top of page
  • AttractaRoach


Now is the right time to grow green manure crops. So what are they? And why are they good for the garden?

Green manures are generally fast growing crops like oats, wheat, fava beans and field peas that are allowed to grow and then slashed as the plants begin to flower, while still green and lush. It is a great way to prepare your vegie patch for Spring/Summer, particularly if you plan to grow heavy feeders. Green manure (also known as green composting) acts like compost in many ways, but it has a few additional benefits that compost doesn’t have:

  • Improves Nitrogen in the soil, as well as potassium, magnesium, phosphorous and sulphur.

  • Introduces organic matter and microbes.

  • Breaks disease and pest cycles.

  • Weed control, by preventing weeds from getting a hold or smothering those that try to grow.

  • Prevents soil erosion and leaching.

  • Improves moisture retention.

  • While growing, the green manure crops provide a habitat for beneficial insects.

  • Used in crop rotation to improve the soil.

  • Rejuvenates old and tired soil.

Select the right plants

You need to select the right plants suitable to your climate and soil. Usually a legume combined with a grass is a good combination, as this provides nitrogen from the legume and organic matter from the fibrous grass. Green manure can be grown in both cold and warm seasons, but the selection of seed will depend on the germination requirements, the time of year and the temperature.

In cool climates and winter

Grow things like fava bean, fenugreek, lupins, subclover, oats and woolly pod vetch. In cool climates (cold winters) it is advised to start planting in March, but if the area is generally frost-free these seeds can be sown right through winter, until early August.

In warm climates or warmer seasons

Grow crops of cowpea, mung bean, soybean, French white millet, buckwheat and Japanese millet. In tropical areas, seeds can be sown throughout the year as long as water is plentiful. For the more southern states sow in spring once frost has passed, usually mid-September. You can continue to sow in summer when good rainfall is expected.

How to sow

First, correct any nutrient deficiencies (except nitrogen) before sowing. Legumes prefer a neutral soil, pH 6.5 - 7.5. Scatter the seed evenly across freshly cultivated ground and lightly covered or raked in. Read the individual packets for instructions. In most cases allow a minimum of 8 weeks for the green manure to grow.

When to harvest

Never let the crop to fully flower as this will reduce the nitrogen content and increases the chance of seeding, which will become a problem for your next crop by becoming a weed. Always harvest just as it is about to flower. You harvest two options – you can slash or dig in.

Slashing method

By slashing you are leaving the green manure crop on top creating a mulch for the following crops. The nutrient breakdown is slower, which helps with retaining nutrients over a longer period (it is not washed away because of rain). If you are planning to grow your vegies sooner, slashing is the quicker method of green composting.

Dig in Method

It makes it easier to incorporate the green manure crop into the soil if you slash or mow it beforehand. Then dig it into 15cm of topsoil. Unlike the slashing method, green manure will break down rapidly, but you need to be aware that biofumigation occurs (the composting process within the soil), which can prevent seeds from germinating. Therefore, it is advised not to grow your next crop until at least 6 weeks have passed and the green manure has decomposed completely.

Green manures are a great way of improving the soil condition, reducing weed growth, allows the roots of your vegies to grow deeper and stronger and makes your plants more disease and pest resistant. If you are serious about being sustainable, organic and biodynamic in your garden, you need to consider green composting.

I hope this has helped you understand green composting and encourages you to give it ago. Feel free to ask questions or to give some suggestions. We want to hear from you.

Be earthly passionate gardening,

Attracta & the earthly passion team

26 views0 comments
bottom of page