Green manures are a handy method of soil revitalisation to add to your permaculture repertoire. Here Bruce tells how he used it on the worn out soil of his greenhouse.
by Bruce Hedge
Newham, Victoria.
The winter was not given to us for no purpose. We must thaw its cold with our genialness. We are asked to find out and appropriate all the nutrients it yields. If it is a cold and hard season, its fruit, no doubt, is the more concentrated and nutty.
— Henry David Thoreau
Maybe it’s just that I’m a year older, but this winter seems colder than any I’ve experienced in the twenty-nine years we’ve been at ‘Wirreanda’ in Central Victoria. The firewood supply cut from the woodlot in spring last year is diminishing rapidly, and each time I go down to the greenhouse to collect a barrow load, I’m reminded how wonderful greenhouses really are. I use an end of one of our hoop style poly houses to dry the wood over summer, and then plant crops in the part where the wood was, alternating each year. This gives the soil underneath a chance to rest after the onslaught of the tomato crop from the previous season, but I’ve recently noticed something that catches up with all of us after a few years of planting in intensive areas. The soil is wearing out. It doesn’t get rained on. It gets baked hard in summer. It gets thrashed with close cropping. And it’s starting to say to me “I’d like a rest, or a little bit of food!” The structure is not good. And even with a really good soaking, the worms don’t reappear readily, and they, of course, are the best indicators of soil fertility there is.
The obvious solution is to incorporate huge quantities of organic matter, the best of which is compost, but most of us don’t make the large amount necessary to replace what we take out of the soil. We can mulch the prunings from tagasaste or similar living haystacks but it’s a big job to get enough to spread over the whole garden, and you have to own or hire a suitable machine for the purpose.
Feed the soil, not the plant
 The foundation of permaculture is sustainability. One of my early memories was a saying from my grandfather: “Feed the soil, not the plant”. I’ve read that numerous times in many books since, and it is so true. In our permacultures, in addition to the perennial fruit trees, most of us have annual gardens to provide the conventional vegetables we eat every day. There’s something not quite right about bringing in material from outside to continue our quest for food. That’s where the magic bullet of green manure is such an important part of annual gardens. At the beginning, it is necessary to incorporate minerals to correct severe soil deficiencies, and to raise the pH to acceptable levels, but once a satisfactory level is reached, (around pH 5.5–7) continual input of organic matter by the use of green manure crops should keep the garden sweet. Green manure is simply a crop of legumes, grasses, or clover planted to be either dug in, or cut and left to smother weeds on the surface.
The major advantages of green manure crops are that they:
- increase organic matter, earthworms and beneficial micro-organisms;
- increase the soil’s available nitrogen and moisture retention;
- stabilise the soil to prevent erosion;
- bring deep minerals to the surface and break up hardpans;
- provide habitat, nectar and pollen for beneficial insects and reduce populations of pests;
- improve water, root and air penetration in the soil; and
- smother weeds.
Some people recommend inoculating legumes before planting your green manure crop, but if you pull up the roots of your broad beans, you may find tiny white nitrogen nodules on the root hairs of plants which have not been inoculated. Really all we want to do is get more organic matter into the soil, and to loosen up the structure. I have used buckwheat as a terrific green crop, but it is very frost tender, and should be planted in late spring, or early summer. Seed can be obtained quite cheaply from health food shops, or the Middle East grocery shops and a little goes a long way. Run a mower over the metre-high growth when the white flowers are out, shredding the stalks into a fine mulch. As the stalks start decomposing, they may initially rob the soil of nitrogen, but I’ve found that if you plant brassicas for winter straight into the mulched area, and water with a nitrogen-rich fertiliser like comfrey manure, they’ll take off! If I’m not feeling that pure, I’ll use a seaweed solution to give some trace elements to the soil. Weeds are suppressed, and the roots of the buckwheat wither away, opening up the soil, allowing worms to do their wonderful work! Worm manure is full of nitrogen, and eventually the soil becomes good enough to eat. Well, almost!
