Deep Mulching (aka soil lasagna)
Our community garden field was unmanaged for approximately 6 years and has a serious seed bank of weedy species seeds in the soil.
We tried tilling the first two years.
Year one we excavated the area, then tilled it. Year two we plowed the field using a tractor borrowed from a volunteer. In both years, the weeds (mostly Candaian thistle and fox-tail grass) returned in a week.
The second year after the plowing gave us little relief from the weeds, we decided to incorporate no-till methods and re-tilled the weed sprouts and started deep mulching as quickly as we could.
1 layer of cardboard
1 layer of compost or newspaper
1 layer of straw
Wet it all down and voila!
The weeds do not return nearly as quickly as with the tilling methods. Some pop up in cracks between cardboard pieces, but for the most part, what becomes impossible to keep up with turns into a manageable space.
Our community gardeners have incidentally set-up a small experiment because some chose to keep the mulching and some removed it before planting their plot. The ones who removed it had a an easily observable increase in weed invasion.
The mulching also helps us build up soil structure. This area is in a flood plain and is very nicely loamy. However it's almost too loamy. The sandy loam has very little organic matter in it and as a result:
- it does not retain water well
- it does not form peds (units or chunks of soil that plant roots can grab onto)
- it is less able to provide nutrients to plants.
Of course the weed species can overcome all of this lack of soil structure by growing large root systems adapted to drilling down deep into the soil horizon. Our garden species, not always quite so much.
This method requires one full mulching at least once a year, but ideally in spring and the autumn to prep beds and keep an advantage over the weeds.
Come help us anytime and learn more OR bring your cardboard and newspapers down to us.
We are happy to use them this way and you participate in a more meaningful way of recycling!