With almost all of my tree planting over, I’ve been getting the vegetable growing areas ready. Normally I would be doing this in Autumn, but I wanted to get the trees in first, and then the snow interrupted that, and so it is only now that I’m catching up on my work. In the interim, I’ve been catching up on my reading/research. So I’ll explain what I’m doing at the moment, and some of the different vegetable growing systems that I’ve been trying to incorporate into a coherent single ‘way’ for me to garden.
Most of my beds are raised, without frames/sides, about 4 ft wide, and orientated North to South.
My Autumn preparations involve hand weeding the beds, but leaving the roots of any ‘good’ plants in the soil. I then add Rockdust’ to the surface of the beds. This is followed by the addition of crushed charcoal (biochar), and compost, or leaf mould for the root vegetable beds. The beds are then covered with a loose mulch of straw, to protect the surface, and give a covering for the microbes and soil life. All of this is very deliberate. Three of the elements which have the highest Cation Exchange Capacity are clay, humus, and charcoal, so by adding compost and charcoal to my clay soil, I am maximising it’s ability to provide minerals to my plants, and byadding the Rockdust I am trying to ensure that any minerals that may be deficient are available. In the Spring, the straw on the beds is removed, in order to allow the soil to warm up more quickly. The straw is mixed with the first grass clippings of the year and composted.
Vegetable Growing Systems
Like many people, I operate a minimal dig system, with raised beds. The advantages of the raised beds is that they give deeper access for roots, particularly in compacted/clay soils, like mine. However the same effect can be created by double digging, such as that advocated by John Jeavons in his biointensive method. The trouble with any form of digging is that the extra aeration that it gives, allows the soil microbes to consume the organic matter in the soil more quickly. Repeated disturbance of the soil also destroys mycorrhizal fungi. This sounds pretty bad, but most of our commonly grown vegetables prefer a mixed bacterial/fungal mix in the soil, and most brassicas don’t asssociate with fungi at all. So if you add enough compost to more than replace that which is being lost when you dig, you may end up improving the quality of your soil. Although I wouldn’t dig at all if my soil was less compacted.
Like most systems that rely on beds, the biointensive system uses a close spacing of plants. One of the reasons for this is that they say that closely spaced plants shade the soil, which reduces water loss through evaporation. This is one of my main problems in the Summer. The raised beds improve drainage when the soil is wet, but we have dry Summers, and that means that I need to water more. This is compounded by the fact that the beds are also losing water from the sides as well. Some of my recent reading is making me think hard about whether to contine with using raised beds. The first is reading ‘Gardening when it Counts’ by Steve Solomon’. He claims that planting too closely reduces the area that the roots of each plant have to search for water, and that a wider spacing leads to increased yields. He controls moisture loss by using a hoe to create a loose layer of dry soil on the surface, which reduces evaporation by preventing the upward movement of soil water by capilliary action. Now this contradicts the biointensive view, and has led me to reconsider how I plant. The second is reading an article by another blogger. In his post on Pit and Mound Gardening, Onestraw talks about creating mulched trenches in his paths to improve drainage and water retention. If you look at his post, and see the paths thickly mulched with straw, that’s what I’m doing at the moment. I’m hoping that filling the space between the beds will reduce the moisture loss from the sides of the beds, and the paths, and retain water, as well as reducing weeding.
Having done that, I’ve been thinking more about what I’m actually doing, because the overall effect of what I’ve done is to create a level surface, about a foot higher than the normal level of the soil. This should make a very productive bed, but I cannot help thinking that I could have achieved the same result by double digging, and incorporating large amounts of compost.
For now, I’m going to see how things work out with the deeply mulched paths, but once the straw in the paths starts to break down, I’m considering digging it in as deeply as possible, and incorporating as much leaf mould and woody material as I can (the woody stuff lasts much longer). This will improve the overall structure of my compacted paths to at least two feet below the current level of the top of my beds. Then I will shift the topsoil from the current raised beds onto the space where the paths are now, without inverting the soil, to create new beds, with a considerably deeper root run, but with the soil life at the same depth as it was before beginning. I will then dig organic matter into the new paths, and deep mulch them with straw. What I hope to achieve is to gain the benefits of deep digging, but by keeping the frequency of digging down to a minimum, reduce the damage to the soil microbes.
Sustainability and Vegetable Growing
At the moment I’m buying the straw from a local farm, which may not be sustainable in the future, so I will need to provide my own mulch. This may be wood prunings, but is one of the uses that I have planned for the bamboo that I have planted. As for the cost, I can mulch all of my paths for about what I earn for two hours of beekeeping. This will save hours of weeding, and possibly of watering too.
If you haven’t already come across it, I would recommend How to Grow More Vegetables, by John Jeavons. The detail, and research is exemplary, as is the realisation that to maintain soil fertility, a high proportion of what we grow has to yield biomass to return to the soil. He has also produced a DVD, which I have ordered, and will review once I have seen it. The Steve Solomon book, Gardening when it Counts, is also worth reading as an alternative Vegetable Growing Book.