How to improve your soil fertility: 12 things to do to have the best soil for growing healthy crops


You diligently took soil tests this winter and now they’ve come back indicating that potassium or phosphorus is low on some fields, here and there you have a zinc deficiency, and you know that you will probably need some additional nitrogen. But you’re organic! No synthetic fertilizer for you! What do you do?

Amending your soil is no substitute for good agronomic management. Fine-tuning your fertility if the agronomics are not sound is like tweaking the carburetor adjustments when there is a blown piston. Take care of the big stuff first! Adjusting soil fertility is certainly an important part of good management, but you won’t see any return from the adjustments unless your crop rotations, choice of adapted varieties, legume cover crops included frequently in the rotation, tillage, weed control, and other such factors are in line.

But, if still there are deficiencies and imbalances, there are approved products you can use (but be sure to check with your certifier before purchasing any new inputs).

Does your garden consist of lifeless or hardpan soil? While there are many ways to improve soil quality for the purpose of growing food, in this article I’ll share the methods that have been the most successful for me. Believe me, I’ve tried a lot of things!

Tilth refers to the physical condition of soil—how suitable it is for planting crops. Healthy soil with good tilth includes lots of organic matter. It is well-aerated and well-drained, yet retains enough moisture to feel like a wrung-out sponge.

To revive lifeless soil, aim to improve its tilth. One of the most important things in gardening is taking care of the soil. It is easy to forget, as we grow in our gardens, that the soil beneath our feet is teeming with life. When the soil does not thrive, plants cannot either. It’s time to stop treating soil like dirt.

Soil fertility refers to the ability of soil to sustain agricultural plant growth, that is to provide plant habitat and result in sustained and consistent yields of high quality. Here are some supplements that will boost the health of your garden.

1. Soil testing

Soil testing and fertiliser planning are key requirements for any successful farm and should be conducted during autumn in advance of fertiliser purchase.

Soil fertility is hugely influenced by soil pH, along with phosphorus (P), potassium (K) and nitrogen (N) present in the soil.

When addressing soil fertility, a soil test or analysis is key to knowing what state your soils are in. If you fail to complete a soil analysis, you’re essentially working blind when it comes to the nutrients required on your farm.

2. Addressing pH

The starting point when building soil fertility is to apply lime according to the soil test recommendations to bring pH to the target required by the crop. Soil pH has a major effect on soil nutrient availability and farmers should aim to maintain mineral soils at pH levels of 6.3; peaty soils should have a pH of 5.5-5.8.

Research from Moorepark and Johnstown Castle indicates that by increasing soil pH from 5.2 to 6.4 – and using only lime – an average grass production response of 1t/ha was achieved. This – Teagasc says – is worth €105/t. However, results of soil tests undertaken by Teagasc show that approximately 47% of soil samples from grassland farms still have below target soil pH, indicating that lime applications are required.

3. Feed it an Organic Diet

Spring brings a flurry of underground activity that we can’t see. Billions of soil organisms stretch and yawn, exploding into existence. It’s this living soil below ground that helps gardens thrive above ground by recycling nutrients, capturing water, improving soil tilth, and fighting pests and disease.

Autumn is the best season to start building your soil health. Organic materials, the key ingredients for healthy soils, abound. You can add fallen leaves, garden debris, kitchen scraps, and even apples raked from beneath fruit trees to soil.

Chop organic material directly into the top 2 inches of soil with a heavy bladed hoe and cover with mulch. Ideally, add concentrated manures, mineral phosphorous and potassium fertilizers, and lime at the same time. Adding these materials in the fall gives them time to break down for use when plants need them in the spring.

4. Implement a ‘No Dig’/ ‘No Till’ Gardening Approach

Every time we dig or till the soil, we damage the complex ecosystem below. Traditional gardening and farming involves disturbing the soil on a rather frequent basis. But in a no dig garden, we take steps to reduce disturbance of the soil as much as possible. Rather than incorporating matter into the soil ourselves – we lay material on top of the soil surface and let earth worms and other soil life do this work for us. Avoiding soil disturbance as much as possible can allow this fragile ecosystem to thrive. Over time, it will become healthier, more diverse and more resilient.

Research has shown that a no dig garden can increase the yield from a growing system over time. By avoiding soil disturbance, and through other no dig gardening methods, we can also increase the soil’s capacity to store carbon, and do our part in the fight against global warming.

5. Avoid Leaving Areas of Bare Soil

When soil is left bare, it is more likely to become degraded over time. Bare soil should therefore be avoided whenever possible when you are trying to improve the soil in your garden. Some of the ways in which we can avoid leaving areas of bare soil are listed further down in this article.

Bare soil can be:

– Eroded by rain and wind.
– Leached of nutrients, overheated or dried out by the sun.
– Waterlogged, or have its nutrients washed out by heavy rains.
– More easily compacted (especially when we are talking about heavy soils).

By making sure we cover the soil, we can keep it protected, and build it up and improve it over time.

