Once upon a time, fertilizing your veg patch would have been a simple business. Farm animals and draft horses were common, and the Victorian kitchen gardens from which most gardening advice seems to stem were part of estates with great piles of manure. Elsewhere in the world, farmers had to be more enterprising; in China it was common to collect ‘night soil’ to spread on fields. It happens here today, but we prefer our sewage to be safely treated before it becomes an agricultural additive.
For most home gardeners, though, fertility tends to come out of a bag or a packet. Unless you have a riding stables nearby, you’re unlikely to get your hands on ‘well-rotted manure’ in large quantities, and increasingly there are worries about it being contaminated with chemicals and pesticides that harm your veggies.
If you do get your hands on manure then it’s important to compost it yourself unless it has been stored long enough to rot down. Composting stabilizes the nutrients so that they are not washed away by rain, and also ensures that the composting process doesn’t lock up nutrients in the soil – exactly the opposite of what you’re trying to achieve by adding a fertilizer! Three to six months on the compost heap also minimizes any problems with contamination.
Well-rotted manure is a high fertility soil improver, meaning that it feeds your plants, but also contains enough organic matter to improve the soil. You can usually buy manure in bags from the garden centre, but a homemade alternative is to make as much compost in your garden as possible. Compost isn’t such a highly concentrated fertilizer (unless it’s worm compost, made from kitchen waste), but it’s a brilliant soil improver and contains a wide range of nutrients for your plants.
Plants need a balanced diet. Commercial fertilizers display their NPK ratio on the packet. Nitrogen (N) encourages strong leaf growth. High levels of nitrogen are good for leafy vegetables and for other plants in the spring. Phosphate (P) encourages strong root growth and Potassium (Potash, K) promotes fruiting and flowering. These are the three macronutrients; plants also need smaller amounts of a range of micronutrients – a bit like the way we need vitamins and minerals in addition to fats, proteins and sugars.
But rather than reaching for commercial products when it’s time for supplementary feeding (for hungry crops, or plants in containers), it’s possible to make your own homegrown versions. The best news is that it can also help with your weed problems!
The usual choice for a high nitrogen liquid feed is nettles. When the nettles are growing rapidly in spring, just chop them down and rot them down in a bucket of water. Once it’s brown and smelly you can water it down as a liquid feed for anything that needs it.
An alternative source of nitrogen for gardeners is pelleted chicken manure, which is a safe and storable fertilizer. It does pong, but there’s an advantage to that. You can use it to cover up the smell of anywhere cats have ‘done their business’, and discourage them from using your garden as a toilet again! It’s potent stuff, best used sparingly, but adding a handful to containers, or planting holes, can give plants a good boost.
For a high potassium feed – good for fruiting vegetables such as tomatoes and peppers – you can do the same thing with comfrey. But be warned! It stinks to high heaven. Your neighbours will think you’ve opened a sewage works at the bottom of the garden. A better way to deal with comfrey leaves (and it only works for comfrey leaves) is to allow them to rot down without adding water, in a lidded container. It takes a few weeks, but gives you a concentrated brown liquid that doesn’t smell much and is easy to store. Dilute it when you feed your plants – you’re aiming for something the colour of weak tea. You may find comfrey growing wild in your local area, but you can also plant it. The sterile cultivar Bocking 14 is recommended for gardens, because it doesn’t set seed.
Organic sources of phosphate (P) include bonemeal and rock phosphate, but you’re unlikely to need too much in the veg patch, especially if you make your own compost. And if you encourage wild birds into the garden – one of the best sources of phosphate is bird poop! (If you’re a meat eater then you could consider recycling animal bones into your own bonemeal; human urine is also a good source of phosphate….)
To add trace nutrients, use seaweed. If you’re lucky enough to live near the coast then you can collect your own (but check the local by-laws, don’t harvest more than you need, and check the tide timetable!), which can be applied directly to the soil. For the rest of us it’s possible to buy seaweed-based liquid feeds. Think of them as vitamin pills for plants. You can water them down or apply them (highly diluted) directly to the leaves as a spray.
Emma Cooper has been gardening, and blogging, since the dawn of the new millennium. She’s utterly smitten with edible and useful plants, and is never happier than when she’s in the garden, up to her elbows in compost. She’s in the process of building a new garden, and you can follow her progress on her gardening blog, The Unconventional Gardener.