Frequently Asked Questions


  1. Delivery and Postage
  2. Process and Kit
  3. Questions about Contamination
  4. Soil Fertility

What does the fertility data mean?

This is a complex question and a bit of a rabbit hole which can go very deep indeed. Essentially the soils main fertility parameters are nitrogen (N), Phosphorous (P) and potassium (K). Most over the counter fertilisers show an N-P-K ratio of what is contained. This is usually shown as 5-5-5 or 10-10-10 which means the N-P-K ratio is equal, although the 10-10-10 is twice as powerful as the 5-5-5 so in theory half the amount would be required in normal circumstances to achieve the same fertility rate as the 5-5-5 ratio.

What the Fertile Soil results show is the actual current concentration of those nutrients in your soil sample. It is possible that the ratio is not equal, and therefore getting a fertiliser with a different ratio to balance the soil's nutrition may achieve best results. This may involve some calculations and consideration but probably worth it!

In addition to the main parameters (N-P-K) there are other major elements (calcium (Ca), magnesium (Mg), sulphur (S)) and trace elements of which there are many. Some of these are included in the Safe Soil and Fertile Soil suites to give indicators of the soil make up which may show deficiencies in things certain plants require for growth or will grow better with. Each plant is slightly different and each garden and allotment will need different things so one size will not fit all.

The following websites are useful in understanding the soil elements and what they do for your plants. Also, they go into a bit more depth on the ratios that you may wish to understand.

A small note to help your calculations, the nitrogen (N) content in the Fertile Soil results is displayed in % whereas the phosphorous (P) and potassium (K) are shown in mg/l. To convert the N from % to mg/l to make the ratios more easily comparable every 1% of nitrogen (N) is 10,000mg/l, every 0.1% is 1,000mg/kg. This is based on an assumed liquid weight of water.

What should I grow in my soil based on the results?

The short answer is what do you want to grow? Most plants and vegetables are quite resilient and will grow in most soils but there are obviously some plants, such as acid-loving Azalea's, that will not thrive in certain soils.

It will be worth looking into the specific things you would like to grow and work back from that. Some shrubs, trees and perennials prefer specific conditions, based on the 'right plant, right place' ethos i.e., a plant will grow best in the conditions in which it is naturally found.

Woodland plants, such as ferns, like to grow in soil rich in humus, where they would naturally have leaves breaking down on the surface, whilst many herbs come from the Mediterranean and are happiest growing in soils lower in fertility and very well-drained to mimic sunbaked hillsides.

The effect of soil texture

The soil texture will also have an effect as well as the fertility parameters you have. Chalky soils tend to be alkaline whereas woodland floors tend to be more acidic.

The following website may be of use to determine the soil texture:

As a general rule of thumb, plants will thrive in a soil that provides the conditions closest to its natural habitat, be that through its soil composition, fertility or light levels.

Chalky soils are alkaline and often very well-drained so suit several drought-tolerant shrubs and perennials. They also tend to be low in nutrients and suit sun-loving plants such as Ceanothus, Lavender, Hardy Geraniums and Cistus. a list of different locations and garden styles preferable to certain plants.

Deciding on pH for Shrub / Perennial / Groundcover sub-categories

pH - where most plants will thrive in neutral (pH7) soil, some plants are better suited to acidic soil, which has a pH range below 7, in which certain nutrients are easily washed away.

If the pH is highly acidic (3.0 - 5.0) you are best to add lime to allow most plants to survive. Plants that can cope with acidic soils around 5.1 - 6.0 pH include Camellia’s, Rhododendrons, Heathers and Blueberries.

Soils that have a pH of over 7 are more suited to a larger number of plants, so for a good all round planting scheme you should aim to get your soil to a pH around or just above 7.0.

Certain vegetables such as Cabbages actually prefer alkaline soils as they prevent certain diseases, so veg growers often add lime to their growing beds. a list of different locations and garden styles preferable to certain plants.

Plants for Polluted areas

Some plants can cope better than others with life on the roadside. Pollution and dust can clog the pores, but you should also consider water run-off and soil erosion in these areas. Plants will have to cope with vehicle emissions, salt-spray in winter and a range of weathers and temperatures.

Choose plants that are tough and not too ornamental - they need to be easy to maintain and quick to recover but the positive side is that you are creating green zones in a harsh environment, both visually and for wildlife.

RHS (Royal Horticultural Society) researchers have found that Cotoneaster Franchetti is a shrub that effectively soaks up air pollution alongside roads whilst the classic London Plane tree (Platanus x Hispanic) also does well in polluted areas.

Buddleia is considered a weed in many areas as it can grow practically anywhere, even up through cracks in pavements, so this can be used in roadside areas and a bonus is it’s loved by butterflies, hence being known as the Butterfly Bush.

Other pollutant-tolerant plants include climbing honeysuckle, and berberis, which has the added bonus of being a super-spiky shrub so makes a great burglar-deterrent hedge!

Traditionally foraged plants such as Wild Garlic, shouldn’t be taken from beside roadsides as the pores will have taken in harmful pollutants. The same applies to roadside blackberries, apples and elderflower. The phrase 'you are what you eat' should be applied here when you consider where our edibles have been before you enjoy them. Provides a list of plants happy to grow in contaminated soil that may even assist in cleaning the soil over time.

Specific Advice for Planting in Your Garden

At Soil Check we know a lot about contamination and fertility, but we do not know everything about plants. We have teamed up with a Gardeners World Researcher and all-round gardening genius Natalie Ashbee who has helped us with planting advice. If you would like specific advice on what would work well in your garden, we would suggest you contact Natalie at

Phytotoxic Metals and What they Mean

In addition to what you would like to grow and what the fertility and texture are like, it may be worth looking at the results from the Safe Soil to see if there are any phytotoxic metals which mean plants may not grow or will struggle to grow. Note that these numbers are based on studies for agriculture and forestry so the actual distress garden plants and vegetables may show, at or above, these levels is unlikely to be severe but should numbers be significantly higher than those in the table and plants are struggling to grow, the level of the metal / metalloid in the table may be the issue.

 pH Range of Soil
Metal/ Metalloids in SoilpH 5-6pH 7pH >7
Chromium (III) 400400400
Chromium (VI) 252525