Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden. More on Tony O’Neill
Many gardeners cannot get the best yield from their plants or notice they have to take care of their garden more than might be necessary. So they spend more time in the garden, may have to water more often, and might take a few other steps. The answer may be a soil fix.
There are several ways to ensure your soil is fertile enough to experience great productivity from adding organic materials like manure, compost, and mulching. Adding a few necessary critters that form part of soil life gives the soil adequate water and air.
In the long run, the success of your garden depends on making healthy garden soil. The more you can do to keep your soil healthy, the more productive your garden will be, making for a higher quality of your crops and greater yield.
Soil, Composition, and Fertility
Before we talk about fertility, we have to understand the soil itself. This is because, while every soil may be improved, knowing your soil will determine how much improvement may be needed. The soil is composed of various materials, but generally, soil composition means the proportion of sand, silt, clay, and humus in the soil.
There are four major soil types, and their features include:
- the exact opposite of clay soil
- particles are large and do not bind together
- it is the warmest type of soil
- does not hold water
- does not hold nutrients
- it has intermediate size particles
- drains better than clay soil
- lacking in humus
- holds more nutrients than sandy soil
- the particles are tiny and bind together, making it heavy and difficult to work
- cold soil, which promotes slow plant growth
- richer in nutrients than sandy soil
- retains water; poor drainage; the soil is often waterlogged
- deficient in air, plants may not get enough oxygen
- is useful in hot, dry seasons
- this mixture of sand, silt and clay is ideal for a vegetable garden.
I recently did a live stream on Youtube covering all the soil types in detail. You will learn how to alter them to grow and get great results.
The texture of your soil affects drainage and the availability of nutrients. To know the texture of your soil, you should consider the following. Does it feel gritty? That means it has too much sand. Is it powdery? Too much silt. Is it sticky when wet? Too much clay.
However, no matter the texture, all soil can be improved over time by taking some steps, including incorporating organic matter. Sandy soils, for instance, comprise large soil particles, so water and nutrients run through gaps more easily and quickly.
Adding organic matter such as compost to sandy soil helps fill the spaces between sand particles, improving the soil’s ability to retain water and nutrients.
Clay soils, on the other hand, contain tiny, densely packed particles that hold moisture but don’t allow much air space for plant roots. Compost helps separate those tiny clay particles so water can drain more freely and plant roots can get needed oxygen.
Soil fertility is necessary for the soil to sustain plant growth and optimize crop yield. Fertility is a combination of essential nutrients and a soil pH level that makes these nutrients available to plants. There are different kinds of soil fertility:
Inherent / Natural Fertility:
Soil naturally contains some nutrients which make it inherently fertile. Among the plant nutrients, nitrogen, phosphorus & potassium is necessary for the normal growth as well as yield of the crop. Natural fertility is a good thing to have. However, it has a limiting factor in that fertility is not decreased.
This is fertility developed using manures & fertilizers, tillage, irrigation, etc. Acquired fertility also has a limiting factor. The yield does not boost remarkably by the use of too many fertilizers. It is essential to apply fertilizer based on the nutrient content of the soil. Thus the fertilizer should not be too much.
How to improve soil fertility
There are ways to improve soil fertility and several things to consider.
One major class of improvements in organic matter is the partially decomposed remains of soil organisms and plant life, including lichens and mosses, grasses and leaves, trees, and all other kinds of vegetative matter.
Organic matter makes up a small fraction of the soil (normally 5 to 10 percent), but it is essential. It binds together soil particles allowing air and water to move through the soil. Organic matter also retains moisture (humus holds up to 90 percent of its weight in water) and is vital as it absorbs and stores nutrients. Organic matter also serves as food for microorganisms and other forms of soil life.
You can increase the amount of organic matter in your soil by adding compost, aged animal manures, green manures (cover crops), mulches, or peat moss. Some of them are discussed below:
Manure is rich in nitrogen which is good for the soil. All livestock manures can be valuable additions to soil. Manures contribute more to soil aggregation than composts, which have already mostly decomposed. Adding animal manure to your garden provides nutrients, builds organic matter, and adds microbial action.
Animal manures supply different nutrients depending on the animal species, feed, bedding, and manure storage practices. Timing also plays a significant role in just how much nutrients become available to the plants. Thus when the manure is applied and how quickly it is worked into the soil affects soil fertility.
