Improve your soil with green manure

Green manuring is a great way to fertilise and increase the organic matter in your soil. Green manuring is an organic soil improvement method using a crop of mixed legumes and grains. The whole plants are harvested by ploughing the young plants into the soil just before they flower, investing the soil with nitrogen, organic matter and new life force.

Legumes are plants in the bean family which have a unique association of bacteria which can extract nitrogen from the atmosphere. Grains, which are types of grasses, are also used because they produce a lot of green matter quickly which on breaking down becomes soil carbon, or humus. So what we are doing here is a method of composting in-situ which can easily be done over large areas as well as backyard garden beds.

Green manure can be sown almost anytime of year but the plants used will depend on the season and your climatic zone. For seeds and information on warm and cool season green manure planting, have a look at Greenharvest or go to a stockfeed supplier if there is one in your area.

As a Winter garden is usually smaller in terms of productive plants, Autumn is a good time to sow on unused or exhausted soil to prepare it for your next Spring planting.

Here’s how to do it:

1. Clear the area of weeds and loosen soil with a garden fork.
2. Scatter seeds at two to three times the normal cropping rate.
3. Rake in seeds to protect them from birds and drying out.
4. Water until germination occurs, and then water occasionally if conditions are dry.
5. Watch for when the plants start to flower. It is then time to turn your green manure crop in. Do not allow it to set seed, as there will be less nitrogen for your soil. If you want to keep the manure growing longer to harvest more green matter you can mow it high and allow it to grow again.
6. Chop it up by mowing or slashing.
7. Spray with biodynamic cow pat pit (manure concentrate) to assist with the breakdown.
8. Allow to wilt for a few days.
9. Incorporate into the soil by digging or shallow cultivation.

The time for breakdown varies with temperature and soil moisture, but it is usually around six weeks. Check there are no lumps of rotting vegetation before planting again.

Too much digging and back-breaking for you?

An alternative no-dig method is a green manure mulch.  Simply mow or slash the green manure and use as mulch.