Posts tagged tillage

Minimize tillage, part 3

February 5, 2010 · Filed under Gardens, Landscaping · Tagged , , , ,

Tillage and soil disturbance brings one other thing to light – weed seeds. I can’t help but think about weeds at this time of the year since I’ve casually observed plenty of patches of weedy hell just traveling through residential neighborhoods.

Weeds will get away from you if you don’t stay on top of them. That’s just what weeds are consummately equipped to do thanks to their genetic heritage and reproductive strategy – live fast, die young, and crank out seeds in vast numbers. The seeds then bide their time near the soil surface until the conditions are right to replicate the growth cycle all over again.

The plant species we call “weeds” are really nothing more than plants we have judged as unwanted because they’re the wrong plants in the wrong places. For one thing, they tend to be non-native to the places that are being colonized. For another, weedy species tend to not encounter built-in biological controls that keeps their population growth in check in their native ecosystems. That means that nothing in their new host environments has learned to exploit the weeds as a food resource…yet.

For lack of natural controls to keep weed populations in check, it’s on us to impose that constraint in our gardens and landscapes. It’s late April now in Southern CA and the majority of weeds have set seed. The best time to set the weeds back is just after the first winter rains. Let the weeds grow up a bit but and then pull (deep tap rooted species like dandelion, wild radish, or cheeseweed) while the soil is still moist or mow them (grasses only) when they’ve set flower (inconspicuous on grass species) but don’t wait until the weeds set seed. Like many things in life, timing is everything. If you’re wondering why it’s not helpful to wait until the plants set seed, it’s because the seeds of some species are viable plant embryos long before they’re separated from the parent plant. When you wait, you inadvertently add to the weed seed “bank” in the soil.

Tillage makes things worse. Some weed seeds no doubt are killed in the process but the majority are just “warehoused” by tillage. It’s like putting them in the equivalent of a bank security deposit box. Without tillage, most seeds will remain at the soil surface. Ants carry some seeds away, earthworms consume other seeds and redeposit them in castings, and gophers and other animals move seeds through burrowing. Broad scale tillage helps foster an “out of sight, out of mind” mentality. Sure, the weeds for that season or that year may be gone but the seeds of their ancestors lie in wait to return with a vengeance.

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Minimize tillage, part 2

February 2, 2010 · Filed under Gardens, Landscaping · Tagged , , , , , , , , ,

Did you know that the top foot of soil has more 7 to 50 times more life than the next 3 1/2 feet? (Source: Designing and Maintaining Your Edible Landscape Naturally by Robert Kourik, Metamorphic Press 1986). When soil is tilled or plowed, too much air is introduced all at once.

Life thrives in a zone of ‘enoughness’. Now I realize this is a foreign concept to most people, who as a rule want more, more, more of everything and then some. (This proclivity has led to such pop culture aphorisms like, “Too much of a good thing is just about right.”) Think about it though: more consumerism leads to more waste and more waste leads to more plastic waste as a proportion of that overall waste stream. More plastic waste leads to larger oceanic garbage patch gyres, of which there are currently five. But, I digress. More oxygen in the soil introduced like a shot of steroids does not lead to more life but to less. You may think you’re taking care of one problem – say for instance a pest outbreak – but you’re unintentionally creating a lot of new problems for yourself. You’re also destroying the soil’s structure, especially if you are tilling over and over from year to year. (There are techniques to aerate the soil less violently, but those may be introduced in later posts.)

Imagine taking a whole block of any given urban development – New York, Paris, London, Scottdale, Tokyo, Los Angeles – and upending that entire block, buildings, streets, and all. What used to be the tops of buildings are now underground and beneath everything else that used to be above them. Don’t you think that would be quite disruptive, to say the least?

Turning the soil is no less deadly. Soil flora and fauna tend to live in specific strata in the soil and tillage disrupts this order. For instance, there are some native California earthworms (yes, they exist! – check out this paper) that tend to tunnel deeply and other species that live closer to the surface. If you’re smart and letting nature do the heavy lifting for you, the only creatures that are turning the soil the vast majority of the time are earthworms and other ground dwelling animals that tend to tunnel. You may not like the affect these creatures have on the visual appearance of your landscape or your plants, but the truth of the matter is that tunneling mammals have their roles to play in nature. They introduce all-important organic matter, for one thing.

For those of you who grow edibles, especially produce that commonly graces our tables, you have a sense of humus. This is organic matter that has been consumed and altered by soil fungi and bacteria into large amorphous molecules that tend to resist further decomposition. Humus does break down but it does so very slowly. The introduction of too much oxygen through tillage burns up organic matter quickly and most of the nutrient value is lost. If you’re a gardener, why would you want to engage in a practice that is counterproductive and against your own interests?

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Minimize tillage, part 1

January 26, 2010 · Filed under Gardens, Landscaping · Tagged , , , , ,

Are you one of those property owners who tills? Why do you till? More importantly, what do you believe that tillage achieves?

Maybe you think that the soil needs more oxygen. I’ll grant that soil life, including the plants, needs a combination of moisture and oxygen to survive, but soil with good texture already has oxygen in it! Soil that isn’t compacted from constant foot or vehicular traffic is just fine as it is.

Imagine a clear plastic or glass container filled with ball bearings. If you shake that container, the ball bearings will settle into an arrangement that minimizes the spaces between the bearings. This is what soil compaction would look like if you could magnify soil particles. But soil isn’t composed of only one particle size! The magical stuff that is soil is composed of varying particle sizes. If you go back to the image of the container with the ball bearings, now picture those ball bearings mixed in with kumquats, ping pong balls, tennis balls, and the occasional basketball. Those varying particle sizes allow for air and water to infiltrate the soil.

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