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Beginner’s Guide to Vegetable Gardening – Part 2, How to Prepare the Soil

digging in soil with garden spade

Preparing the Soil for Growing Food

The secret to successful food gardening is rich, healthy soil. What goes into the soil goes into the food coming out of it! Plants take mineral nutrients and water from the soil, along with carbon dioxide from the air and sunlight from the sun to feed themselves and produce food for us.

How do you rejuvenate a neglected garden bed?

  1. Weed the garden bed if it’s filled with grass and other unwanted plants.
  2. Restore soil fertility by digging in manure, this acts as a slow-release fertiliser which provides plants with the food they need food to grow.
  3. Restore soil structure by digging in compost, as plants grow better when they can easily push their roots through loose , friable soil, and water soaks through the soil much more easily to reach plant roots.

Choosing the Right Fertiliser for Food Gardening

Manures – I like to use organic cow manure, it’s cheap and works well. I avoid sheep manure because it tends to contain weed seeds and fills the garden with weeds. Please be aware that all manures which are sold at garden centres are composted. Don’t use fresh manures in your garden as they’re too strong and can burn plant roots.

Balanced slow-release fertilisers – Many other fertilisers can be purchased to be used to feed your garden, always use slow-release balanced fertilisers which come as pellets, prills, or powders.

Liquid fertilisers – Don’t use liquid fertilisers as the main feed for the garden, they’re just used as a quick additional supplemental feed to use in the weeks after feeding with proper fertiliser, and just wash away.

Organic fertilisers – It’s a good idea to use natural or organic fertilisers, because the synthetic chemical fertilisers tend to force-feed plants, making them soft, sappy and weak, which makes them more vulnerable to pest attack. Also, what you put into your soil goes into your food and into your body!

For more information on feeding the garden and choosing the best fertilisers, see the article Understanding Fertilisers – How and when to feed your garden.

To Dig or Not to Dig?

Don’t like digging? There is no need to dig and turn all the soil over to plant a garden, that’s a really inefficient and unsustainable traditional practice carried over from large scale farming, it ruins the soil by killing all the beneficial microorganisms (critters) in the soil which plants depend upon to grow. Many gardeners avoid the back-breaking work of digging these days by using the technique known as No-dig Gardening, or Lasagna Gardening in the US.

How to Fix Common Soil Problems

Compacted soil – dig in some compost to improve soil structure and drainage. How much compost should you add? Mix in the proportions of 25% compost to 75% soil. If you add too much compost, the garden will sink down in soil level as the compost breaks down. If you add less compost, it still helps, so add what you have! You only need to dig in compost to a depth of 30cm (1’) as most vegetables are very shallow-rooted, with 80% of their roots in the first 30cm of soil.

Sandy soil – dig in some compost to improve moisture and nutrient retention. Once again, use proportions of 25% compost to 75% soil.

Clay soil – dig in some compost to improve drainage. Once again, use proportions of 25% compost to 75% soil. Gypsum can also be used to break up clay soils, it works by causing dispersed clay to clump, but organic matter must be added in addition to gypsum because organic matter needs to be incorporated between the clay particles to improve the soil. Without the organic matter, gypsum just created clumped clay, which is not soil!

Be aware that gypsum only can break up sodic (sodium-containing) clay soils, it doesn’t work on calcium-rich clay soils at all.

The simple way to test clay soil is to place a small soil sample in a shallow dish filled with water. Leave it there for 10-30 minutes to test clay dispersion in water. Calcium clays don’t disperse, whereas sodic clays disperse strongly, as shown below. The water around the edges of dispersive soil samples will be cloudy and milky-looking due to dispersed clay.

Dispersion test in dish of water of clay soils that are non-sodic to highly sodic (from left to right)

How to Improve Water and Nutrient Retention in Soils

Digging organic matter such as compost and manure into the soil helps with moisture retention, but most organic matter eventually breaks down and needs replacing.