Green manure plants
Many different plants have been recommended for green manuring. Depending on the season, and your climate, you might choose from mustard, barley, wheat, ryecorn, lucerne, tickbeans, lupins and vetch. Oats are said to release phosphorus the following year. Your local feed merchant will have the seeds, and the cheapest way to start is to grab a kilo of field peas and dig or rotary hoe them into the top five centimeters, and let ‘em fly! That’s what I’ve done in the greenhouse.
The disadvantage of all this is, of course, that the land may be growing a crop which will not be harvested for food. Never mind, the soil is benefiting greatly from your inputs. Remember—feed the soil, not the plant. Next year’s crop will be much better.
Of course, you’re all growing a comfrey patch, aren’t you? Slashed leaves are a wonderful mulch. I have to warn you though, that placing a tightly packed onion bag of comfrey leaves into a drum of water, and allowing it to rot down for comfrey manure, produces the most foul smelling liquid. Don’t get it on your clothes or hands. You have been warned!
Comments to bahedge@bigpond.com
Hemp Wool - a Natural For Knitters
New Hemp Wool 8-ply and 20-ply yarns have been released by the enterprising Nundle Woollen Mill (phone (02) 6769 3330 or order online at www.nundle.com). The mill staff experimented with blending Chinese hemp and 23-micron pure wool earlier this year and 50 per cent hemp and 50 per cent wool 8-ply yarn, and 30 per cent hemp and 70 per cent wool 20-ply yarn are now in full production. The 8-ply is available in 100g balls and the 20-ply is also sold in 200g hanks at the mill shop at Nundle. People have responded enthusiastically to the yarn and are curious to know how it feels and of course asking the predictable “Can you smoke it?” The answer is no, industrial hemp containing untraceable amounts of THC, the active ingredient in marijuana.
Hemp has long been held in high esteem for its qualities including durability, coolness and environmental sustainability. Hemp is the longest and strongest natural plant fibre, can be grown in most climates, requires little or no use of fertilisers, insecticides, fungicides or herbicides and has a deep taproot, raising nutrients to the soil surface.
The Nundle Woollen Mill hemp wool blend was made on machinery ranging from 50 to nearly 100-years-old, so the mill team was unsure if or how the hemp would perform. Nundle Woollen Mill proprietor, Judy Howarth, said she was delighted with how the machinery handled blending the fibres, the softness of the yarn (comparable to a wool/linen blend), and how it was knitting up.
“One of our Nundle knitters, Mary Little, has hand knitted samples of a cable patterned beanie, scarf and fingerless gloves using hemp wool, while Amanda Ducker of Minx Handknits used hemp wool in a tea cosy, egg warmers, and dolls,” Judy said. “The yarn is working really well across a range of garments and homewares, which shows its versatility for a variety of knitting projects. It will be sold undyed so knitters have the choice of dyeing it themselves, combining it with coloured yarn, or using it in its natural colour, which is a lovely warm earthy tone.”
What's Your Problem?
Bob Rich answers questions about owner building
Contact Bob with your queries about building by e-mail: bobrichATweb.solutions.net.au. Or write to Bob Rich, c/- Earth Garden, PO Box 2, Trentham, 3458, Victoria. Please enclose a stamped, self-addressed envelope. For readers who don't want their question published, please enclose $20 with your question.
Loadbearing strawbale walls
Hi Bob,
My partner Trev and I LOVE your book.
We’re currently doing rounds with the engineer and drafter trying to nut out a final plan for our strawbale home to be.
We want to build without the use of concrete, so we are sinking celery-top pine piers down to rock and building a pole frame house on the stumps.
We wish to build strawbales to the roof. However, the engineer wishes to build in articulation joints by going to just above door level and adding a timber or mini orb infill. To our minds that makes strawbale walls merely a token gesture. We’d like to build to the roof line and run poles/door frames/window frames to the roof.
The engineer is concerned about cracking. We keep assuring him that we would expect minor cracking for a number of years.
I’ve attached an image of the side of the house with bales detailed. The northern wall now has one set of double doors less than in the image.
Very grateful for any answer received.
Linda.
