Organic farming: Soil preparation is the first step


By Digital team | 20 May 2019
soil
Photo: Theuns Botha

Anybody can grow vegetables organically, says grower Jane Griffiths, but it’s important to start out right. We asked her why soil preparation is so important.

Good soil preparation and soil health are the foundation of successful organic farming. “A crop is a mirror of the soil it grows in,” says Jane. “If the soil is very depleted, the crop could struggle to grow and produce good yields.”

HOW SOON CAN YOU PLANT?

This depends on the soil type and condition. Loamy soil is ideal, but it doesn’t mean that severely depleted, sandy or clay soil can’t be improved. Adding organic matter to sandy soil and sand to clay can improve soil quality and water retention. Over time, the soil will revert to its original state, so continuous soil building is necessary.

Jane advocates a “no dig” policy as this encourages the soil’s natural ecosystem to establish itself. Once the lower layers of soil are fertile, you need only to add compost and other organic matter to the surface to maintain fertility. Over time, earthworms and other soil organisms will pull these down into the soil, aerating and enriching it in the process.

When you are preparing beds, however, you do need to dig to enrich the lower soil layers. This is the only time deep digging is needed. The first step is to remove the topsoil layer and set it aside. Dig down and set aside a further 20 cm to 30 cm of soil. Using a fork, loosen the hard soil at the bottom of the hole. Don’t turn this earth; just loosen it. Add a layer of compost and well-rotted manure about 20cm deep before filling in the hole and returning the topsoil.

If you are following the “no dig” method you should never stand on the soil, as it will become compacted. If this happens, there are no air pockets in the soil and plants will have to struggle to get to nutrients.

Jane says it’s easier to prepare and maintain the soil if the beds are not too big. A good rule of thumb is to establish beds that are roughly the size of a door.

WHY SMALL BEDS?

Smaller beds are more manageable. “You should always be able to reach right into the centre of the bed,” she says. This makes harvesting and compost distribution much easier. It’s also a good idea to make pathways between the beds for easy access.

Cover the pathways with straw or pebbles to prevent their becoming muddy. If you prefer to make slightly bigger beds, place a few stepping-stones or planks in the bed to avoid compacting the soil.

Before Jane started farming, she drew up a plan for the layout of the beds. She has a mixture of circular and rectan¬gular beds.

Most beds should be in an area that receives full sun, as vegetables need at least six hours of sunlight every day.

COST-EFFECTIVE SOIL PREPARATION

One of the major advantages of organic farming is that input costs are much lower; even soil preparation need not be expensive. Instead of buying expensive fertilisers, start a compost heap, or buy ready-made compost.

This will help you start soil preparation and planting more quickly, but it will also add to the start-up costs.

“If you don’t have the money to buy compost, make it yourself. In the meantime, you can get on with the beds and constructing pathways,” she says.

WHAT CAN BE USED TO MAKE COMPOST?

The only materials that cannot be added to a compost heap are dairy products, cooked or baked items (such as bread), and cat, dog or human faeces.

  • Pig manure can be added, but it it’s very strong and cannot be used as a vegetable fertiliser for at least 6 to 8 months.
  • Sheep manure can be used, but the only disadvantage is that the droppings have to be collected.
  • The compost contents must be left to rot completely before being used as fertiliser.
  • Any garden waste can be added, but it is important to include an equal mix of brown and green waste.
  • For example, if too much grass is added, the compost heap will become slimy.
  • Balance out the grass with twigs and dry leaves.
  • Build a compost heap on the ground, not on plastic sheeting or in a drum or bin.
  • The reason for this, says Jane, is that compost-activating organisms must be able to move freely from the ground into the compost heap.
  • If it rains, cover the heap to keep it hot.

EARTHWORMS

“You need many earthworms because they’re incredibly beneficial,” Jane says.
Earthworm castings leave the soil 8 times more enriched than compost only. If the compost heap is healthy, earthworms inhabit it naturally. You can also farm worms and collect the castings.

Jane points out that farmed worms are different from those that occur naturally in the soil. They’re called red wrigglers and are much smaller than ordinary garden earthworms. Red wrigglers must be kept in a separate earthworm bin.

Pre-made bins are sold for this purpose, but it’s possible to make your own. Earthworms don’t like light, so use a black plastic bin or other container. Punch holes into it for drainage and aeration.

You also need a plastic tray to place under the bin to collect liquid. Add fresh vegetable waste to the bin every few weeks, but ensure that the vegetables are not too acidic. Once the worms have digested the waste, tip the bin onto a black plastic bag covered with netting. The worms will crawl towards the bag and the castings will remain behind on the netting.

Jane says you can scatter the castings onto the bed, but it would be more useful to place a small quantity in seedling holes before planting. Seedlings need extra-nourished soil and the castings are ideal for this purpose.

TIPS

  • Buy ready-made compost from a reputable supplier, otherwise you could find the compost contains too many weeds.
  • Jane encourages all organic farmers and gardeners to keep a garden diary to track how the crops are performing.
  • Include information such as where seeds have been planted, when they germinated, flowering times, successes and failures.
  • Include a sketch of each bed layout in the diary. As you add more beds, it can be difficult to remember what has been planted in which bed.

Also read: How to go organic – the basics

  • This article was written by Wilma den Hartigh and first appeared in Farming SA.