During drought conditions and heatwaves, soils tend to lose moisture easily, so a once-off solution is very helpful. One permanent way to improve soil moisture retention it to add the following soil amendments:

Zeolite is a naturally occurring mineral with a porous crystalline structure and an incredibly high surface area, allowing it to hold up to 60% of its weight in water. It also binds nutrients and slowly releases them, making fertiliser last longer, and prevents nutrients washing out of the soil.

Biochar is a highly porous soil amendment material which similarly increases water retention and reduces fertiliser leaching.

Both zeolite and biochar work indefinitely and don’t need to be replaced. These soil amendment materials are a much better option than many synthetic soil wetting agents which only act for a short time before losing effectiveness, and are nothing more than detergents which are bad for the soil.

Compost Mass Production Made Easy

It should be evident by now that the way to build good productive soil is to add lots of organic matter to it, and a really easy way to do that is to add compost to the soil.

In a food emergency, large areas of garden need to be prepared quickly to commence food production ASAP. A good amount of high quality compost can radically transform sub-standard soil into a rich growing medium overnight. Traditional slow composting is not viable for generating compost for situations such as this because it can take weeks or months, and the quantity of organic material is insufficient due to loss of volume, as the compost that is finally produced is only 20% or 1/5 of the volume of original ingredients.

To put it another way, with slow composting, a cubic metre of materials only yields 200L of compost after a lengthy wait, and the final product may contain weed seeds and pathogens (plant diseases) which may contaminate a new garden!

There’s a far better solution though… It’s possible to make compost in 18 days which is of a much higher quality, which is weed-free and pathogen-free, with no volume loss, so one cubic metre of materials will produce in cubic metre of compost! Please follow this link to learn how to make compost in 18 days using the Berkeley hot composting method.

Smart Water Planning

Some plants such as herbs , which are fairly close to wild plants, can get by with very little water, fruit trees need a bit more water but not too much, while most vegies, which have shallow roots, need lots of water.

Consider that many Mediterranean culinary herbs such as rosemary, thyme, oregano, marjoram, sage and savory love hot, dry conditions, and if there is a location that might be too harsh for vegetables, it might make an ideal place for a herb garden.

When planning what goes into each garden bed, it’s best to keep all the plants that need lots of water together, that way you can heavily water the garden beds that need the most water, and not waste water on too many garden beds where it’s not needed.

Grouping plants by water requirements not only helps save water, but also prevents overwatering those plants which don’t like too much water and can get root rot if the soil becomes too wet.

How Big Should a Garden Bed Be?

Don’t make garden beds so large that you have to stand inside them to garden. There should be paths around garden beds designed for people to stand on and access all parts of a garden bed. People have no place standing in garden beds, treading on the soil just compacts it, destroying soil structure. Plants don’t grow very well in compacted soil because they can’t push their roots through the soil very easily to seek out water and nutrients, and water doesn’t soak into compacted soil very well to reach the plant roots.

Ideally a garden bed should be no more than 1.2m (4‘) wide if it’s accessed from both sides, as this width allows an adult to reach just past the centre from any side, giving optimum accessibility to the gardening area.

What is a garden is against a a wall or fence? A garden bed should be no more than 60cm (2’) wide if it’s accessed from one side only, which is half of the width of a bed that can be accessed from both sides.

For more information on the best sizing of garden beds, including garden beds for children, see the article – Raised Garden Beds – What Size is Best?

Garden bed ergonomics, if you can’t reach past the middle, it’s too deep, and you’ll end up standing in the garden bed to use all the space available!

Planning a Garden, Start Small and Build Repeatable Units

Starting a new garden should be a manageable task, so start with a single garden bed, get that working right, then build more of the same, replicating the first successful implementation.

If you have a large site, plan where the garden beds will go, where fruit trees will go, and whether you want separate herb garden beds and vegetable garden beds to save water.

Some gardeners make the mistake of building too many garden beds all at once, and find that they can’t manage them all. To avoid this problem, after you’ve built your first garden bed, add one or two extra garden beds at a time, and continue doing so until you either have enough garden beds that you can manage, or you can’t manage any more.

Once the garden beds are built, the next step is to sow seeds or plant seedlings, as discussed in the next article – Part 3, Sowing Seeds and Planting Seedlings at The Right Time of the Year.

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