Making Homemade Liquid Fertilisers

In 2010 I used up my last bottle of organic liquid fertiliser concentrate, and I haven’t bought any since. Instead I have been making homemade liquid fertilisers and using them on everything – young seedlings, plants growing in containers, and sweetcorn and other veggies that benefit from a midseason booster feeding.

The material I use as a starter is locally-produced poultry manure product with a nutrient analysis of 5-4-4, which is quite similar to many of the chicken manure pellets sold in UK garden centers. I also have experimented by brewing up fertiliser solutions from several national brands of granulated organic fertiliser with excellent results.

This adventure began when I was writing an article for Mother Earth News magazine on making homemade liquid fertilisers, based on research commissioned from Woods End Laboratories. The next season I started experimenting on my own using the procedure from the Woods End study: Mix a nutritious substance with water, stir, wait two to three days, and pour off the liquid. Then you mix the fertiliser concentrate with an appropriate amount of water. This is quite similar to how many gardeners make fertiliser from comfrey, only faster. Note: It is possible that steeping comfrey for more than a week is overkill. With grass clippings and seaweed, the Woods End study showed that most nutrients had leached into the water after three days.

Making your own homemade fertiliser is straightforward enough, yet I have learned much through trial and error work with three of the materials studied in the Woods End report – processed poultry manure, grass clippings, and urine. You may wince at the latter, but except for being high in salts (which can burn plant roots), freshly collected urine mixed 1:20 with water makes an excellent high-nitrogen fertiliser of which we all have a constant supply. By the time it is properly diluted, urine fertiliser loses most of its smell.

Homemade fertilisers made with poultry manure, dry organic fertiliser or grass clippings provide a wider range of nutrients, and you can be as creative as you like in choosing materials. Grass clippings contain quite a bit of soluble nitrogen, so I often add a few handfuls when making liquid fertiliser by the bucket. Depending on how much you want to make, I have given two "recipes" below. After the liquid extract is poured off, the gunk left behind can be dumped into the compost.

One Quart Batch

For the past two springs, my seedlings have grown beautifully using this simple recipe. Place 4 tablespoons processed poultry manure or blended dry organic fertiliser into a quart jar, and fill with lukewarm water. Screw on the lid and shake vigorously, then keep at room temperature for two days. Pour off the liquid and dilute with water to the strength desired. For seedlings I use a very dilute mixture, one part extract to four parts water. With experience, you will be able to estimate the strength of the solution based on its colour.

One Gallon Batch

Once summer gets going and I have many plants in need of booster feeding, I make bucket-size batches of homemade liquid fertiliser. One batch per week meets the needs of my large veggie garden. To make it, I put one cup of processed poultry manure or blended organic fertiliser into a pail along with a few handfuls or grass clippings or chopped comfrey or stinging nettle leaves. Then I fill the pail with a gallon or so of water, stir well, and place it in the shade covered with an old towel. In two days the solution is ready to strain through a colander into another pail. I mix the concentrate with water in my watering can, diluting with about five parts water.

About the only things you can do wrong when making homemade liquid fertilisers is to use an overly strong solution, let the mixture ferment too long, or splash it on plant leaves instead of drenching roots. Always err on the side of a weak solution, because excess salts in an under-diluted extract can lead to injured roots and browned leaf edges. As for the brewing time, an unpleasant smell begins to develop after two days, and becomes downright awful after four. At this point the mixture has gone too far, and it’s time to dump it out and start over. Homemade liquid fertilisers are too biologically active to be saved or stored, so it’s best to make small batches so you always have a fresh supply. I think wild-fermented concoctions that include manure belong in the soil, not on plants, because of their heavy load of bacteria. I am careful when drenching vegetables with the stuff, and I avoid getting it on edible plant parts altogether. Going into my third season making homemade liquid fertilisers, my garden and I couldn’t be happier.

By Barbara Pleasant