Unless you're using a syringe, you've never really fed or watered your plants. When you irrigate or fertilize your plants, what you are really doing is watering and feeding the soil. It is the soil that feeds and waters your garden and plants.
Creating healthy Morgan Hill soil is the best way to grow healthy plants that need less protection from pests and diseases, produce more flowers and food, and require less work. Let's learn more about growing great soil.
What is great soil?
What is in your soil?
The only way to really know what is in your soil is with a test from a reputable lab. The Olson test is better for the West Coast, while the Brays test is better on East Coast. In the Bay Area, we tend to have clay soil that is highly prone to compaction. Aeration is frequently needed. Clay soil tends to contain plenty of most of the necessary minerals, and too much salt and phosphorous. Iron and nitrogen deficiencies are common in the Bay Area. Your soil test results should include percentage ratings for each of the major plant nutrients. It may also tell you how much organic matter is in your soil.
Organic matter in soil
Organic matter is critical to soil health, and it can range from 1 to 8 percent. As living things die and begin to breakdown, they add nutrients and improve soil structure. They also alter the electrical charge of soil. Ensuring there is enough organic matter in the soil also improves porosity, aeration, and biological activity.
Soil is usually described as being sand, loam (silt) or clay. Sand is big. You can see individual particles. And water and nutrients can drain away quickly. Loam is made up of medium-sized particles that hold a good balance of gases, liquids, minerals and organic matter. Clay is made up of extremely tiny particles that can hold a lot of water and minerals. Organic particles surrounded by clay are protected from the microorganisms that break them down into nutrients that can be used by plants, creating an unattainable banquet. Each type of soil benefits from the following:
Sand — add organic matter to help it retain water and nutrients
Loam — add organic matter to help maintain the inorganic mineral and organic matter balance
Clay — add organic matter to improve soil structure and porosity, and to speed the breakdown of organic matter
Adding organic matter to soil is critical to plant health. A one percent increase in organic matter can make a profound difference in soil structure. This helps plant roots get to and absorb nutrients. You can add organic matter to your soil by:
• Mulching with untreated chipped wood
• Amending with composted kitchen and yard scraps
• Incorporating aged manure from local horse and cattle farms
• Raising chickens and composting their soiled bedding
• Protecting bare soil with ground cover crops
• Applying organic top dressings
Once you've increased the amount of organic matter, you will want to add nitrogen. Nitrogen levels are the single most limiting factor in most gardens, and organic matter can help plants access the nitrogen already present. Most soils contain less than 1 percent nitrogen, while 2 to 5 percent is ideal. Which form will you use? Inorganic nitrogen can be found as nitrites or ammonium. When roots take up nitrates, they increase the pH of the immediate area, making it more alkaline. The opposite is true when plants take up ammonium, making the soil more acidic. Organic sources of nitrogen include blood meal and cottonseed meal, both of which will acidify soil.
You can't know which form of nitrogen is right for your soil until you know its pH. Soil with a low pH makes it harder for plants to access some macronutrients. Soil with a high pH does the same thing. Most plants prefer a pH of 6.0 to 6.5 to thrive. Growing great soil means identifying and managing your soil's pH.
Creating healthy soil
Soil creation is called pedogenesis. You can create great soil in your garden and landscape when you:
1. Learn what you already have, with a reliable soil test.
2. Regularly incorporate organic matter with compost, mulch, and even coffee grounds.
3. Analyze your soil structure and aerate, as needed.
4. Only add needed amendments, and in the proper form for your soil.
5. Determine your soil's pH.
Other ways to improve your soil's health is by growing cover crops, using crop rotation, installing foot paths to reduce compaction, and avoiding irrigation run-off and urban drool.
For more information, visit UC Master Gardeners or call (408) 282-3105 between 9:30 a.m. and 12:30 p.m., Monday through Friday.
by UC Master Gardener Kate Russell
Image: Soil Textural Classes: California Master Gardener Handbook
This article first appeared in the June 21 — July 4, 2017 issue of Morgan Hill Life.
Do you have an area in your yard where you just can't get anything to grow? Have you struggled repeatedly with a prized plant or tree that just won't thrive? If you know what type of soil you have and are watering properly, it may be time to dig a little deeper to find out what's going on.
Check your soil texture. It dictates the way your soil drains and the amount of nutrients available to your plants. Providing the appropriate amount of water across the entire bed and at the right time also is of utmost importance.
Soil compaction is the next thing to look for. When soil is compacted, the air pockets are compressed, making it harder for roots to expand and grow and therefore harder for the plant to take up water and nutrients. Soil becomes compacted by foot traffic, use of heavy machinery, working the soil in overly wet conditions or when proper amendments — organic matter — haven't been added.