Dear Linda,
Of course, you realise I am neither an engineer nor an architect. I am not competent at carrying out calculations. But then, strawbale houses are rather different, and I suspect many professionals go by the seat of the pants too. And when they do, they need to avoid failure. Signing a plan that results in an unsafe building lays them open to being sued. A building that is over-engineered, costs more than it should, or fails to meet the dreams of the owner does not result in successful legal action. This is why, if they don’t know, they naturally go for putting in extra.
What we can do is to look at what works elsewhere.
You already have a copy of my book. Incidentally, if you send me a self-addressed envelope with an unused fifty cent stamp inside (to cover my stationery expenses), I’ll send you a signed book plate to stick into it. And as the owner of one of my books, you qualify for a free one (in electronic format). Go to http://bobswriting.com/bookbuy.html and make your choice. You might be interested in the reissue of my other practical book, Woodworking for Idiots Like Me.
However, you didn’t write which version of the book you have. If it’s the newest (fourth) edition, you will have the chapter on strawbale by John Glassford. He will approve of your planned footings, although some of his footing designs will probably be cheaper. If you have an earlier edition, borrow the fourth from the public library to read this chapter. Show it to your architect and engineer too. John’s ideas are based on meticulous research, and a lot of personal experience. They work.
You might also have a look at Practical Strawbale Building by Murray Hollis. It is published by CSIRO Publishing, so your professionals will respect it. You can read my review of this book at http://mudsmith.net/bobbing5-4.html#murray.
Both these sources emphasise that loadbearing strawbale walls are sound. It seems to me that the design concept in your drawings is fine. I see no reason for either horizontal or vertical timber loadbearing members to break the structure up.
However, the engineer is also right. You need something to keep the wall rigid. This is achieved by compressing it, using fencing wire. Once this is done, there should be only minimal movement. Both Murray and John give detailed instructions on how to do this.
Good luck with your project. I’ll be interested to know how it turns out.
Bob.
Shredded paper insulation
Hi,
I am doing a science project on which insulators work best and I have come to the conclusion that shredded paper is the best. I haven’t been able to find any information on reasons why this may be so. So...why is shredded paper a good insulator?
Thank you, Tamara.
Dear Tamara,
The first thing about shredded paper is that it needs to be made fire and rot safe, and rodents need to be discouraged from making a home in it. This is usually achieved by soaking it in the mix people used to apply to thatch for roofing. This mix is borax, boracic acid and a few other substances.
I don’t know that shredded paper is ‘the best’. This depends entirely on how much you use. You see, bulk insulation works in the same way clothes do to keep you warm: they trap a layer of unmoving air. It is actually the air that does the insulation. So, if you have a certain thickness of trapped air, it does the same amount of insulating, regardless of what traps it. This could be fibreglass or rockwool batts, sheep’s wool, shredded paper, stacks of boxes, whatever.
In fact, shredded paper and other loose fill insulation materials have a disadvantage in that they are likely to compact over time. A 100 mm-thick batt will stay 100 mm thick, while 100 mm of shredded paper is likely to reduce significantly in thickness after a few years. This of course reduces the amount of trapped air, and therefore insulating quality.
However, there is a big advantage to shredded paper over conventional batts. This is the ‘embedded energy’, or ‘energy of manufacture’. Glass melts at 1300 degrees Celsius. Rockwool is basically artificially generated lava that is formed into fibres. So, the manufacture of these materials takes up huge amounts of energy. In contrast, shredded paper, straw and sheep’s wool are waste materials, and need very little processing to make them useable.
Hope that answers your question, and good luck with your assignment.
Bob.
Bob Rich has been writing for Earth Garden for longer than any other contributor, apart from Keith Smith, the magazine’s founding publisher. These two are the authors of the popular Earth Garden Building Book, now in its fourth edition.
Bob has other titles as well. His second book was Woodworking for Idiots Like Me, a series of amusing stories that teach woodcraft as well. This was in print between 1994 and 1999. It is now out again in a different format. In effect, it’s a large web page. This gives it many advantages over a paper book: it doesn’t eat trees; it costs half as much (even less if you count the cost of postage); you can view it at varying magnifications (every e-book can be a large print); and you can jump about within it using hyperlinks.
What’s more, if you buy a copy, Bob will give you a second electronic book free.
To see this marvel of modern technology, have a look at www.mudsmith.net/woodcont.html.
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