Green manuring is the organic process of growing plants and digging them into the soil when they are still soft and sappy. This biomass is dug in like a manure to provide plant nutrients and carbon.
Explaining Clever Clover
The process of growing biomass to dig into the soil and decompose, (which raises organic carbon levels), has been refined one step further with CSIRO’s development of the legume Clever Clover. As the CSIRO says:
“Legumes use nitrogen from the air, convert it to plant protein and eventually release it to the soil in a form that the vegetable crops can use.”
Clever Clover are legumes that grow through the cold, wet weather, and being annual, die back in late spring, just in time for the planting of tomatoes and other summer crops. Not only does it provide nutrients for your garden beds, it dies down and forms a mulch in time for the planting of summer vegetables. The dying roots provide valuable air pores for the roots of summer vegetables to grow into, creating a soil aeration without the harmful effects of digging. It saves on weeding, digging and spreading fertilizers provided the timing is right. If, for example, the subterranean clover does not die down when you want to plant out tomato seedlings or pumpkin seeds, simply solarise the clover by covering the area with clear plastic (25°C+ temperature) which will effectively burn off the foliage and roots without affecting the soil.
When to sow in garden beds
In autumn sow in rows with 20cm between rows at about 5 seeds per 2.5cm.
In late spring Clever Clover dies down and in late summer/autumn the seeds of Clever Clover germinate to continue the cycle.
Comfrey
In a climate as dry as Australia it is vital to grow those deep-rooted plants that mine the soil for water and nutrients during those summer months when plant survival is threatened. Two plants stand out – alfalfa lucerne and comfrey.
Comfrey will out-produce even alfalfa yielding up to 100 tons of organic matter per acre.
(UC Davis, California). Its nitrogen content is so high it can replace manures when making garden compost. It is used by poultry farmers to improve laying and the colour of egg yolks, and the strength of eggshells. Its leaves are a rich source of potassium, nitrogen, silica and iron. It grows quickly and it is so tough that it can be cut with a lawn mower and collected with the bag attachment up to 4 times a year.
Growing your own lucerne hay
The CSIRO has developed a complementary system whereby a deep-rooted, summer-active perennial legume can be grown alongside rows of vegetables or fruit trees to harvest water deep down and provide a highly nutritious biomass that can be cut to be spread as a mulch. Alfalfa lucerne was chosen because its roots can grow as deep as four metres and it provides biomass for our fruit or vegetable cropping systems. In their trials the lucerne was planted in alley’s where our access paths are. It was not watered and only occupied 50% of the area, but it still produced six tonnes of hay/hectare that contained 20 grams of nitrogen, 105 grams of phosphorus and 20 grams of potassium per square metre, which is enough to support any vegetable crop.
Clever Clover Kit for Sale
For a fertile, weed-free garden, this clever kit developed by the CSIRO contains 4 seed packets to create the healthiest well-mulched garden around. Sow mustard in autumn, which acts as a biofumigant and then dig in as green manure. Sow also the two clover varieties, which will die down in late spring to make the perfect weed free bed for summer vegetables. Sow the lucerne in spring to fix nitrogen and draw up nutrients in tired soil, then cut for mulch.
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