Allotment Tasks – Warming the Soil

Of the not-very-many things to be done on an allotment in January, warming the soil is perhaps one of the most important and most neglected. And we’re just starting to think about warming ours, having finally dug enough of it to actually think we might get some crops in!

The point about warming the soil is that it helps germination by two means: it absorbs the warmth of the sun in the day, and slows down the loss of that heat at night, which can protect from frosts. If you have hardy crops like carrot, they will germinate in the soil at around 8 degrees Celsius but tender crops like French beans won’t germinate until soil temperature is 12 degrees Celsius – and remember that air temperature tends to be at least a degree above soil temperature and may be as much as three degrees higher than clay soils. Dry soils warm faster because water holds the cold, so having raised beds with good drainage can improve germination if you have a heavy soil

There are two ways to really warm your soil: the first is adding compost or manure which both breaks up heavy soils, giving them less water trapping, and tends to change the albedo (surface colour to us simple folk) making it darker and therefore more inclined to take in, rather than reflect back, the sun’s rays.

The second thing, of course, is to cover the soil with glass, plastic or cloches. Clear plastic is reckoned to be the best option, and this kind of cloche can be lifted easily to hoe out the weed seedlings, which will germinate very fast, and that’s always great news because once those seeds have germinated and you’ve chopped the seedlings in two, they can’t come back to strangle your plant seeds when you do put them in the ground. So quite obviously, the ideal situation is to put down your cloches a couple of weeks before you plan to sow seed, and get ruthless with the weedlings when they appear.

So why, I wonder, don’t we have any cloches … possibly because we are ill-organised and spend too much time chatting. Oh dear, oh dear, I can see allotment-holder-failure on the horizon!

Labels: allotment-cloches, allotment-seedlings, allotment-soil