Understanding soil and three basic tests to get you started.

    It might seem like everyone should know what soil is. We walk on it, we dig it up, we, build structures on it, and of course, plants and animals live in and on it. It might surprise you just how few people actually understand it. To quote my geology teacher: "Dirt is what wash out of your clothes. However, when it's on the ground it isn't just dirt! It has a composition, a structure, and an ecosystem going on in there. So from now on, use the term soil!". 

    Many might not think about it much, but soil differs from one location to another. It can also change over time. But what types of soil are there? You might have heard words at some point like "clay" soils, "sandy" soils, "silty" soils, perhaps even a mysterious "loam".

    Soil is made up weathered rocks with varying mixes of:

    • Sand -  The largest of particles, great for aeration and drainage, poor for nutrient and water retention.
    • Silt - The middle-sized particle, closer to clay than sand in size. Not quite as hard to work with as clay, and doesn't form clumps as readily. But holds shape better than sand. This has a higher nutrient and water retention than sand, but without the worst problems of clay. However, it's one of the first to be eroded away since it doesn't have the heavy particle weight of sand, nor does it clump as well as clay.
    • Clay - Clay has the smallest of the particle sizes. It is nutrient rich, and can retain water too well at times. Because it's particles are so small, they pack together very tightly and form a very heavy and dense soil. Clay becomes particularly difficult to work with when it's wet yet can form a water-impermeable barrier if left on top, which increases run-off and erosion.

    When you have all three mixed in roughly equal measure, you get that "loam" style of soil which I mentioned above. However, you can have a somewhat even mix with a little more sand, silt or clay. In which case they're called a "sandy loam", "silty loam", and "clay loam" accordingly. Try the next test with your own soil, to find out what you're dealing with.

    The soil test anyone can do at home. The jar test:

    Now many people call this the "Mason Jar Test" but the fact remains that any glass jar with a well-sealed lid will work. I recommend one with vertical sides and as flat a bottom as possible to make sure your results are accurate. Watch this video on how to do that.

     

     

    Soils also contain things like small rocks, organic matter, and it's own locally-specific ecosystem of worms, ants, beetles, fungi, bacteria, nematodes, and many many more. In short, the more life that lives in your soil, the healthier your soil will be. Biodiversity isn't just a popular "buzz word", it refers to a bunch of different living things, each playing their role to balance any problems that might arise. So if you start having a problem with aphids eating your plants, then a natural predator such as Ladybugs will increase appropriately due to the increase in food. Of course, there's a bit of a lag between imbalance/rebalance, but nature has been doing this for a lot longer than we humans have been around.

    Cue the "Soil my Underwear" campaign and soil biodiversity test:

    Soil Your Underpants Challenge
    The "Soil Your Underpants Challenge". A fun way to raise awareness about soil ecology and biodiversity.

    Now, don't believe each respective article on how "Oregon, or California, or Canada" came up with this somewhat amusing soil test. The test has actually been around for a while, but using less "attention grabbing" garments. It effectively involves planting a new pair of 100% cotton underpants up to the waistband in your soil and leaving it for two months. Dig it up, and the less that remains of your underpants, the better your soil biodiversity is. For more information, see this video:

     

    We've talked about soil composition, and a fun way to measure biodiversity, let's get a little more technical and start talking about pH.

    Measuring Soil pH:

    Soils can range from quite acidic to quite basic (some call it alkaline). Most plants do best in "neutral" soils, although there are plants such as citrus, blueberries, and tomatoes which like a little bit of acidity. Meanwhile, the humble guava prefers soils to be a little basic/alkaline. To make sure your soil suits your plants, you're going to have to test it.

    The pH scale ranges from 0-14 where 0 is extremely acidic, and 14 is extremely basic/alkaline. Neutral falls somewhere around the 7 mark, but how far on either side is "still neutral" seems to be debated. Most agree that ranges from 6.5-7.5 are considered neutral.

