We’re at the home garden of soil scientist Emily Leyden. Subscribe 🔔 ab.co/GA-subscribe
Emily got interested in soil science partly because she’s a keen gardener. Her work in academia usually finds her working with farmers and agricultural companies on how they can improve their practices, and environmental agencies work on erosion and salinity. But her real passion is the extension work as president of the SA chapter of Soil Science Australia, helping home gardeners to understand the scientific underpinnings of what makes a good soil, and therefore a good garden.
To achieve the same garden greatness, Emily says there’s a few basic tests any home gardener can do to help better understand their own soil that require no extra equipment. You can do them today! “One you know what you’re working with, it’s a starting point. It’ll go a long to way to stopping you wasting money at the nursery”.
TESTS:
- Testing soil texture:
The first step is identifying what type of soil you have, with a simple soil texture test.
Soil “texture” refers to the proportion of sand, silt and clay in your soil. Texture can influence things like the ability of your soil to hold water, movement of air through the soil and how easy it is for your plants to grow roots.
It’s easy to test by taking a small handful of moist soil, kneading it into a ball and pressing it into a ribbon. The “feel” of the soil ball and the length of the ribbon indicate the texture.
1. Collect a sample of soil sufficient to fit comfortably into the palm of your hand. Check the soil for any lumps, stones or organic material. Break/ remove any that are present.
2. Add water to the soil sample, a little at a time. While adding water, knead the soil to make a small ball that sticks together and is moist.
3. Knead/work the ball for a minute or two.
4. Press the soil between your thumb and forefinger to make a ribbon.
5. Measure only the length of the part of the ribbon that is not broken.
If your soil feels sticky and you can get a ribbon to form that’s at least 4cm long, you’ve got a soil that’s mostly clay. If your ribbon won’t form or falls apart easy, and you can feel individual granules, you’ve got a sandy soil.
If your soil is mostly clay, Emily says “it might need breaking up with addition of sand and compost to increase water flow”. She points out that although water saturation (and not enough air) can be a problem, clay soils do hold onto nutrients better.
If your soil is sandy, Emily says “sandy soils might need clay and compost so water and nutrients can hang around in the soil for longer”.
- Checking for dispersion and salinity:
A soil is called “dispersive” if it has too much sodium (salt) in it. Sodium causes the clay particles in soil to break apart (or “disperse”) when wet, and this can cause problems for the structure of the soil. Excess sodium in soils causes waterlogging, surface crusting, difficulties with water infiltration, poor seedling emergence and poor aeration.
To test if your soil is dispersive:
1. Half fill a clear plastic dish (or jar lid) with distilled water.
2. Place three balls of soil (3-5 mm diameter) carefully into the dish.
3. After 10 minutes, examine how much your soil has dispersed into the surrounding water
If there is no dispersion, the water remains clear. If there is complete dispersion the water will be as opaque as milk. Partially dispersive soils will sit somewhere in between.
Emily says if your soil is dispersive, adding gypsum can help. “The calcium in gypsum replaces the sodium on the soil particles, allowing sodium to leach out…and improving soil structure”.
WHAT TO DO:
Emily says as always, the panacea is compost. “Adding organic matter is always a good idea… it provides energy for soil microorganisms, helps store nutrients and supply and improves soil structure. Better soil structure allows good water and air movement, root penetration, less erosion, holds nutrients better and less water ponding.”
Overall, Emily says the results from these 2 simple tests should inform what plants you’re trying to grow, and pragmatically inform how you’re gardening.
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15 июл 2024
