My neighbors would come by my farmlet and commend me, “Your plants look healthy and pretty. You must have green thumbs.” And I would reply, “It’s not the thumbs, it’s the soil, sun and water.” So now we have an idea of what we want our urban farm to look, smell, feel, taste, and sound like. It is time to examine the small patch of unpaved earth we have.
The first consideration when planting is to choose the correct planting medium which is usually soil or earth. Let us not even think about hydroponics or aquaponics. You take care of your soil; your soil takes care of your plants and all the beneficial organism living around your urban farm. Since we are preparing for a small home garden, we don’t really need to go to a professional soil laboratory and have our soil tested. We can do some practical soil analysis using our senses.
Likewise, we only need a top soil bed of about 6-10 inches. Unless we are transplanting a big tree planting material, we don’t need to dig deep into our soil. Roots generally grow horizontally, not vertically because they get their nutrients from the top soil. If they are in an enclosed container, the roots form into a ball. That is why it is easy to uproot plants. The roots of some plants, though, like vetiver grass and big trees have roots that could grow deeper vertically that is the reason they are used to prevent erosion and landslide. Unless your home garden is sloping 45 degrees, we will not dig into this topic further.
A rich top soil, according to several websites, should have nitrogen, phosphorous and potassium in big amounts. It should also have some measure of calcium, magnesium and sulfur and trace amounts of boron, chlorine, copper, iron, manganese, molybdenum and zinc. Without top soil, it is not possible for plants to live. Plants also need carbon, hydrogen and oxygen from the air, water and soil.
Do you think your soil has all these nutrients your plants would need and an enabling soil structure and texture? Here are a few simple soil test we could use. Don’t be squeamish about these tests because you do it only at the very start of your urban farming initiative and when your plants are starting to look forlorn or are dying.
The squeeze test. Top soil should be porous which allows drainage of water, free movement of air and unobstructed development of plant roots. First, wet the soil but do not soak. To test if our soil is porous, dig a hole 6-10 inches deep and take a fistful of soil. Squeeze this clump of soil in your bare hand. Sandy soil feels grainy, loosely packed with different sized materials and will hold their shape under slight pressure. Silty soil feels like wet powder while clay soil is sticky. Both silty and clay soil form clumps that are hard to break that do not allow for easy flow of water and air.
The earthworm test. Dig up soil from an area 1 foot square and 1 foot deep. Count all the earthworms in the soil you removed. If you have about five or more earthworms, your soil is healthy. Worms could only live in well-aerated soil. If less, you need to add organic matters for the earthworms to feed on and some porous materials to allow for aeration allowing worms to slither with ease around your garden. Earthworms help aerate the soil and increase water flow. Their casts enrich the soil with enzymes, bacteria, plant nutrients and organic matter. They also secrete compounds that help bind soil particles together.
Soil organism test. Good soil teems with organism such as centipedes, spiders, beetles, among others. Dig a hole at least 6 inches and look into the hole. Take not of the number of each specie you find in a 2-4 minute period. You must count a total of 10 organisms. Spiders are easy to spot since you are most likely to trip in their web. Healthy soil have a thriving and diverse population of fungi, bacteria, insects and invertebrates. They help break down organic matters and make nutrients easily absorbed by the plant. They’re also your natural fighter against pests and disease.
Organic residue test. Do you notice leaves, papers, manure and other organic matters littering your yard? Over time this organic litter breaks down, with the help of soil organisms, and becomes organic matter, the single most important component to healthy soil. Dig down 6 inches, and then examine the soil you pull out. Check for organic residue in various stages of decomposition. Smell the soil (ewww). Does it have a sweet earthy smell or no distinct smell, or does it have a greasy, sour, unclean smell? A sweet earthy smell is what you need.
Water availability test. Available water is water in the soil that the plants are able to use. This water does not easily evaporate. To test for water availability, observe how long it takes until plants begin showing signs of needing water again after a soaking rain. Longer times indicate better water availability and indicates good soil structure and presence of organic matter in the soil.
Weeds and grass test. Look at your available soil. Presence of healthy, robust and matured weeds, grass and other plants indicates a healthy soil. You might already have a veritable treasure of pancit-pancitan, mani-mani, tawa-tawa and others. Birds and wind brought them there.
Should your soil fail the tests, don’t despair. You could do some damage control by adding more organic matters to the soil. Or you could also use raised beds and create new top soil. And for those without soil, we will use available containers to hold our soil. That’s for next articles.