Fresh manure can be too hot for plants and may burn them, so it’s best to use composted or aged manure. If you are using fresh manure, let it sit for some time. (Don’t apply most fresh manures to growing plants). A few examples of animal manure include:
- Chicken Manure: Highest in nitrogen and one of the “hotter” options. It would help if you let it compost and age well before applying.
- Horse Manure: easily accessible but may contain the most weed seeds, although if the compost pile reaches a high enough temperature, this can reduce the weed seeds.
- Goat/Sheep Manure: This is a drier manure. It still smells, but it smells less and doesn’t burn as much as others. The little pellets make it easy to apply, too.
- Cow Manure: A great all-purpose manure that doesn’t burn plants as easily due to lower nitrogen content. Generally, fewer weed seeds than horse manure.
- Rabbit Manure: This is considered “cold” manure, so you can add it directly to plants without worrying about burning them. The pallets will disintegrate slowly and release nutrients into the soil as they break down.
Composting speeds up the natural decomposition process by which organic materials are broken down and their components are returned to the soil. It is a means of recycling almost any organic waste.
It reduces the bulk of organic materials, stabilizes their more volatile and soluble nutrients, and speeds up the formation of soil humus. You can turn your kitchen and yard waste into compost with little effort. Compost adds both nutrients and organic matter to the soil, and it also helps with water retention.
There are two types of composting –cold composting and hot composting. Cold composting is as simple as collecting yard waste or taking out the organic materials in your trash (such as fruit and vegetable peels, coffee grounds and filters, and eggshells) and then combining them in a pile or bin, keeping them over a year so that the material will decompose.
Hot composting is faster—you’ll get compost in one to three months during warm weather. Four ingredients are required for fast-cooking hot compost: nitrogen, carbon, air, and water. Together, these items feed microorganisms, speeding up the decay process.
To learn how the composting process works and how to get the best nutrient-dense compost, watch the video below, where I take you through all the information in an easy-to-follow guide.
Below are materials you can compost
- Vegetable scraps
- Fruit scraps
- Grass and plant clippings
- Shredded newspaper
- Dry leaves
- Coffee grounds
- Finely chopped wood and bark chips
- Sawdust from untreated wood
Do not add onions and garlic to your homemade compost pile. These vegetables are believed to repel earthworms, a vital part of your garden.
Below are materials you should not compost
These materials will do the opposite of what you expect them to and might even damage your plants. Avoid these items for a successful compost pile:
- Anything containing meat, oil, fat, or grease
- Diseased plant materials
- Sawdust or chips from pressure-treated wood
- Dog or cat feces
- Weeds that go to the seed
- Dairy products
3. Cover crops
Also known as green manure, cover crops are grown on unused soil with the intent of tilling them in and letting them decompose. The roots keep the soil loose, and the plants suppress weeds.
Green manures draw nutrients from the soil, storing them in their bodies. These crops are not harvested & taken away from the land as this will take away the nutrients but are tilled into the soil while still green. Later, the plants gradually decompose and slowly release all these nutrients to the next crop.
There’s a cover crop for every season, climate, and gardening strategy. You may consider fast-growing grain grasses such as rye, oats, wheat, and barley, which are a good choice in early spring.
Cold-hardy legumes, such as peas, can be started in late winter and allowed to grow two months or longer to precede a warm-weather, heavy-feeding crop, such as winter squash. Warm-weather legumes, such as soybeans or cowpeas, can fertilize beds that will be planted to fall crops that need rich soil, such as broccoli, garlic, and shallots.
To learn more in detail about cover crops and green manures, you can read a recent article I made about them here
Mulch is a layer of material applied to the surface of the soil used to trap and absorb soil nutrients. Reasons for applying mulch are conservation of soil moisture, improving fertility & health of the soil, decreasing weed growth, and enhancing the area’s visual appeal.
Mulching the soil around vegetables in wet climates will provide a cozy home for slugs likely to decimate your crops. However, certain mulches work well and don’t attract slugs. You can learn more about this in the video below, where I take you through the mulch in the garden.
5. Crop rotation
Crop rotation is planting different crops in one spot, coming after the harvest of one plant. A well-designed process can help improve your garden soil. If you include legume family members, such as peas and beans, they will fix atmospheric nitrogen and deposit it in your soil.