To improve your soil, apply a 2- to 4-inch layer of compost once or twice a year.
Aerating, especially in lawn areas, also can be helpful.
Soil pH is another important factor; it determines how acidic or alkaline the soil is, which affects plant growth, soil bacteria, availability of essential nutrients and soil structure as well.
Acidic soil has a low pH, and extremely low levels can cause a plant to become stunted or die. Plants that thrive in acidic soil include blueberries, azaleas, rhododendrons, hydrangeas, gardenias, camellias, crepe myrtles and pine trees. Adding soil sulfur, peat moss or iron sulfate will decrease the pH level.
Alkaline soil is high in pH and is generally deficient in nitrogen and other important minerals. A high-alkaline soil has higher levels of sodium that may be toxic to plants. Plants that grow in alkaline soil include clematis, heuchera, delphinium and dianthus.
If your plants have pale green or yellowing leaves, that may be a sign of nitrogen deficiency. Plants may be stunted or have much smaller leaves than normal. To increase nitrogen, add good-quality compost; grow cover crops, such as fava beans, borage and vetch, in the offseason; or add coffee grounds to the soil.
The amount of soil organic matter — decomposed plant and animal residues -- really does matter. It has been called the most complex and least understood component of soils. High levels of soil organic matter improve water and nutrient retention; help fend off compaction and erosion; balance pH levels; and even bind harmful pesticides and trace elements, keeping them from polluting our watersheds.
To increase soil organic matter, apply compost and mulch, reduce tillage, leave grass clippings on the lawn and rotate crops in your garden.
Earthworms are an excellent and essential indicator of healthy soil. They create burrows in the soil, allowing water to move through the soil and roots to more easily expand and grow. Dig out about 6 inches of soil and count the number of worms you find. Three to five is a good indication of a healthy soil. If you don't see any, your soil is lacking in organic matter.
By UC Master Gardener Rebecca Jepsen
This article first appeared in the July 20 issue of the San Jose Mercury News.
Knowing soil types and water requirements may help us grow healthy vegetable gardens and flowers, but it is also vital when it comes to trees.
Igor Lacan, environmental horticulture adviser for UC Cooperative Extension, says as we move toward warmer temperatures with less predictable annual rainfall, we will need to make smart choices about our landscapes.
“Even in a drought, it is essential to prioritize your trees,” Lacan says. “Trees not only support our native birds, bees and wildlife, they provide major ecosystem services to us as well. Urban trees lower the ambient temperature, thereby reducing the need for air conditioning, sequester carbon from the atmosphere, provide stormwater capture, decrease pollution and enhance the property value and aesthetics of your home.”
Start with soil
In order to practice responsible irrigation — using enough water to keep a plant alive and no more — knowing your soil type really does matter.
Soil type, or texture, refers to the proportions of sand, silt and clay particles in its makeup. Sandy soils are coarse and drain quickly. Plants in sandy soil need frequent watering and may need fertilizer.
Clay particles are very fine and become glued together when wet, and although clay soil can be slow to drain, it retains moisture and minerals, requiring little to no fertilizers.
The roots of newly planted plants may have a harder time getting started if the soil is hard and dense, but once established, plants tend to thrive in clay soils.
Silty soil is found along our riverbeds, lakes and other riparian areas. Particles are smaller than sand but not as fine as clay. It drains well and has good nutrient retention.
Loam represents a combination of sand, silt and clay and most of the Bay Area has clay or loam soil.
To tell what kind of soil you have, moisten a handful of it and give it a firm squeeze. If it holds its shape but crumbles when you give it a poke, you have loam. If it holds its shape without crumbling, you have clay. If it falls apart as soon as you open your hand, you have sandy soil.
Knowing your soil type will guide you in how much water to apply and how often.
To gage soil moisture levels, you will need to dig down to the root level. For trees, use a shovel or an auger to get 12-18 inches below the surface. After watering to this depth, soil should be moist but not drenched.
For mature trees, deep water infrequently, about once a month. Imagine refilling a 12- to 18-inch deep water reservoir around the tree's roots.
It's important to water beneath the entire canopy. Installing a Tree Ring Irrigation Contraption (TRIC) is a great way to accomplish this.
Newly planted trees may need only 10-15 gallons per week, but they may need additional water in extremely hot weather.
In all cases, a good rule of thumb is to water deeply and observe your tree. If the tips of the leaves and branches start to droop, it's time to water again.
You will then be able to properly set up your automated irrigations systems. But remember, they need to be changed seasonally as the weather and temperature fluctuate. Online watering calculators can also be helpful.