May 7, 2007 at 3:00 am #239929
There have been a few threads recently on improving soil, and the best way to do this is with mature compost which contains all the chemical elements required by plants, plus humus which holds these elements where plants can use them. Humus also makes soil more water-retentive (yet better drained) and contains a host of benefical organisms that assist plants in absorbing nutrients, and others that keep soil diseases under control. Mature compost, being close to pH neutral (pH 7), also reduces alkalinity in very alkaline soils and reduces acidity in very acid soils. However, for those of us that don’t have an unlimited supply of compost, green manures are an excellent way to add much needed humus to your soil. Because the seasons are running a month or so late this year there is still time to grow green manures in temperate and warm zones.
Legumes and grains are both used to grow green manures, but the nitrogen-fixation properties of legumes are largely wasted if the seed has not been inoculted with the correct rhizobium bacterium that allows the host plant to fix nitrogen. This is because the legumes we grow as green manures originate from the Northern Hemisphere where suitable rhizobium are found naturally in soil. These bacteria won’t be found in unimproved Australian soils. Some legumes don’t do well in a mixed planting with grains but Green Harvest supply suitable inoculated legume/grain green manure mixes suitable for different seasons. Oats and Woolly Pod Vetch can be planted now, or Mung Bean and French Millet, or Cowpea and Japanese Millet can be sown in spring to summer. Green manure mixes can be ordered from http://www.greenharvest. com.au
Legumes do better in less acid soil because they also require a trace element called molybdenum to assist in nitrogen-fixation and this element is unavailable in soils with a pH lower than 6. If you have acid soils, and are keen to get started on improving your soil you can grow some grains now.
Cereal Rye (Secale), oats, triticale, wheat and barley can be sown as green manures in autumn in all but very cool areas now. Because you are only growing the plants to knee high, you don’t have to worry about incorrect temperatures or climate conditions when grains form seed.
Rye/Secale – supplies a lot of organic matter and will grow in acid or saline soils, and is good for reclaiming eroded soils. It is drought tolerant but will grow best with a bit of watering. It can also be sown in spring in cool areas.
Oats are good because they are fast, hardy and produce a lot of organic matter.
Triticale – is excellent for growing in soils that are too poor to grow wheat or barley, but will also do well in better soils. It is drought tolerant but also useful where rising water is a problem.
Wheat is good for semi-arid heavy soils. It can also be sown in spring.
Barley is drought tolerant and a good soil improver. It needs to be sown in spring or Feb/March in cool areas.
A lot of Australian soils are acidic. Although an acid soil pH is more of a problem when sowing legume green manures, reducing the soil acidity with an application of dolomite or agricultural lime (where you know soil in your area contains plenty of magnesium) before growing a green manure grain will allow you to get better results in improving soil. This is because earthworms and other beneficial organisms in soil that break down organic matter work best when the pH is close to neutral, so the break down of the green manure into humus will be slower in acid soils. Most vegetables grow best in a soil pH close to neutral and plants will be most pest and disease resistant in a suitable pH range. This is because they can obtain all the elements they require from soil to build healthy immune systems.
But don’t try to bring your soil pH to close to neutral in one go. Just give acid soil an application of dolomite/lime and select a grain that grows in acid soils. It is harder to reduce alkalinity by adding sulphur than it is to improve acid soils by adding calcium. Where soils are very alkaline, the gradual introduction of well rotted cow and horse manure, as well as compost and green manures, into the topsoil can assist in reducing soil alkalinity.
1 Preparing garden beds.
First check your soil for drainage. If soil is sodic, i.e. forms a surface crust and water does not penetrate easily, apply gypsum to an aerated soil surface, if necessary. Loosen the soil surface of the bed by rocking a garden fork backwards and forwards in the soil. This aerates the soil and will allow fertiliser, any calcium applied and water to penetrate to the root area of your crop. If you haven’t yet marked out your beds, mow or slash grass or weeds in the growing area. Do not worry about removing weeds or grass (except for couch or kikuyu) as they will form part of the soil conditioner. Kikuyu and couch should be solarised or dug out before setting up beds. Kikuyu, in particular, will always be a problem in poor acid soils. While repeated use of cultivators or ploughs will damage soil structure as well as earthworm and soil bacteria populations, compacted soil will benefit from an initial cultivation to break a hard soil surface to allow sowing of seed. Do not use herbicides to kill weeds. Herbicides, including glyphosate, can deter nitrogen fixation for up to seventeen weeks after application and inhibit mycorrhiza (a beneficial fungus).
