How to improve your soil

By Val Bourne

Read gardening expert Val Bourne on ways you can improve your soil with tips on mulching, manure, compost and more.
SoilThere are many ways you can improve your soil, such as adding compost and mulching

Improving the soil involves two aspects - firstly adding more nutrients and secondly adding humus (organic material like garden compost or manure) to improve the structure.

Adding organic material makes the soil airier and this aids root development and tends to improve drainage on heavy soil. Once the organic material breaks down, after a year or so, the process may need repeating.

The main consideration is your soil. Those on heavy clay may wish to follow the Great Dixter method of adding coarse grit to heavy clay to improve drainage.

Adding grit has the advantage of being permanent and clay is already a fertile medium. Once the digging is done it would then be possible to top dress with a sprinkling of a slow-release fertiliser like blood, fish and bone every March and September.

Read our guide to improving clay soil.

Many plants, including most silvers and tap-rooted plants like eryngiums and verbascums, prefer a poorer diet. So soil improving needs to be targeted in certain areas - where vegetables are to be grown, or where moisture-loving plants like phlox are to be planted. 

Make your own compost heap

Making your own compost heap is the first step to good soil, within six months you will have your own free, friable soil improver. Making your own compost can provide a great source of nutrients for your garden as well as using up leftover food and garden waste.

Read our guide to making a compost heap for more information.

Double digging (for manure and compost)

Double digging involves removing one spit (or a spade's depth) of soil. The bottom of the trench is then roughly dug over with a fork to break it up to improve drainage.

At this stage garden compost or manure can be incorporated into the trench and covered with the remaining soil to make a raised fertile mound. This is perfect for legumes (like peas and beans) and you can even fill one of these trenches with vegetable waste and leave it over winter.

Buying in manure

Animal manure  can be a problem

I am old enough to remember that when a horse went down a London street everyone would rush out with a bucket and shovel to collect the precious muck.

One horse apparently produces between 1600 and 1800 pounds per year and in Susan Campbell’s The History of Kitchen Gardening she describes the perfect diet for a horse kept for its manure. It’s quite a thought. But these days most horses are bedded out on woodchippings rather than straw and this makes their manure less user friendly.

A modern problem - aminopyralid

Animal manure has recently caused great problems for gardeners because some batches have contained a chemical that kills crops and many gardeners have had problems in the few years.

The problem has been linked to a new herbicide called aminopyralid (a hormone weed killer) being used on grassland by the farmers. The animals either feed on the grass, or ingest silage during the winter months.

The residues come out in the manure. The most sensitive crops affected are tomatoes, peas, beans, carrots, potatoes and lettuce.

Many farmers now buy in fodder and they may not know whether it’s been treated or not. But manure from cows and horses, once so valued by the vegetable gardener, is now to be viewed cautiously. For this reason I have stopped buying in manure, but it has made my compost heaps even more necessary.

Apparently a good way to tell if the manure is fine is to buy a tomato plant and repot it using some of the manure.

Green garden waste

Councils all across the country now have green waste collection schemes and they sell their compost. Schemes vary because many councils sell it straight to a commercial compost company. Others seem to sell their own.

Ring you council offices to find out their system. If you can buy it cheaply you will be able to dig this straight in without fear of unwanted seedlings.


Mulching is double-edged sword when it comes to improving the soil because the decomposition process uses up nitrogen on the soil surface - robbing the ground of nutrients.

The way round this is to use a nitrogen feed (like chicken pellets or powdered 6X chicken manure) before you apply your mulch of bark.

The other golden rule is to always mulch wet, warm soil to trap moisture. Mulching on dry soil prevents rain penetrating the ground.

Read our guide to mulching to save moisture.

Feeding your soil

Slow-release fertilisers are much better at releasing nutrients in the best way. Blood, fish and bone is generally the best and the powder is easy to spread.

There are water-based fertilisers that deliver a fast rush of nitrogen and they promote a lot of soft leaf. This soft growth is unattractive to look at and more prone to pets attack - it’s almost a gourmet meal for aphids. It could be used on brassicas, but isn’t suitable for strawberries in flower.

If you want to promote flower and fruit opt for a tomato feed or make your own comfrey tea.

Read our guide to making comfrey tea.

Subscribe to our free weekly newsletter for more great gardening tips and growing guides every week.


  • Helenium 'Sahin's Early Flowerer' dazzles in shades of orange

    How to improve clay soil

    Read gardening expert Val Bourne on the best ways of improving clay soil in your garden.

    Read on

  • Compost heap

    How to make a compost heap

    Read gardening expert Val Bourne on how to make a compost heap and how to use compost from both hot and cold heaps.

    Read on

  • Comfrey

    How to make comfrey tea

    Find out how you can use comfrey plants to make comfrey tea - a free organic fertiliser that's perfect for promoting fruit and flower growth and improving the soil.

    Read on

  • Barry Wenborn

    Posted: Wednesday 03 September 2014

    I have a problem with my soil, the drainage is too quick, eg. if it rains one day, the next day the soil is dry.
    Also the soil itself seems very light an crumbly.
    How can I make the soil more heavy so as to perhaps retain more water because plants that are in the soil do not show much growth.
    Thankyou Barry


Type your comment here

 characters remaining.

Saga Magazine

£3 for 3 issues

For more fascinating stories and insightful articles, why not try Saga Magazine for just £3 for 3 issues.

How to fit a water butt

It makes sense to save and recycle rain water by installing a water butt in your garden. Not only will you be doing your bit to ease the pressure on our reservoirs and underground aquifers, but you could even save money if you are hooked up to a water meter. Martyn Cox tells us how it's done

Top 50 over-50 bloggers

There are now around 180 million people writing internet blogs commenting on anything from politics to polenta, from sex to socks. And age is no barrier. Here’s our pick of the best, from the fingertips of bloggers over 50...

Saga Dating

The over 50s dating website from Saga

  • Create your dating profile in less than 5 minutes
  • Our unique two-way matching process will help you find your perfect partner
  • Protected by the Online Dating Association

Get two pre-planted hanging baskets for just £19.99

Plus free delivery and free hydrator

Get two pre-planted Petunia 'Magica' hanging baskets for masses of cascading pink, purple, pink bicolour and white flowers.

More gardening articles

Browse our extensive archive for more gardening news and advice from our gardening experts.