At the permaculture course we attended at the Durban Botanic Gardens, we learnt about the benefits a little plant called comfrey can bring to your garden. Planted as a green manure, it fixes potassium in the soil. The leaves can also be made into a liquid fertilizer or ‘green tea’ by soaking in a bucket of water for two days.
Needless to say, we went out and got a couple of plants. And they are growing really well. We have also made our first batch of ‘tea’ and will let you know if the garden likes it.
Here’s how a green manure can help.
- The shade of dense foliage will reduce weed seed germination. Mulch also does this but green manure roots may also inhibit the growth of weed competitors.
- Beneficial soil microorganisms flourish.
- Plants absorbs available nutrients that would have been of leached out of the soil. They can now be recycled in organic form to be made available when the plants are dug in or composted.
- Plants of the Pea/Bean family often have root nodules populated by bacteria that convert nitrogen from air into useful organic nitrogen. Other green manures use an extensive root system to absorb and concentrate nutrients like potassium that may otherwise be unavailable to crops.
- The roots of green manures can increase the water holding capacity of soil to make it more drought resistant.
- Green manure roots may improve the stability of soil particles and create useful drainage channels.