I so believe in building a trench bed to improve extremely poor soil before planting seedlings.
A trench bed is like a compost bin, dug into the ground and consisting of alternate layers of fresh green ‘live’ organic material, brown ‘dead’ organic material, fresh manure and soil. NOTE that each layer of dead or live organic matter is covered with soil & watered before another layer is added.
Trench beds are also worth considering if you live in a dry climate. The result is water retention, good soil aeration and an on-going supply of nutrients for micro-organisms and plants.
Gather a spade, water (hosepipe or buckets), live organic matter in bags/piles: green garden and kitchen waste, moist seaweed, horse or cow manure or any other fresh untreated organic matter, dead organic material in bags/piles: newspaper, sticks, dead leaves & cuttings and any other dried out organic material. Compost is optional if you want to plant soon. You will also need four 1/2 metre long sticks (to be used as markers).
Measure out your trench (however long you like but no wider than a metre (for easy reach). Dig out 30cm of top soil (pile it besides the trench, remove stones).
Dig another 30cm of sub-soil (create a separate pile and remove any stones).
Loosen the base of the trench with a garden fork.
Cover the base and sides of the trench with cardboard or newspaper. Moisten with some water.
Lay sticks on the bottom (or other rough material) up to a height of 20cm.
Place 10cm of your subsoil over the sticks. Give a light shower of water.
Place 10cm of dry/dead organic material over the subsoil. Water lightly again.
Lay 10cm of green/colourful live material over the brown material (I included rinsed seaweed), cover with a layer of soil and water.
Place bits of horse or cow manure over the green layer and water, add some soil & water.
Repeat the layering process until your trench is full (leave out the stick step).
Place 1/2 metre long sticks at each corner of the trench to use as markers.
Place the topsoil you dug out earlier over the top. The bed will now stand about 20cm higher than the ground but will drop with time. Add compost (one bucket of compost per m2), level out & water well.
Place a mulch of your choice onto the ‘skin’ of the soil to protect it.
The bed is ready to be planted (wait for a month if you prefer to leave out the composting step). Just add a little patience and before long, you’ll be so glad you put in the effort (still can’t get over the spinach)!
Once your plants have taken, feed them with a liquid natural home-made fertiliser every week or so and compost every now and again. Avoid walking on the bed to keep it soft and aerated.