Organic Gardening

Grow Organic

Choosing the right soil and fertiliser for organic crops


On behalf of, and with our thanks to Keith Higgins

Freelance writer

Beautiful potato flowers on the allotment


Now we come to one of the most important aspects for creating your growing space – the soil and fertilisers. At the end of the day, the make-up of your soil will make or break your organic produce, so it holds a crucial role. Soil will have an impact on aeration, drainage and water holding capacity.

There are four components making up the soil of your choice:

  • Rocks and minerals

  • Organic matter

  • Water

  • Air

What you need now are the percentages of each in soil to determine the quality. Of course, it’s this quality that’ll factor whether your plants will be able to grow and flourish. For instance, soil of 25% air, 25% water, 40% mineral matter and 10% organic matter would be close to ideal. Typically, soil of this nature would be dark coloured, smell sweet and mostly be full of worms.

If you’re an experienced gardener, you’ll know the soil is crucial to the development of your plants. To continue improving the quality of your soil, add plenty of organic compost on a regular occasion.


• Preparing garden soil

This is where you really need to put the groundwork in (excuse the pun). If you’re to undertake organic gardening of any form you need a good base and this is where preparing your soil is crucial. As such, any soil needs to be well fed – as this is what’ll in turn be feeding your plants. By maintaining a healthy soil you’ll promote excellent plant growth that can better resist disease and insects. You’ll need to test your soil’s pH to know what you’ll feed it – as this will highlight the nutrients that are short in supply. You should carry one of these tests out every two or three years and kits can often be purchased from your local garden store.

• Adding organic matter

It’s not just a basic layer of soil you’ll want in your garden. In fact, adding organic matter will be hugely important and improves the structure, texture and aeration of the soil. Also, organic matter can help the soil maintain a neutral pH level throughout the year, whilst offering precious nutrients to your organic plants too. By adding organic matter, you should consider this an investment in your soil. Whilst you won’t witness instant results, it’s something that’ll pay off over the year and in the long run. Not only will organic matter improve the overall structure, but also bring useful nutrients that your plants love.

• Checking the soil pH

As briefly mentioned above, the pH level of your soil plays an important role in how well your plants will grow. Dependent on the acidity or alkalinity of your soil, this will impact what nutrients are available for plants to feed off. The pH scale ranges from 0-14, with those less than 7 considered acidic. For your organic fruit and vegetables to grow well, you’ll want a pH value between 5.8 and 6.8. At this level, roots are able to absorb and process nutrients. In order to correct the pH level of your soil you simply add the opposite to its compound.

To improve acidic soil to give it a more neutral value, gardeners tend to add lime particles – This is known as liming. Different soil types will require a different amount of lime and you can checkout a limestone calculator to analyse this. Wood ash has also been known to raise the pH levels, but can breakdown quickly – so you need to ensure not misbalancing the soil.

If on the other hand you want to decrease the soil’s pH value, you’ll need to source acidic material. For those with organic gardening close to their hearts, elemental sulfur is commonly used. However, the conversion rate differs from soil to soil and will depend largely on factors such as the soil moisture, temperature and bacteria. For this reason, in some cases it can take a number of months for the pH value to be drastically affected. Again, checkout a sulfur calculator to determine how much is required.

As a side note, it’s worth noting you shouldn’t look to alter the pH value of your soil by more than 1 unit annually.



Growing organically
The Complete Guide to Growing Your Own Organic Food - Chapter 4
Allotment websites
Allotment websites