More than any other factor, the fertility of your soil will impact the success of your crops. Whether you live in a new suburb or on a farm, you may encounter infertile soil – and whatever is causing the soil infertility needs to be addressed before you can expect the maximum yield from your crops.
Soil infertility can be due to physical or chemical issues in the soil, and will require you to improve either the physical structure or the balance of naturally occurring elements in the soil – or both – to increase soil fertility, and improve the health of your soil.
No matter how poor the soil might be when you begin preparing your soil, with enough patience and effort, you can create a healthy, fertile soil.
How can I make my soil more fertile?
Creating healthy, fertile soil is not difficult when you understand its basic components. Soil is essentially composed of weathered rocks and organic matter, with air and water mixed in.
Balancing the elements will allow the true ‘magic’ to happen – the organisms (insects, worms, small animals, and microbes) that bring life to your garden will increase the soil fertility and your crops will flourish.
About half of the soil particles are small pieces of weathered rock that have naturally eroded into one of three types: sand (large particles), silt (medium-sized particles), or clay (tiny particles). This determines the texture of your soil and affects its drainage and nutrient content.
A simple soil test will allow you to determine the type of soil in your planting beds, and whether you need to improve the soil structure.
As the particles are large, a sandy soil contains so much air that microbes consume organic matter very quickly and nutrients will drain away rapidly with the water, before the plants can absorb them.
To improve sandy soil, work in 8-10 cm of organic matter such as compost or well-rotted manure; you will need to add at least 5 cm of new organic matter every year.
Mulching around your plants with leaves, wood chips, bark or stray will help to retain moisture and cool the soil. You can also grow cover crops or green manures.
The small, flat clay particles will pack together so tightly that they leave little space for air to circulate. When wet, clay soils are sticky and virtually unworkable; they also drain slowly and will remain waterlogged until well into the spring, often becoming hard and cracked as they dry out.
The lack of pore space reduces the level of organic matter and microbial activity in the soil; while it is rich in minerals, clay soil can often become so compacted that plant roots will be stunted when trying to push through it.
To improve clay soil, work 5-8 cm of organic matter into the soil in the fall, then continue to add at least 2 cm of organic matter every year. Using raised beds or drills will also improve drainage and keep foot traffic out of the growing area, preventing compaction; try to minimize tilling and spading clay soils.
While a pure silt soil tends to be more fertile than either sandy or clay soils, its small, irregularly shaped particles can be dense and have small pore spaces, which leads to poor drainage.
To improve silty soil, simply add 2-3 cm of organic matter every year and avoid compaction by not walking on or tilling the garden beds unnecessarily.
Though only making up 5-10% of the soil, organic matter is essential; the partially decomposed remains of organisms and plant life bind the soil particles into porous granules – basically soil crumbs – allowing air and moisture to move through the soil. More importantly, organic matter feeds the microorganisms.
Adding animal manures, green manures (also called cover crops), mulches or peat moss to the soil will increase the organic matter content; try to avoid high-carbon materials such as straw, leaves, wood chips or sawdust as soil microorganisms consume lots of nitrogen while breaking these materials down, which may deprive your plants of nitrogen.
The best type of soil
The best type of soil – the one you should aim for is a LOAM.
This is a balanced mix of clay, sand, silt and organic matter. This will perform the best in terms of body, texture, drainage and the ability to sustain a higher pH (from 6 to 7).
What is soil
Healthy soil will contain about 25% water and 25% air. Soil organisms – the bacteria, microbes, insects and small animals that are essential for plant growth – require that much air to live; however, too much air can cause organic matter to decompose too quickly.
Like air, water is also held in the pore spaces between soil particles; the ideal soil will have a mixture of large and small particles, allowing the nutrient-enriched water to drain at the proper pace while being absorbed as needed by plant roots.
A pH test will determine the level of acidity or alkalinity of your soil. A perfectly neutral pH level is 7; however, most essential plant nutrients are soluble at between 6.5 and 6.8.
If the pH of your soil is much higher or lower, plant health will suffer; while you can’t – and shouldn’t – change the pH level overnight, it can gradually be altered over one or two growing seasons and maintained thereafter.
To raise the pH level and decrease acidity, you can add powdered limestone to your soil in the fall; wood ash works more quickly than limestone but it contains potassium and other trace elements which can cause nutrient imbalances.
If your soil is too alkaline, you can incorporate ground sulfur or naturally acidic organic materials such as conifer needles, sawdust, peat moss, or oak leaves.
The best way to determine the nutrient levels in your planting beds is to have a soil sample analysed.
Soil tests typically rate the levels of soil pH, phosphorus, potassium, magnesium, calcium and sometimes nitrogen (though it’s rather unstable in the soil and tests don’t always reflect the true nitrogen levels).
Some labs may also verify other micronutrients such as boron, zinc, or manganese.
Spring and fall are the best times for soil testing; you should obtain samples from each garden area: lawn, flower garden, vegetable garden, or even the soil surrounding fruit trees.
With the results in hand, you can choose the appropriate synthetic or organic fertilizers to optimize your soil fertility. It can be a long road to get your soil fertility optimal but it will be a very rewarding one.