2 Adjusting soil pH
If your soil pH is lower than 6, a dusting of dolomite/lime will be required, at least for your first green manure crop. This is extremely important if you are growing an inoculated legume. A light application of good quality dolomite for all green manure crops may also be helpful on sandy, acid soils in high rainfall areas, where synthetic fertilisers have previously been used, or when turning a lawn area into a garden. If the proposed growing area contains moss, your soil is quite acid and will definitely benefit from an application of dolomite, or agricultural lime as second choice. A handful per square metre is a good start on unimproved soil. We have found that calcium and magnesium work more quickly if dissolved in a full watering can. These products, including gypsum and fertiliser, are best applied a couple of weeks before sowing seed, but just before sowing is better than not at all.
3 Adding fertiliser
Because nutrients are not readily available in humus-poor soil, you will have to add some fertiliser to get your first green manure crop started. Ideally, fertiliser should be applied a week, or more, before sowing. Water the growing area, or apply it while soil is damp from watering in calcium. Then sprinkle an organic complete fertiliser over the growing area, and water it into the soil surface, or scratch it into damp soil with a rake. I recommend Dynamic Lifter Long life for this purpose because it is certified-organic which means the ingredients are of a very high standard, It contains chook poo, blood and bone and seaweed. A lot of blood and bone sold today contains not only blood and bone but other rubbish from abattoirs, residue from GE crops including fatty parts of animals that can affect your soil structure and moisture receptiveness. Seaweed collected from some beaches can contain industrial chemicals and/or heavy metals. Dynamic Lifter granules contain only chook poo. The cost of fertiliser applied to the green manure planting area will not be wasted, as any taken up by the green manure will be returned to the soil when the crop is cut down, and held in the humus for use by your vegetables. Where soils are very alkaline, fertiliser can be applied in the form of manure and seaweed extract teas. Scratching some well-rotted cow or horse manure through the top 5-8 cm of the soil (with a rake) will also help reduce the pH.
4 Sowing seed
To sow your green manure crop, scatter suitable seed thickly over a damp bed (between New Moon and Full Moon for faster germination), and rake lightly to cover seed. For grain seed, water the growing area again after sowing, but do not water legumes again until germination, or seed may rot. Where water is in short supply, it will help if you cover the bed lightly with fluffed-up organic mulch. To sow a large quantity of seed more evenly, divide the growing area into equal sections, and divide the seed by weight into the same number of portions, sowing one portion of seed in each section. Once seed has germinated, water only as necessary to maintain good steady growth.
5 Slashing green manure
Green manure grains are grown until knee high before cutting down. Legumes are cut down as they start to flower. Chopping up legumes after they have cropped will not produce the same benefits because legumes have their highest nitrogen content just as they start flowering, before the pods form. Spent legumes provide â€˜pea strawâ€™ for mulching. A brushcutter or whipper-snipper is perfect for the task of cutting down as plants can be chopped by removing about 10 cm of growth with each pass of the brushcutter. The green manure crop can be left to break down on the soil surface, or be turned into the top 8-10 cm of soil after it has wilted. If leaving the slashed green manure on the soil surface, leave the roots of annual grains in the ground, as decaying annual roots also add plenty of humus for the soil. Perennial legumes such as alfalfa, clover, pigeon peas, and some lupins will have to be forked out to uproot the plants, or they will keep growing and use the nitrogen themselves. Turned-in green manure can be watered and covered with a layer of organic mulch to speed up decomposition. If you keep soil just damp, the bed will be ready to use about four to six weeks after slashing, in warm conditions – a bit longer in cool weather.
Green manures are not only useful in new beds, they can be used to add organic matter to soil or provide mulch whenever you have a garden bed that is not being used (lying fallow). In areas when heavy rain can wash nutrients from soil, green manures crops are better at holding nutrients in upper layers than just allowing beds to lie fallow. Organic matter needs to replaced regularly in soil to keep it healthy. Give green manures a go. You will soon be pleased to see the improvement in your plants and soil. Don’t forget to practice crop rotation with green manures, too. Don’t always sow the same grain or legume or you can end up with some diseases through not breaking the pathogen’s reproductive cycle.
