|
|
The cultivated vegetable crops that we grow generally demand very high levels of soil fertility as compared to wild plants, and so we need to replenish the soil nutrients regularly in our vegetable beds. There are basically four ways to do this:
- applying synthetic chemical fertiliser
- applying animal manures
- applying compost
- growing & tilling in ‘green manures’
We don’t use synthetic fertiliser. We think it’s unsustainable and environmentally damaging because it uses large amounts of fossil fuel in its manufacture, as well as causing environmental damage through nitrate runoff. It’s also a kind of plant ‘junk food’ that gives the plants the specific chemical nutrients they need without enhancing (in fact, probably degrading) the broader biological life of the soil upon which the plants (and ourselves) ultimately depend.
We’ve used all of the other three methods to establish our site – we’ve added chicken and pig manure from our own animals, and brought in horse and cow manure from other farms. And we’ve used various composts – spent mushroom compost and municipal compost that we’ve bought in, as well as our own compost from grass, plant residues and the comfrey that we grow. In the long term, though, we’re trying to move as much as possible to using fertility-building crops grown onsite because, quite apart from the expense, there are various drawbacks to the bought-in composts. Bought-in composts are bulky and therefore have a high fossil fuel cost in transport, and we’ve found that bought-in manures in particular add significantly to the weed burden, as well as causing runoff problems if not carefully handled. Also, even though these manures and composts are widely available at the moment, they are to a large extent ultimately the products of unsustainable practices on other farms which buy in fertility in the form of chemical fertiliser and then sell it on as manure or compost, only to square the circle by buying in more fertiliser.
Our long-term aim is to make our vegetable cultivation as self-sustaining as possible, which means building fertility onsite. We therefore sow a variety of fertility-building crops – clovers, mustard, rye, buckwheat, ryegrass and so on – in between or underneath our food crops, and then either compost these ‘green manures’ and add them to our vegetable beds or till in the residues to build up the organic matter in the soil where we grow the vegetables (see the Tillage page for more discussion on the issues involved here). Growing green manures also helps to protect the soil during the winter, when a lot of soil fertility can otherwise be lost by leaching. There’s quite an art to green manuring, and we feel as though we still have a lot to learn. We’ll probably continue to buy in some composts, but we hope to minimise this over the coming years. |
