Homeschool Garden Club - How Can I Improve My Soil for Next Year’s Garden Club Activities?
The first thing you need to do is to identify your soil type. This counts as science, so record these activities in your evidence folder.
Knowing whether your soil type is clay, sand, silt, loam, peat or chalk will help you choose the right plants, fruits and vegetables for your garden and maintain them in good health.
There are six types of soils.
1. Clay soils are heavy, high in nutrients, wet and cold in winter and baked dry in summer
2. Sandy soils are light, dry, warm, low in nutrients and often acidic
3. Silt soils are fertile, light but moisture-retentive, and easily compacted
4. Loams are mixtures of clay, sand and silt that avoid the extremes of each type
5. Peat soils are very high in organic matter and moisture
6. Chalky soils are very alkaline and may be light or heavy
Identifying Your Soil Type
The best way to tell what type of soil you have is by touching it and rolling it in your hands.
Sandy soil has a gritty element – you can feel sand grains within it, and it falls through your fingers. It cannot be rolled to make a sausage shape. If it is not a coarse sand and perhaps a sandy loam it may stick together better
Clay soil has a smearing quality, and is sticky when wet. It is easily rolled into a long thin sausage and can be smoothed to a shiny finish by rubbing with a finger. If is it not a heavy clay it won’t get quite as shiny and be as easy to make a sausage
Pure silt soils are rare, especially in gardens. They have a slightly soapy, slippery texture, and do not clump easily
An easy science experiment to do is to test for calcium carbonate. You will need an old jam jar half filled with vinegar. Take a spoonful of your soil and put in to the jar. If the soil froths, then it contains free calcium carbonate (chalk) or limestone and is lime rich.
The next level up test will require a DIY Soil test kit from the garden centre. These kits are relatively cheap and easy to use and give a good indication of soil pH. Always follow the sampling directions given by the test kit to get a representative sample for the area in question.
It will tell you if you have acid or alkaline soil. With this knowledge, you will know the type of plants you can and can’t grow and how you manage your soil.
The soil pH is a number that describes how acid or alkaline your soil is. A pH of 7.0 is considered neutral. An acid soil has a pH value below 7.0 and above 7.0 the soil is alkaline.
When to test soil pH
It is especially worth checking soil pH before you start adding anything to the soil. So, you know what to add and how much. Now is the time to do this.
Lime is added to make it more alkaline and acidifying materials are added to decrease soil pH.
Interpreting the results of a soil pH test
A pH 7.0 is considered neutral. An acid soil has a pH value below 7.0. Above pH 7.0 the soil is alkaline.
pH 3.0 - 5.0 Very acid soil
Most plant nutrients, particularly calcium, potassium, magnesium and copper, become more soluble under very acid conditions and are easily washed away
Most phosphates are locked up and unavailable to plants below pH 5.1, although some acid tolerant plants can utilise aluminium phosphate
Acid sandy soils are often deficient in trace elements
Bacteria cannot rot organic matter below pH 4.7 resulting in fewer nutrients being available to plants
Action to Take: Add lime to raise the pH to above 5.0. The addition of lime can help break up acid clay soils.
pH 5.1 - 6.0 Acid soil
Ideal for ericaceous (lime-hating) plants such as rhododendrons, camellias and heathers
Action to Take: Add lime if other plants are grown
pH 6.1 - 7.0 Moderately acid soil
A pH 6.5 is the best general purpose pH for gardens, allowing a wide range of plants to grow, except lime-hating plants
The availability of major nutrients is at its highest and bacterial and earthworm activity is optimum at this pH
Action to Take: It is not usually necessary to add anything to improve soil pH at this level
pH 7.1 - 8.0 Alkaline soil
Phosphorus availability decreases
Iron and manganese become less available leading to lime-induced chlorosis
But an advantage of this pH level is that club root disease of the brassicas family crop is reduced
Action to Take: Sulphur, iron sulphate and other acidifying agents can sometimes be added to reduce pH. Clay soils often require very large amounts of acidifying material and soils with free chalk or lime are not usually treatable.
Manure Heaps Here We Come with Spades and Buckets!
Some plants are well adapted to growing in certain types of soil, although even these plants may struggle to cope if your soil is too compacted or too light. The best way to improve any soil type is to incorporate liberal amounts of organic matter each year.
Now we like to do things a cheaply as we can here at Orchard Training Garden Club. We have some Study Buddies with horses. We have some Study Buddies who have gardens. We have some gardens in need of horse manure both fresh and well-rotted down. Hmmm! What can we do here? Remember shifting manure is physical hard word and so counts towards you 1 hour of movement each day. Do more than an hour over the course of a week and it counts as P.E. - record it in our evidence diary.
Improving Clay Soils
Dig your soil in the autumn has come and whilst it is still relatively dry but workable. Don’t over-work your soil when digging. It is a good idea to simply lift big clods of clay to the surface so they can be broken down by frost and winter weather. Apply liberal amounts of organic matter. This could be in the form of well-rotted manure (only use fresh manure in the autumn so it can rot down over winter), or compost or recycled green waste from your local council. If the soil is workable this can be forked in, otherwise spread a 5-10cm layer of organic matter on the soil surface to be incorporated naturally by worms.
Consider making raised beds to improve drainage and prevent the need to walk on the soil. This will help prevent walking on clay soils when they are wet, as this will damage the soil structure. If you do need to access an area, try laying down wooden boards as this will spread your weight and have less impact on the soil.
Don’t add sand to a clay soil as this may make it worse. You can use gravel or coarse grit although a lot is needed to make a real difference. It’s best to just keep adding organic matter and choose suitable plants for your soil.
In the winter and spring clay soils are often too wet to be worked effectively and too hard to be worked in the summer. Use organic matter as a mulch around your plants, to prevent the soil surface drying out and cracking in hot weather.
Plant new plants in the spring as even the toughest plants may not survive a waterlogged clay soil over winter. When you do plant, make sure you break up the soil at the bottom of the planting hole first to prevent water collecting - you could even add some grit for extra drainage.
Improving Silt Soils
Spread s 5-10cm layer of organic matter that can be forked in or simply kept on the soil surface, this autumn. Silt soils are at risk from compaction so dig in some organic matter every autumn will improve the structure.
As with clay soils, try not to walk on silt soils when they are wet. Use wooden boards to spread your weight so there is less impact on the soil structure.
Improving Sandy Soils
The key to improving light sandy soils is the addition of lots of organic matter. This will bind the soil particles together and improve water and nutrient retention. Organic matter acts as a sponge and will prevent water and nutrients from being washed away so readily. This work is best carried out in both the autumn and spring
Try applying a mulch around your plants, either using a thick layer of organic matter or a layer of decorative gravel, slate chips or pebbles.
Apply mulches in early spring whilst the soil is still moist from winter rainfall.