6 Using the bed
If you leave slashed green manure grains on the soil surface as mulch, you can plant directly through this when planting out seedlings. Farmers call it stubble planting or no till sowing. It is better to allow the slashed tops to brown off before planting. Because grains are annuals the plants won’t reshoot, and the roots provide a mass of humus to soil. The bacteria that break down the organic matter will require some nitrogen as they work but when the bacteria die off the nitrogen is returned to the humus and is available for your veges to use. Because most vegetables also require a good supply of nitrogen, it can help if you have to plant before the break down of the green manure is well under way if you add manure tea to the bed. (Recipe below) When planting out, pull the mulch back around each planting hole and mix some compost into the soil in the planting hole. Plant seedlings, then water thoroughly to sttle soil. Try to avoid grey water with seedlings – they don’t cope with it as well as more mature plants. Save the water that goes down the drain as your shower warms and use this.
Put a shovelful of cow or horse manure in a bucket, fill it with water, and cover it loosely (I use an old tray) to prevent the escape of nitrogen and flies laying eggs in it. If you cover it tightly the fermentation that occurs can pop the lid off. Stir it and re-cover every day or so and in about a week to 10 days, in a warm climate, you should have a good brew. Strain some of the liquid into a watering can (I line a 8 cm plant pot with a piece of old pantihose as this size fits into the top of our watering cans) and dilute the liquid to weak black tea strength, then water over the bed before planting out or sowing.May 7, 2007 at 3:11 am #300218
Thanks for your enjoyable article, I also use this method and obtain the seed mix from Green Harvest as well. The results are very good and I also supplement the Dynamic Lifter with sheep manure that I am lucky enough to be able to obtain. At the moment I have my Broccoli and Cauliflower seedlings growing in these beds and as you are aware these require alot of nutrient to perform well. Keep up the informative posts I really enoy them.
Regards-Mark.May 7, 2007 at 4:09 am #300219
Many thanks Lyn. This is a big help to me and I’m sure it will be to others who are new to green manures.:tup:May 7, 2007 at 4:18 am #300220
Thanks for putting it all together for us, Lyn. I have just followed your advice in creating 4 new garden beds in the backyard. Now all we need is some rain….May 7, 2007 at 8:15 pm #300221
Thankyou. I will be following this advice preparing the rest of my garden. Am ordering a few different types of green manure seed from Eden Seeds this week.May 7, 2007 at 8:32 pm #300222
this is great information, Lyn. Thank you. :tup:July 18, 2008 at 12:01 am #300223
I’m bumping this for Busybee and another new AlSer who needs it. 🙂July 18, 2008 at 12:19 am #300224
soil prep for spring is my next task.July 19, 2008 at 8:26 am #300225
Lyn :clap: too true! (re your line about GM foods.) Did you know that some sections of the growers community want to introduce bumblebees from Europe to Oz to pollinate greenhouse crops? As if we didn’t already have both foreign and native insects to do this!! Bumblebees are cute – but no one knows the impact they might have on our native bees and other insects. The native bee researchers are looking into using our own native bees to do the job in greenhouses to prevent this. Also, I guess that the more we grow our own seasonal(or buy local seasonal) food the less demand for commercially grown greenhouse cropsJuly 27, 2008 at 6:30 am #300226
there are bumble bees already in Tasmania. They are in NZ too (our neighbour).August 16, 2008 at 12:37 am #300227
I’m just bumping this for Emilyc – a new ALS member. 🙂January 2, 2010 at 2:37 am #300228
Hi Lyn, I pretty much have a blank canvas that I am working with as I have moved into a newly built house in a new estate and have had some good quality soil brought in to my yard, over the next few months I plan to make the beds (4-5) for my vegie garden and also plant some grass in other parts of the yard, should I grow a green manure crops in my new soil to improve the quality?
I’m also going to be mixing in some Zeolite and Olsens green bio and for the vegie beds I was going to get some composted manures to dig in before planting as well.
Thanks!January 2, 2010 at 5:10 am #300229
thanks good read! ColJanuary 3, 2010 at 5:22 am #300230
Thanks Lyn! Helpful as always!
We are new to this area and driving around we’ve seen lots of bags of manure for sale at the farm gate. How do i make sure this manure is ok for the garden? Can i just get a couple of bags and mix it in to the soil or will it need to “age”? I want to do some green manure as well so I was thinking of planting the green manure, slashing it and digging it in with some of said manure and then leaving it a few weeks before planting.
Any suggestions/comments/ideas?January 3, 2010 at 6:09 am #300231
At a talk that Frances Michaels gave at Permaculture Noosa about soil, she recommended only using Ag Lime (instead of dolomite) on soils on the Sunshine Coast as we already have very high levels of magnesium in the soil (generally speaking).
PS – we use GMCs a lot here and I always include them in my courses.
You must be logged in to reply to this topic.