Trench Composting

Trench composting is an underused way to improve your soil texture and add fertility to your soil. And it has the added bonus of getting rid of those tough old stems of spent sunflowers, sweetcorn and brassicas. We spent a day trench composting the quarter of our allotment in which we shall be growing our roots next year. Many books tell us not to add manure or humus to the patch where you are planning to grow your root crops but we have found by experience that if the trenching is carried out in early autumn it works just fine. As the depth of soil on our plot is less than a border fork deep we need to keep adding to it in an attempt to build up some depth.

The job gets started as Jude, aka Mrs Greenbench or The Undergardener, takes out a 2 foot wide trench down to the hard layer of boulder clay. I then follow on with the rotovator breaking up this hard packed layer of clay and large pebbles. It makes the rotovator work hard and it jumps and lurches around at the bottom of the trench. By doing this we hope to gain depth and let worms and other creatures of the soil work in the humus we will be adding. While the rotovator turns up the stones and pebbles we collect them up to use as a stonepile, a beetle shelter. The beetles are useful predators who will help in our pest control.

Green waste from the spent crops on the plot are then placed all along the bottom of the trench, with the tougher material needing chopping with a sharp stainless steel spade. Even the toughest of green waste such as brassica stalks, sunflower stems and sweetcorn stalks will break down in the depths of the trench. We also add shredded paper (only non-glossy), torn card board and lawn mowings.

To further improve soil texture and add more nutrient value we  mix in a barrow load of quality farmyard manure.We find this encourages the soil critters to get going.

To finish Jude replaces the soil over the top of the material in the trench and as a final touch we add a thick mulch of farmyard manure.

We then hand the trench with its added ingredients over to the creatures of the soil. When we trench again in a few years time all that material will have totally broken down.

We carry on by digging out another trench alongside the first and keep moving over the area until it has all been trenched. We have our plot divided into four sections to allow for crop rotation so we trench one or two sections each year. This method of composting is a very efficient way of recycling green waste including the tough materials often thrown in refuse bins. Plants grown in the richly textured and nutrient rich soil will grow strongly and therefore be healthier so will be better able to cope with attacks from pests and diseases.