Ever heard of soil leaching? In case you were wondering, leaching doesn't refer to the blood-sucking leech. So don't worry, this process won't require you to handle anything slimy.
Instead, leaching is a natural occurrence that gardeners should be aware of and, if needed, can purposefully implement to improve soil's habitability for garden plants. Maintaining your garden's soil health isn't difficult – it just takes vigilance.
Using nutrient rich gardening soil, watching moisture levels, providing decent drainage through a raised garden bed, and occasionally leaching will ensure your plants have a place to thrive.
What is leaching?
Leaching occurs when minerals, fertilizer, pesticides, and salt drains through your garden soil into the subsoil and rock below. The process is initiated by water flow, like rain, which saturates the soil and pulls soluble compounds downward. Leaching doesn't know the difference between bad chemicals and beneficial nutrients, however, so it can leave your soil barren and unable to support plant life without periodic enrichment (think fertilizer or compost).
Gardening is a cyclical process of adding and removing components within your garden so plants always have fresh water and minerals to grow. If no leaching occurs, buildup in the soil will choke plants out just as quickly as over-leaching.
Bryan Traficante, co-founder at GardenInMinutes.com notes: "Leaching garden soil is something I mention often to people starting a new garden. When starting out, many gardeners often over-fertilize at the onset out of excitement or don't water plants thoroughly enough. I've done it myself! Both habits usually lead to excess salt buildup in soil though, which will eventually kill your plants if the soil isn't leached."
Soil comprised mostly of sand will drain quickly, but too quick and the plants won't have time to absorb water. Clay, on the other hand, retains water and minerals very well. However, too much clay prevents leaching and prohibits plants growth. That's why most readily available gardening soil is a mixture of both (among other additions).
Additionally, the type of garden you use can greatly aid with your soil maintaining its health and plant growth. Raised garden beds provide you with better control over your soil's density – as in how packed it becomes - and easier drainage. Soil settles over time and rain packs it together which inhibits both drainage and root growth. In a raised garden bed, soil is added at your discretion (allowing you to keep it more loose) and with no bottom to a raised garden bed, water drainage can happen more freely and deep rooting plants can grow without barrier.
Benefits of leaching
As mentioned earlier, leaching clears the soil of excess compounds and most commonly - salt buildup. For example, if you put too much fertilizer into your garden, you will likely notice plants start to get brownish ends and begin to look sickly. Instead of replacing the soil in your garden bed, you can water it for a longer than normal duration of time to flush out (leach) the excess from the soil. Basically, what you'll do is water your garden (without flooding it) for an extended duration of time to a point at a significant volume of water has passed through the soil (you will see water eventually coming out of the bottom of your garden bed, which is good!)
Consequences of leaching
Unfortunately, there is always the potential of too much of a good thing. Leaching isn't an exact science for each garden (unless you get your soil tested consistently... but for this article we'll assume you don't). When you leach your garden soil you may remove too many compounds and nutrients - as we noted before, leaching doesn't discriminate 'good' from 'bad' compounds in your soil. A simple rule to apply is, if your plants begin to develop brown tips or you fear you've over fertilized, give your soil a good leaching. If plants then begin to wilt in the coming weeks, you may need to add some nutrients back in with fertilizers/compost etc. The key though is moderation, test and repeat!