I am preparing my raised beds for some early spring sowing. I put in some manure a few months ago. Over the last year or so the beds have really settled down and so there is plenty of room to add more to them.
I was wondering if it is better to add pure compost or topsoil or a mix of both. Does pure compost have all the nutrients a vegetable needs, and do the nutrients last very long, or is topsoil longer lasting? Also, what is a "soil improver"?
My soil is tending towards to clay side of things.
The inorganic portion of your soil (85%-90%) is roughly, 20 - 30% clay,
30 - 50% silt, 30 - 50% sand. The organic content is 5 - 10%.
Clay is good for soil, as it retains water and plant nutients, but too muck clay will prevent penetration of water into the soil.
To break up clay soils, I'd recommend a cover crop of rye or buckwheat. I have problems with daylight because I live on the north side of a hill and I am just starting to get some full sunlight into my beds. Rye improved my beds amazingly last year. This year I've sown rye and buckwheat, earlier than last year, and the buckwheat is performing better than the rye, so far.
I add chicken manure (18 lbs/100 sq.ft.), rock phosphate, charcoal, and whatever else I intend to add to the beds, and then cover the cover crops (cut or not) with newsprint two weeks before I'm ready to plant (sometime in May), and mulch over the newsprint with alfalfa (lucerne).
This is "no dig" gardening.
Tillage of soil releases a flush of nutrients, which can give an impressive initial boost to crop growth. But this surge of available nutrients results mostly from the death of large numbers of soil organisms, whose biomass decomposes rapidly into the soil. These nutrients tend to be in soluble and volatile forms, and if not taken up immediately by plant roots, are leached to groundwater or outgassed to the atmosphere. In the meantime, life cycles of many soil species are disrupted ? fungal threads are broken, and earthworm burrows are destroyed ? and it can be some time before their populations recover. If the next tillage occurs before they have done so, we have started a cycle which degrades the health and diversity of the soil food web. One of the worst effects of excess tillage is the loss of carbon bound in the soil in the form of humus. Oxygen is necessary to soil life, which is a major reason we work to improve aeration in soil through creation of looser, more open ³pore structure.² Excessive exposure of the soil to oxygen, however, as occurs in heavy tillage, leads to oxidation of the carbon content and its loss to the atmosphere as carbon dioxide (CO?). Not only is fertility ? which is so dependent on humus content ? impaired, but high-tillage agriculture is a major, and growing, cause of accumulation of CO?, a greenhouse gas, in the atmosphere.
One cautionary note though, beware chemical fertilizers. This doesn't come from ridged ideology but from the facts that numero-uno: chemical fertilizers, used at suggested rates, kill off soil organisms, which leads to less top soil, which leads to the use of more chemferts to maintain production, and numero-two-o: the translocation of the nitrogen to the plants now rapidly growing leaves (nitrogen rich, tender leaves) makes them a target for garden insects.
Take advantage of your local library and read:
Teaming with Microbes: A Gardener's Guide to the Soil Food Web Jeff Lowenfels and Wayne Lewis
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Omnivore's Dilemma: A Natural History of Four Meals by Michael Pollan
It depends on the composition of what is there and how much you need to add. If what is there is still heavy, tends to set hard and has low organic matter add compost or manure. If it is friable and has good organic matter but needs to be topped up quite a bit add topsoil or topsoil and compost/manure. If it just needs a bit add compost/manure.
Whether pure compost has all the nutrients depends on its sources, it is possible that it does but it is not certain. A compost made from just one source probably is not complete. The time that the nutrients in any soil last depends on the situation. The one thing that you can say about gardening that is almost always true is "it depends".
This is a vry complex subject so I am skimming here. Nutrients do not last long if they are lost quickly to the environment. The main method of loss is running off when dissolved in water but evaporation can play a role too. Run off happens more when nutients are present as very soluble compounds or ions and when the soil has little capacity to bind them. Binding takes place on the surface of colloids which are found in clays and in broken down organic matter. It is not the source of the nutrients that determines how long they last but the environment that they are in.
What you should be aiming for is balance in tilth and infiltration, and retention of water and nutrients. Very sandy soil has little binding power, pouring on chemferts will have only a short term effect, most of it will end up in the nearest waterway helping the water plants to grow. Heavy clay has much binding power but it is so impervious that there is no room for air and plant roots and it takes ages for water and nutrients to infiltrate. A soil that has a balance of clay, sand and organic matter is workable and can carry nutrients, air and water. Such soil allows water to infiltrate and to drain away reasonably quickly but holds some.
"anthony123hopki" wrote in message news: snipped-for-privacy@gardenbanter.co.uk...
use whatever you have. Nicely broken down and crumbly compost is fine. Top soil is good. If you have both. mix them together and use. There is no exact science as far as I am aware. The manure you set down should supply a decent amount of nutrients. Compost or topsoil will have other nutrients. The key is to keep on adding every year of so composted manure or compost to keep nutrient levels up. What you have sounds fine. If things do not work out do some investigation then to determine what the problem may be.
A soil improver is basically organic matter is whatever form (compost, manure, leaf mould etc) that is worked in to the soil to 'improve' the soil. That is, a soil rich with decayed organic matter is better than a soil with little decayed organic matter.
I have a heap of organic matter ibn my raised gardens andn it works for me. I obsessed for a couple of years about putting it in to the soil. Having seen that things work ok without my obsession, I just add the inputs & let the plants get on with growing.
I'm the same way. I just throw whatever I have available at any particular time of year--whether that be old leaves, fresh grass clippings, pulled weeds, or kitchen scraps--into the beds and let nature work it out. I do pretty well that way.
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