Growing a Green Manure for Summer

Summer green manures for naturally fertile soil

A green manure is a crop of seasonal plants that cover your soil protecting it from drying out and erosion. At the same time, the green manure is growing leaves and roots that when dug in, will add organic matter and nutrients to your soil.

Adding nitrogen, the building block for growth. If you grow a green manure that is a legume such as those in the pea and bean families, they will also capture atmospheric nitrogen and via the work of rhizobium bacteria in the roots of the plants, will convert atmospheric nitrogen to plant available soil nitrogen. It’s like an application of free manure to your soil.

How are green manures different?

I grow a green manure crop in my vegie garden plots about once every 12 months. I just sow a block at a time so I can keep on growing other vegies elsewhere in the garden. They are annuals that grow and are dug in within about 3-4 months, giving a quick turn around.

Dig them in before flowering to add valuable organic matter and nutrients to the soil. If you want to eat your soy beans or peanuts, dig them in after you have harvested.

Green manures for subtropical summers

(Choose 1 or 2)

• Peanuts (Shown in the picture as little seedlings a month old
• Soy beans (Beans are edible too)
• French Millet (Looks like grass)
• Mung beans (Yes, you can harvest and sprout the mung beans!)
• Cow peas (These trail or climb and the bean-like pod can be eaten)

How to do it?

1. Pull back any mulch on the garden bed.
2. Get out your 2 or 3 pronged cultivator and scratch around in the area you’d like to plant, loosening the soil.
3. Mix your seed in with an inoculant if supplied. Add the inoculant to a little milk to make it wet then add the seed, mixing well. (Each nitrogen fixing seed has a particular rhizobium inoculant to help it fix even more nitrogen from the atmosphere. An inoculant is not essential.) Sprinkle some dolomite or lime into the inoculated seed and mix. Just enough o make the seed dry again and easy to sow.
4. Throw the seed over the prepared bed and rake with a metal rake or the cultivator to cover with soil.
5. Water well to moisten the seed and soil.
6. It won’t be long before they shoot through the soil and you can watch your ‘fertiliser’ grow. How easy is that!

As the crop of green manure starts to flower, chop up the plants with a spade and fork them into the soil. You’ll be ready to plant your vegies a week or two later once the leaves of the green manure have died away.