Clearing the ground
In this extract from The RHS Allotment Handbook, find out about the basic groundwork needed before you can start planting. Then roll up your sleeves and begin.
Ground clearing can look daunting, but even a full plot is only 250 sq metres (300 sq yards) and if you clear just five of those each week, the job will be done in a year.
Covering the land in need of your attention with black plastic sheeting for a growing season, or treating with glyphosate-based weedkiller will bring the ground into a more workable condition. Heavy nettle and bramble infestations can be treated with hormore weedkillers, but these remain active in the soil, so there is a delay before you can begin planting. After clearing the soil destroy all the vegetation, for example by burning ( but be sensitive to other allotment holders). Next dig over the soil to a spade's depth, getting rid of weed roots as you go.
Rotavators are an option, but beware if there are weeds present, as the blades will chop their roots into small pieces & make the problem worse.
Check the soil structure - a simple but necessary test
- Dig a pit with straight sides about 60cm (24in) deep. You should see about 25cm (10in) of dark topsoil without compressed zones.
- To check that the underlying subsoil is not rock hard and will allow water to drain, fill the pit with water, cover and leave overnight.
- If the water is gone by morning all is well; if not drainage may be a problem. This is often best addressed by raised beds.
Plants need nutrients to grow, especially nitrogen, phosphorus, potassium, and magnesium. Although generous use of organic manure evens everything out in time, a laboratory soil test is well worth investing in. It will tell you not just whether a soil is acid or alkaline, but how much phosphorus, potassium, and magnesium it contains.
This allows you to choose a fertiliser regime to meet any deficiencies. Don't bother with DIY kits for nutrients, they are often misleading.
Knowing your soil pH will allow you to choose a suitable fertiliser. If the soil is acid it will need lime to ‘sweeten’ it. Fruit likes acid soil, so aim for pH6–6.5 here, but for vegetables alkaline conditions will reduce diseases, especially club root, so aim for pH6.5–7 for these.
Use a cheap pH test kit every season and add lime to the soil if required. (See information panel, right.)
Carpet mulches and more attractive options
A mulch is any blanket of material used on soil to suppress weed growth, protect the surface from the elements, and if the mulch is of organic matter, to increase fertility and texture.
For a really attractive mulch, there’s nothing to beat a green manure or a thick layer of organic matter, but other options have other benefits.
Carpet is an old favourite for suppressing weeds. However many sites now discourage its use for fear of chemicals leaching into the soil.
Luckily there are other options. Thick cardboard is cheap, but black plastic, weed-control fabrics, and permeable mulch matting are the most common. Black mulches absorb heat and ‘cook’ weeds and seeds beneath, and the lack of light weakens anything that survives.
Perennial weeds – bindweed, couch grass, and ground elder for example – are the worst. It’s essential to eliminate these before you plant any permanent crops, such as fruit trees and asparagus.
Perennial weeds cannot stand digging. In fact, the main point of digging is to control weeds, and autumn digging can get you on top of even the worst perennial weed problem. Spot-treating with glyphosate-based weedkiller is also very effective, but no weedkiller must touch valuable plants, & crop plants are more susceptible to it than weeds.
It is very good practice to cover alleys between fruit crops with porous, opaque weedcontrol membrane. Although not cheap, it greatly reduces the weeding burden.
Although perennial weeds are most damaging to fruit and other permanent crops, it is annual weeds that trouble vegetable crops. Weed seeds remain viable for years in the soil, and many weeds can set hundreds or even thousands of seeds if allowed to mature.
You can tackle weeds by creating ‘stale seedbeds’. Break the soil down to the fine crumbly ‘tilth’ that’s needed to sow seeds at an even
shallow depth but do it a few weeks before it’s time to sow or plant. The weeds will emerge, polish them off with shallow hoeing or contact weedkiller few more will emerge that year.
You’ve been reading an extract from The RHS Allotment Handbook. Buy your copy now for just £13.99 from the RHS Shop.