What is soil compaction?

In previous posts, That Blog has covered properties of soil, such as soil types and soil pH. One property not yet written about is soil looseness.

Good soil, gardeners say, should resemble chocolate cake – in both its color and its crumbliness. Good soil has lots of air in it. Why?

First, because these channels and pockets of air also serve as pathways and holding places for water. As discussed in the previous post, we want water to move down into soil. Loose soil structure helps that to happen. Soil that is dense and hard will resist water, leaving it pooled on the surface, where it will either cause flooding, or run off to cause flooding somewhere else.

Second, because the air spaces in soil provide room for roots. Plant roots grow easily through loose soil. Under these conditions, plants are able to find nutrients, absorb water, and anchor themselves securely. In contrast, roots struggle to penetrate soil without air, leaving the plants sickly and weak.

Soil without air is compacted soilSoil compaction is events and processes that lead to compacted soil.

What kinds of things cause soil compaction? One major perpetrator is development: covering soil with pavement is, of course, not good for the soil. Another cause is heavy vehicles. A bulldozer or brush hog may be the fastest way to clear a site of unwanted vegetation and prepare it for new plantings, but these huge machines also cause serious damage to the soil on the site, making it more difficult for the new plantings to get a start in life.

Even lighter vehicles are tough on soil. ATVs can cause compaction and damage, which is one reason some people oppose the use of ATVs in natural areas. And finally, a person on foot is heavy enough to squash down soil and destroy those crucial air pockets.

For this reason, treehuggers may want to curb their desire to hug trees. When we walk up to a tree’s trunk, we are stepping on its critical root zone – the area directly under the tree’s canopy, where its roots are most actively performing their vital functions. Compacting the soil in this area can be very detrimental to a tree’s health. While some tree species – such as those that have evolved to live in perennially soggy areas – are adapted to compacted soil and able to withstand those conditions, many other species suffer from the suffocation of their roots.

Humans like hugs. Trees are indifferent to them. In a few weeks, That Blog will look at simple things tree lovers can do that trees will really appreciate.

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What is soil compaction?

What should we do with water?

The availability of clean water is becoming an increasingly pressing problem in many parts of the world, including some areas of the United States. We need water; we also need to be mindful about how we use it.

Many practices in conventional American yards are not water-wise. We plant grasses that are not suited to our local climate and, in some parts of the US, shower them with twice as much water as is used for the people in our household. We do this sprinkling un-carefully, letting the water splash onto sidewalks or evaporate directly into the air. We point our downspouts onto paved surfaces, diverting precious rainwater to areas where it will do nothing but contribute to street flooding.

Permaculture practitioners have five better ideas for how we should manage water on our land.

Slow it. As water comes onto our property, we want to slow it down. If we let it move quickly, this valuable resource will continue straight on to someone else’s property, likely taking good soil with it. Our loss, our neighbor’s gain. It is to our benefit to hold on to as much free water as we can.

Spread it. Water is a powerful force, and too much of it in one place can lead to unhelpful outcomes. We want to spread out the water instead of letting it pool in one area. We can do this by observing how water moves on our property, and then making small adjustments to change its flow.

Sink it. The best place to put water is in the soil. Soil can hold a tremendous amount of water, and when water is in soil, it is a beneficial, rather than a destructive, force. Once we have slowed the water down and spread it out, it will naturally seek to move downwards. This is good.

Store it. Of course, it is also handy to store water in a form that we can access whenever we need it. Rain barrels or cisterns can hold many gallons of water, fill quickly in even a modest rainstorm, and provide us with a source of water in times when rain doesn’t come.

Share it. In line with the three pillars of permaculture – Earth Care, People Care, Fair Share – we are not slowing, spreading, sinking, and storing water in order to hoard it for ourselves. If the water is in a tank, we can and should share it with those who don’t have enough. If the water is in our soil, we can share the produce that grows from it. There is enough water to go around, if we use it mindfully to take care of ourselves and others.

 

As you follow these principles, be aware of your water rights. In some parts of the United States, it is not legal to divert water from following its natural course downhill onto your neighbor’s property. If you live in the western part of the country, you may be limited to only small changes in your water management, or you may need to work with neighbors to agree on how water will be shared.

What should we do with water?

What is green manure?

Is it a euphemism for plants someone views as being comparable to excrement? Not at all. Green manure is a valuable resource closely related to green mulch.

While there are plenty of contexts in which manure is not desirable, it is good in the garden: it is an excellent fertilizer, providing the nutrients plants need, while not involving any of the environmentally-harmful industrial production processes associated with artificial fertilizer. It is this positive aspect of manure that the phrase green manure refers to.

But what exactly is green manure? Quite simply, it is plants that have been uprooted and lain on or plowed into the soil. Essentially, it is the practice of composting in place. Instead of pulling plants, bringing them to a compost pile, waiting for them to break down, and then carrying the resulting compost back into the garden, the organic material is simply placed where the compost is wanted, to gradually break down and return its nutrients to the soil.

That is, of course, how the process works. Plants are made out of exactly the stuff that other plants need (even more so than animal droppings), and when a plant is no longer alive to hoard and use those resources, it passes them on to other plants. Thus, green manure is the perfect fertilizer in terms of its effectiveness in providing nutrients to plants – as well as being cheap, abundant, and readily available without the need for manufacturing or transportation.

Pretty much any plant can be used for green manure. We can cut down the stems of plants that have died back (after insects are done overwintering in them) and use those as green manure. We can pull weeds and use them as green manure (though we should take care to educate ourselves about which species will simply take this as an opportunity to spread themselves around more). Or we can cultivate plants that are especially good at being green manure.

Two characteristics make a plant suited to this role in the garden. First, the plant must either spread rapidly – so the gardener can harvest some individuals for green manure and still have plenty of living plants to continue reproducing themselves – or the plant must regrow rapidly, so that it can survive having its leaves harvested on a regular basis. (When a gardener cuts down a plant, uses the leaves and stems for green manure, lets the plant regrow, and then harvests it again, that’s called chop and drop.) Second, a great green manure plant is a dynamic accumulator.

What is a dynamic accumulator? All plants pull nutrients from the soil and incorporate them into their bodies. But some plants are especially good at finding and absorbing nutrients. When these plants are used as green manure, they are similarly talented at making nutrients available to the next generation of plants.

As one example, many permaculture practitioners cultivate a plant called comfrey for its value as green manure, as well as its many other uses. Comfrey is not native to North America, though, so those who strive to be native plant purists may prefer to find another species to provide this valuable function.

What is green manure?

What is green concrete?

People who are knowledgeable about the environmental importance of gardening choices sometimes refer to lawns and geometrical hedges as green concrete.

These types of plantings share certain visual similarities with regular concrete: they are flat, square-cornered, uniform in color, and unchanging. They also have some ecological similarities: like concrete, lawns are not very effective at absorbing water, cleaning the air, providing habitat for wildlife, moderating the local temperature, or performing other ecosystem services.

In fact, by some measures, lawns are worse for the environment than concrete. How is this possible? The answer is maintenance.

Concrete is environmentally damaging to produce and install. Once in place, however, it more or less just sits there until the end of its lifespan. A lawn, on the other hand, has little impact while it’s being planted, but then consumes a steady supply of water, fossil fuels, and toxic chemicals in an unproductive cycle of maintenance that can continue for many, many years.

It is worth considering: if you own a home for thirty years and mow the lawn every week, what will you have to show for it at the end? Will you look back with pride that for three decades, you prevented grass from growing? If the answers to these questions are unsatisfying, it may be time to consider alternative gardening practices.

What is green concrete?