On a visit to our friends’ house recently, the subject of food waste came up. They haven’t got a tucked-away spot to set up a compost bin or heap in their garden, and their local council doesn’t collect. They had put their effort into bokashi composting in the past, but with a baby on the way I suspect they’ll have more than enough to do without taking on the added responsibility of caring for a bucket of fermenting kitchen scraps.
But as they’re already accustomed to burying their bokashi-ed vegetable peelings, it got me thinking about how low effort and high impact trench composting can be for those without room for a larger system. Trench composting is the simple process of putting your compostable matter – fruit and vegetable waste, plant material from the garden, grass clippings, leaves, etc – into a trench near where you’re planning to grow your crops next year. Over the coming months, this organic matter will slowly decompose, enriching the soil and improving its structure, making it ready to welcome the following season’s plants. No further effort is required from you to engage in this ancient approach.
It’s possible to compost this way in a relatively shallow trench, although some advice suggests digging down to 60cm (2ft) before adding the organic matter and covering the trough. If you take a shallower approach, consider covering your trench in a tarpaulin and pinning it down firmly to prevent your beds from being dug up by the hungry creatures that visit your garden.
Another benefit of trench composting is that you won’t be worrying whether you’ve achieved the right proportion of greens and browns. As anyone who has tended to a stagnant or dormant compost heap knows, it can be tricky to get that balance right, but trench composting is more forgiving. It is best to incorporate a mixture of green (nitrogen-rich) material and brown (carbon-rich) material as you would in a traditional composting setup, but you can be looser with the ratios.
As a fairly devoted practitioner of no-dig growing, I wince at the prospect of digging a trench alongside or into my veg beds, but I think it’s possible to excavate a decent amount of earth without entirely disrupting the soil horizons. I would consider trench composting when redoing a perennial bed or doing extensive removal of perennial weeds, as both require me to disrupt the soil anyway. Whenever I am called upon to dig, I’m careful to replace the soil from where it was unearthed as best I can and avoid moving soil when it is saturated.
Trench composting is really worth considering if you’re building raised beds in your veg patch as you can add a layer of compostable material before filling your beds – no digging required.
