Tips and tricks

Keep your garden healthy with Green Manure

Keep your garden healthy with Green Manure

If you are not rotating your crops every year then the future of your soil quality could be in BIG DANGER!

If you plant the same variety year after year in the same place, your soil will become deficient in nutrients, encouraging pests and diseases to become prevalent. The consequence for you? Not being able to grow again in that area of your garden!

So why does this occur? Certain crops and plant varieties demand different nutrients from the soil. If you plant the same crop time and time again in the same spot, these crops will be sapping all the same nutrients from the soil, allowing no time for it to recover or replenish. Eventually the nutrients will run out.

This phenomenon has been experienced in the Great Plains of America where farmers kept cropping in the same paddocks year in and year out without allowing the soil to rest and recover. Over time the soil structure broke down, nutrients were severely depleted, leaving nothing but a great big dust bowl!
As much as it needs to happen for huge growers, even in your back garden you need to be rotating your crops to rest the soil and allow it time to replenish its natural nutrient levels.

We recommend the ‘one in three’ principle whereby you do not grow the same crop in the same place more than once in every three years. Instead allow a fallow period, plant a green manure crop which can be turned over before flowering. An autumn grain, peas, broad beans, vetch or mustard are all excellent crops to replenish the soil with humus. By doing this, your soil will be arable for a longer term.

We suggest even drawing a simple map of your garden to plan the rotation of your crops to ensure that you keep on top of this potential problem and to give you peace of mind that your garden’s soil is going to be ok!


When your summer vegetable garden has done its bit and you have nothing planned for your garden space but to leave it fallow – SOW A GREEN MANURE CROP and add to your garden’s health in the following ways:
  • Improves soil fertility
  • When dug in, adds nutritious elements to your soil
  • Increasing levels of beneficial fungi & bacteria
  • Broken down plant material adds humus (water holding component)
  • Prevents soil from drying out, can hold moisture longer
  • Breaks up/aerates soil allowing more microbes/insects in
  • Stops erosion by sun (panning/caking), wind (topsoil blown away) and rain (topsoil washed away)
  • Control weeds by occupying spare space in your garden
  • Controls pests in the soil  - for example nematodes (see note below)
  • Sow Green Manure Crops (GMC) into freshly tilled ground.
  • BEFORE FLOWERING (or at least before the plant has gone to seed), mow the crop, allowing the plant matter to dry out before you hoe (or dig) it in.
  • This process takes around 60 days.

NOTE:  Avoid allowing the crop to go to seed as the GMC will then become a weed in your garden!

  • Don’t sow the same species as green manure – for example – after growing a brassica crop like cabbage, don’t follow it with a brassica GMC like mustard or radish.  Choose an unrelated species like Phacelia instead.
  • For a Nitrogen Fixer choose from the following legumes – Broad Bean, Crimson Clover, Lucerne, Lupin & Pea (in Kings Green Manure Mix with Oats) or Soybean
Best choice for all year round as it is vigorous
Frost hardy in most areas for most of the year and may even handle a light sprinkling of snow
Provides huge amount of green material that breaks down quickly
Contains two legumes – Pea and Lupin
Oats provide green matter, lots of fibre and carbon

  • Phacelia – germinates at a low temperature, establishes quickly and can be sown right up until late April and again from September onwards.
  • Buckwheat - not related to any other species so can be sown after any other crop; frost sensitive so can be sown for a limited time only – late October/November through to March; will be ready to hoe in 30-35 days; great source of phosphate.
  • Mixed Grain Carbon Crop – includes Wheat and Oats which are frost hardy (Barley is not frost hardy though), can be harvested as a stock fodder.  Not good if bird or rodent problem exists – great source of food for them!
  • Mustard – is a brassica so shouldn’t be sown where other brassica have just been grown, has a fumigant effect on the soil and will kill bad bugs BUT also good bugs.
  • Daikon Radish – unique effect, breaks up soil deeply when roots are hoed into a crop but also releases a sterilizing gas (methyl bromide), use where you have a problem insect that needs “blasting”.
NEMATODE CONTROL – Sowing Marigold in your garden will help control nematodes in the soil.  This happens ONLY in the root zone of the Marigold plant where ozone is released causing the nematode egg to mature through its life cycle without reproducing.  Numbers of nematodes can be reduced by up to 99% in this way.  These soil borne insects can attack the roots of plants leading to a secondary infection which ultimately becomes visible in a plant’s leaves.

Oh dear!

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