6. Grow Nitrogen Fixers

One of the first stages in restoring degraded soil or improving soil that is particularly lacking in essential plant nutrients is introducing nitrogen fixing pioneer species. Nitrogen fixing plants co-operate with beneficial nitrogen fixing bacteria in their root rhizomes to gather atmospheric nitrogen and make it available in the soil.

Of the three essential plant nutrients – nitrogen, phosphorus and potassium – nitrogen is the most important to consider for most home gardeners. Nitrogen is one of the nutrients that is depleted most easily in garden soil. So many of our most important organic gardening practices revolve around finding ways to replenish it. While this is not the only thing to consider, adding nitrogen fixing plants is one of the most important ways to improve your soil and ensure the longevity of the system.

Gardeners should consider adding:

– Nitrogen fixing trees (like alder, laburnum or acacia, for example).
– Shrubs that fix nitrogen (like Elaeagnus, Ceanothus, or Broom, for instance).
– Herbaceous nitrogen fixers (especially legumes, such as peas, beans etc..)

Some nitrogen fixers may play their role in improving soil as companion plants or members of plant guilds. Others may be used in crop rotation (see below). Or, as you will discover later in this article, are amongst those plants which can be chopped and dropped and used as green manures or cover crops.

7. Rotate Annual Crops

Creating an effective crop rotation scheme for annual crops is one way to keep soil healthy and productive over time. If we grow the same crops in the same beds year after year, we risk depleting that soil of essential plant nutrients. By rotating certain plant families, we can ensure that fertility is maintained, and improved over time. As mentioned above, legumes are one important type of nitrogen fixing plant. This plant family will restore nitrogen to a growing area when grown within a suitable crop rotation scheme. Crop rotation can also help to prevent the build up of diseases or plant pathogens in the soil over time.

8. Apply Manure and compost-based products

Animal manures supply different amounts of nutrients depending on the animal species, feed, bedding and manure storage practices. The amounts of nutrients that become available to the plants depend on the time of year the manure is applied and how quickly it is worked into the soil. Existing soil conditions also affect how quickly the nutrients in the manure are available.On average, cow manure contains approximately 10 to 15 pounds of N, 5 to 10 pounds of phosphorous, and 10 to 12 pounds of potassium per ton. Poultry manure has a higher percentage of all three elements.The National Organic Program (NOP) is very specific about the use of manure. Composted manure is definitely preferred, but if raw manure is applied, then the timing of application is critical. Where raw manure is used on land growing crops for human consumption, it must not be applied within 120 days of harvest for a crop where the edible portion touches the soil, or 90 days of harvest where the edible portion does not touch the soil.

9. Create Permanent Garden Beds and Pathways

One rule that I learned early in my garden training is to never walk in garden beds. Stepping on garden soil compacts it, which destroys tilth as well as beneficial soil organisms and their habitat. Establish permanent beds and walkways so that the beds are clearly defined. Keep them narrow enough that you can reach all areas without stepping inside to keep foot traffic out. Beds created in this way can improve each year rather than starting each season in a compacted state from last year’s walkways. In addition to keeping soil in the garden beds loose, permanent beds also save time and money.

Rather than applying costly amendments over a broad area, you need only apply them to permanent bed areas, skipping the pathways. Irrigation installation is easier, too, since the beds are permanent fixtures. Permanent pathways of white clover, microclover, or wood chips attract beneficial insects and fertilize the garden.

10. Mulch for Big Benefits

Mulching encourages healthy soil tilth by retaining moisture and nutrients. It also saves time by reducing the need for weeding, watering, and fertilizing. How you mulch your garden beds depends on your climate. For example, heavier mulches are beneficial in hot, dry climates where moisture evaporation is high. In contrast, lighter mulches are more appropriate in cool, rainy climates where soil benefits from the warmth of the sun, but still needs protection against erosion.

For most gardeners, a heavy mulch in the off season provides protection beneficial soil organisms against the elements and reduces soil erosion from heavy rains. After a pest outbreak, however, discard affected plant material and do not apply mulch over the winter so as not to provide protection to overwintering pests.

11. Plant Cover Crops

Cover crops are an excellent addition to your soil improvement program. They can provide organic matter and nutrients, improve drainage and aeration, attract beneficial soil organisms, and act as an overwintering mulch.

While cover crops can be grown in rotation with other crops at any time throughout the year, they are most popularly sown in the late summer or early fall to grow over the winter. Many are killed by the winter cold to make spring planting easy, while others are turned under before planting. Use a digging fork (or chickens!) to turn cover crops under about three weeks before planting in the spring.

Here are some cover crops that have worked well for me:

– Buckwheat
– Cowpeas
– Daikon Radish

12. Use Organic Liquid Fertilizers

Mulching and other methods mentioned above improve soils slowly, over time. But to improve soil fertility in a more immediate way, and benefit individual plants, you can also consider using liquid fertilizers. Liquid fertilizers can quickly replenish certain missing nutrients in the soil, and redress nutritional deficits in your plants.

Rabbit urine makes an excellent liquid fertilizer as well as an awesome insecticide. Just dilute the rabbit urine with water using a ratio of 1:5 where 1 is the portion of rabbit urine and 5 is the portion of water.