    The pH scale shown by the colour of universal indicator
    The pH scale shown by the colour of universal indicator (used in soil pH test kits)

    Soil pH is important because it significantly impacts how easily plants can absorb certain soil-based nutrients. It's also a measure of how hospitable the soil is generally to various forms of life, ranging from microbes to worms and bugs. A more in-depth explanation can be found here:

    http://www.oakleafgardening.com/how-to/understand-your-soil/soil-ph/

    So in short, if your pH is not suited to your plants, you'll find that the plants become nutrient deficient, and may not grow very well, or perhaps in extreme cases, die.

    One thing about the pH scale is that for each number away from neutral (7) you go, the acidity or alkalinity (depending on the direction) goes up ten times the previous number. For instance, a pH of 5 is ten times more acidic than 6. A pH of 4, is 100 times more acidic than 6. Similarly, a pH of 12 is ten thousand times more alkaline than a pH reading of 8. So you really want to keep things at least vaguely neutral.

    In general, soils become more acidic over time as plants absorb some nutrients, as well as rain (being slightly acidic) will push things toward a more acidic reading. This isn't always a bad thing, as some plants will love this. However, if you're getting down to pH readings of 5 or lower, or above 8.. you're probably going to want to adjust the soil a bit.

    Now there are two ways to test pH. The chemical test, and the electronic pH tester. I like the idea of the electronic pH tester, (fewer chemicals used, and generally less fiddly) but they're often inaccurate. Good electronic pH soil probes need to be kept in neutral solutions, and recalibrated with specific (and expensive) solutions that are made to be specific values. The chemical test is much like the ones people use to test their pool water, and can be bought in most hardware stores.

    Soil pH Test Kit
    Soil pH Test Kit, available from most hardware stores. This one just happened to be available from my local Bunnings.

    Solving soil problems:

    Some of the existing "solutions" that people use to deal with soil problems are in fact, the source of many problems. Ploughing, digging, and exposing soil actually weakens soil structure, and causes all sorts of upheaval to the soil ecosystem. It also increases erosion, and degrades the soil itself through nutrient loss. Adding chemicals further creates imbalances, and changes the soil composition which the soil ecology might not handle well. I'll discuss this in broader, more environmental approach below. However, these same principles and concepts apply equally to gardening.

    It might sound weird but you can of course, treat each individual problem with a specific treatment. For instance, if your have soil that's too basic/alkaline, you can add some acidifying substance like sulphur (Americans spell it "sulfur", just to be different). Similarly, adding lime or even wood ash can help with acidic soils. However, getting the mixes right can be very difficult, and the results might take longer to achieve than expected, and not always last as long as you might think. I don't want you to think that you need to buy a multitude of chemical additives to maintain soil health. This is what most people assume, and it gets expensive, and  can be counterproductive.

    If your soil is too rich in clay, you might think that adding sand would help with the drainage, but DON'T because this leads you to make a mix that is less like soil, and more like concrete... especially if it dries out. There are some gypsum based additives you can buy to help break up the soil but there's a better way. Try growing root vegetables like beetroot, carrots, radishes, and potatoes in clay (your crops won't be great in the initial season because the clay may slow growth), but you'll find that the plants break your clay up for you.

    If your soil is too sandy, again, don't try adding clay (again the concrete thing)... instead take my advice and apply the "universal soil improving method"....

    If you learn absolutely nothing else from this article:

    Soils are best adjusted by simply adding organic matter, compost, and mulch. Seriously, that's it!

    Keep adding this over time, and the soils will improve! No problems with concrete hard soils, no expensive and often imbalanced nutrients. No fertilizers running off and causing blue-green algae problems. Organic matter helps to solve soil pH imbalances, nutrient deficiencies, and encourages soil-based life forms to come and inhabit a nice bit of soil. Leading to more aeration, the increased availability of nutrients, and healthier plants. Healthier plants are more resistant to pests, which reduces the need for pesticides, which saves you more money, while increasing yield quality and quantity.

    Why has soil degradation become such a problem?