It would be best if you also aimed to alternate heavy feeders with light feeders so you don’t exhaust your soil. Examples of heavy feeders include cabbage, potato, leeks, and perpetual spinach; some light feeders include carrot, beetroot, and onion. The key to successful crop rotation is knowing what plant belongs to what family
Here are some other major family groupings:
- Cucurbits: Squash, cukes, pumpkins, melons, and gourds.
- Alliums: Onions, leeks, and garlic.
- Brassicas: Broccoli, cauliflower, cabbage, kale, Brussels sprouts, turnips, radishes, Chinese cabbage, mustard greens, and collards.
- Umbellifers: Carrots, parsnips, fennel, parsley, and dill.
- Legumes: Beans, peas, and soybeans.
Just know what plants belong to which family and make sure to plant from another family in another growing season.
Improving soil life
It is tough for us to fully appreciate what goes on in the soil. There are many creatures toiling away relentlessly. Healthy soil is teeming with life, with soil organisms doing lots of underground work; they’re certainly not getting paid for.
Soil organisms include bacteria and fungi, protozoa and nematodes, mites, springtails, earthworms, and other tiny creatures found in healthy soil.
These organisms are essential for plant growth. In one gram of soil, the number of bacteria ranges from 100,000 to several billion.
They help convert organic matter and soil minerals into the vitamins, hormones, disease-suppressing compounds, and nutrients plants need to grow.
Their excretions also help to bind soil particles into the small aggregates that make the soil loose and crumbly. Every gardener would want such an amazing activity and should thus create the ideal conditions for these soil organisms to thrive.
This means providing them with an abundant source of food (the carbohydrates in organic matter), oxygen (present in well-aerated soil), and water (an adequate but not excessive amount).
Note that the warmer the soil, the more active these microorganisms are and the more nutrients they release.
Air and Water
Healthy soil is about 25 percent air. Healthy soil will also contain about 25 percent water. Insect microbes, earthworms, and soil life require this much air and water.
The air in the soil is also an important source of atmospheric nitrogen that plants utilize. Well-aerated soil has plenty of pore space between the soil particles or crumbs.
Fine soil particles (clay or silt) have tiny spaces between them – sometimes too small for air to penetrate. Sandy soil has large pore spaces and contains plenty of air.
To ensure a balanced air supply in your soil, add plenty of organic matter, and don’t step in the growing beds or compact the soil with heavy equipment. Note that too much air can cause organic matter to decompose too quickly.
Water, like air, is held in the pore spaces between soil particles. Soil with large pore spaces allows water to move to the root zone and into the subsoil.
Sandy soils have spaces between the soil particles so large that gravity causes water to drain down and out very quickly. That’s why sandy soils dry out so fast.
Small pore spaces like that of clay allow water to migrate back upwards. Water has filled the pore spaces in waterlogged soils, forcing out all the air. This suffocates soil organisms as well as plant roots.
Ideally, your soil should combine large and small pore spaces. Again, organic matter is the key, as it allows the formation of aggregate, crumbs, or soil. Organic matter also absorbs water and retains it until plant roots need it.
Be careful when applying water to the soil. The most common type of stress the soil may face is moisture stress. Overwatering or under-watering are two types of moisture stress.
If the soil receives too little water to prevent transpiration and conserve moisture, it may rely on water in the plant. On the other hand, if your soil is too wet or watered more than necessary, this can have the same effect on your plant as keeping the soil too dry, i.e., dehydration.
If you keep this up with the soil for long periods, the plant may go through root rot, which will not allow it to take up water, dehydrating your plants and making them turn yellow. It is important to check how much moisture your soil is getting regularly. To do this, press a finger into the plant’s soil (about an inch).
Make sure to go beyond the soil’s surface, as it tends to dry out the fastest. If the soil is dried an inch below the surface, you likely need to water it immediately. If the soil feels damp an inch below the surface, your soil may be getting enough water.
Because most soil life and plant roots are in the top 6 inches of soil, concentrate on this upper layer.
Your plants require many factors to work properly to ensure they are healthy. One major factor is your soil. Getting soil to plant on is not usually a problem.
What is more essential is getting your soil fertile to increase productivity. Every gardener wants their plants to yield the best harvest, but they often neglect the value of good soil.
The soil fertility can be improved with some of the methods highlighted in this post. You can be sure your plants will do better than you expect.
Remember to try to find a balance. Do not feed your soil too much organic matter or water; try to ensure the pores are not too porous or too compact so that adequate air can enter. All in all, you can use this guide to improve soil fertility and increase productivity.
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Remember, folks, you reap what you sow!