has to work its way into the soil before it can take effect.Once it does you can expect good results..My "Runners" love it !...Have fun .."
melboy24 on Friday 7 September 2012
" @ Bill again...if you use a dustbin to make your tea just remember when you take the lid off...hold your breath !!"
melboy24 on Friday 7 September 2012
"I am wondering about using my home made compost. Is it OK to apply it in the fall or will winter snows and melts just leach the nutrients out of the soil before I get to plant anything in the spring? I feel like doing it now, but wonder if I would be wasting my time and lovely compost. And to keep it over the winter, what would be the best way, so that again, it doesn't leach into the soil around it?"
Judy on Friday 5 October 2012
"Judy, it's fine to apply during the fall. On the whole, the nutrients in the compost rely on soil bacteria to release them, so they won't all get washed away during the winter. "
Helen Gazeley on Friday 5 October 2012
"Some truly wonderful posts on this internet site , thank you for contribution. "
Gravel dealers alabama on Saturday 14 September 2013
"I'm using nettle tea on onions,pots,and tomatoes is it wise.I thought I would feed once a fortnight"
merv on Tuesday 28 April 2015
"i take a pickup of horse manure, a pickup of seaweed from the coast and a pickup of leaves and some kitchen scraps. i layer it over and over. then 6 mo. later apply this beautiful dark humus to my garden rows.could you please advise what else i could be adding to make it more compplete so as not to have to use much expensive organic store bought fertilizer?"
carnen on Wednesday 30 September 2015
"Wow, that sounds like an incredible recipe for compost! The more home-made garden compost you can use, the better (cost-wise). You could also try ripping up cardboard and adding light shredded prunings."
Ben Vanheems on Friday 2 October 2015

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