    That's a long, complex story that really became an issue with colonization of numerous lands across the planet, exacerbated by the industrial revolution, the rise of the commercial mono-culture (single crop) style of agriculture, and the continued lack of understanding about what humankind has been doing to the environment.

    Problems with human intervention with soil up to this point:

    I was raised on a farm, and although my family has since opted for the "urban" lifestyle, I have seen the notable and steady decline of soil quality in many places in the course of just my life time. (I'm still under 40). In my high-school days, I worked with what was then called "The Department of Land and Water Conservation", which was monitoring the growing problem of salinity and land degradation. Poor farming practices have not only become mainstream, they've now become something akin to tradition. Trying to convince farmers to change when they're still following the practices of their grandparents, or even great grandparents is challenging at best.

    What's wrong with historical practices?

    The industrial methods of farming that have become the mainstream method of farming today place "ease of work" and "short-term economic forces" ahead of sustainability. Unfortunately, when farmers detect "a pest" they effectively carpet-bomb entire fields with pesticides that kill far more than the intended pest. That's after we've ripped out the native plants, ripped up the soil structure with ploughs, planted commercial crops for miles, over-watered soils that aren't conditioned for it, then we harvest "the good bits" and then rip out/burn/plough in the remaining (albeit reduced) plant matter. Farmers do that over and over again as each crop finishes, allowing bare soil to blow away in the wind, or be washed downhill. Which requires more chemical fertilizers (which can really mess up the soil ecosystem) to make up for the substantial nutrient losses that accumulate over time. Monoculture-based farming causes a lot of problems, and if you have a farmer that's "purely in it for the money", with dreams of selling up and living their retirement on the beach somewhere... it can be extremely hard to convince them to change.

    Newer, better practices are starting to be seen in pockets around the world, but are still utterly dwarfed by the older farming methods.

    Interestingly, tiny farms which grow a variety of crops simultaneously, far exceed the productivity per hectare/acre of the larger mono-cultural farms. They have less pest problems, and slowly restore their soil in ways formerly unheard of. However, can it be profitable? Obviously this varies based on knowledge, expertise, climate, and of course, effort.  Having said that...

    The rise of the "Market Gardener", "Agro-forestry", "Permaculture", and "Biodynamics" have enabled people (not just "Hippies" to grow organic vegetables by contract with local restaurants on very small plots of land of just a few acres and generated income to support their families and send their children to "College" in the U.S. (That's no small feat!) I'm not saying that it's a lifestyle for everyone, but even if you choose to learn a little and apply it to your own backyards (literally and figuratively) then you might be surprised what you can accomplish.

    Cue our slowly-growing (and very late) awareness of soil ecology.

    We as humans have been more than a touch self-centred as a society for a long time, and as such we have little understanding of the environment in general. While cute Pandas, Elephants, and Koalas get lots of attention (and thus funding and research looking at preserving them), the creepy-crawlies (insects, arachnids, etc) get comparatively negligible  funding and very little research. Almost perversely, we struggle to focus on what is likely to be more important since we (and the cute animals) are far more reliant on insects survival (however indirectly) I can assure you.

    However, the fact remains that people across the world whose entire livelihoods depend on soil, are actually destroying it through poor farming practices, deforestation, urban sprawl, and huge earth-moving activities such as building dams, "reclaiming land", and mining.

    We build cities on some of the best land Australia has to offer. While we grow ridiculous water-hungry crops like rice and cotton in what is effectively, desert. So there's a lot of room for improvement from what we're doing at the start of the 21st century.

    To sum up:

    I hope I've helped you to understand soils just a little bit better, and how to test your soils. I've also outlined some of the problems of soil degradation caused by (primarily agriculture) but also numerous other human activities. I'm not here to blame anyone in particular, but to outline some of misguided beliefs in the hope that inspires real change, at whatever scale. If you have even the tiniest plot, or have nothing but pots, and start appreciating your soil just a little bit more, then my time spent gathering these thoughts and materials won't be wasted.

    I wish you happy gardening and hopefully healthy "soiled" underpants! :-P

     


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