It’s true that we reap what we sow in the garden. It is also true that the more we reap, the more we need to give back to the soil.
Natural gardens capture sunlight and water to grow a lush, verdant paradise in our backyards. Underneath it all, this process is driven by a living, breathing soil.
Microorganisms, fungi, worms and other critters below ground transform soil itself into garden vegetables, flowers, shrubs and trees. When plants die, they return to feed the millions and billions of soil critters. In this way, the natural garden system can take care of itself for a very long time.
Unfortunately, the best-intentioned gardener can sometimes get in the way. When we harvest, weed, rake or trim gardens and landscapes, we remove the organic material that feeds the soil. Some of this is unavoidable.
Without a doubt, I want to eat the sweet corn, tomatoes and kale I worked hard to grow. Sometimes, I need a smooth garden bed to plant delicate seeds. If noxious weeds take residence in my garden, I’m going to root them up and throw them out.
At other times, we take from the soil without really thinking about it. Bagging lawn clippings or raking leaves removes food that the living soil needs. Leaving soils uncovered and bare starves them and risks damage from wind and water.
The easiest way to grow lush, living gardens, therefore, is to copy nature as much as possible. To feed our plants, we want to feed our soils. We do this by giving more than we take: the golden rule of gardening.
Keep it local
In the lush Northwest, there’s a wealth of soil food right at our fingertips. Many of us turn to bought or imported compost and manure. The easiest way to feed the soil, though, is to use what’s most readily at hand.
Before I look to outside sources, I look in my own backyard. Green grass clippings, chipped freshly pruned branches from trees and shrubs, fallen leaves, and garden plants themselves provide a nutritious and delicious soil feast.
I’ll add these back to the soil by tilling them in the garden or simply layering them on the soil surface as mulch. If mulching, keep green clippings and chips under a top layer of leaves or straw to maximum nutrients. If turning organic material into the soil, make sure to give it time to decompose before planting.
Oregon abounds with creative, ecologically minded businesses. In your neighborhoods and communities these can also provide garden food. To supplement your own supply, talk to local restaurants, food processors, cafes or breweries. Add food waste, coffee grounds or spent brewer’s grain to compost, sheet mulches or tilled garden soils. Some of these high-nutrient materials, like coffee grounds, fertilize gardens as well. Creatively transforming neighborhood “waste” into garden vegetables is one of my favorite ways to recycle.
Keep them covered
A bare soil is a hungry soil. Keep soils well-fed by covering them with mulches or living plants. In addition to providing food for the living soil, covering the soil also provides shelter, keeping soil life comfortably moist and protected so that it can stay active.
In the Northwest, soil cover is especially important to absorb heavy winter rains. Good mulch allows water to sink into the soil instead of running off the surface and eroding precious topsoil.
Clay soils in the early spring are one exception to this rule. To warm these cold soils up, pull back the mulch for a few weeks to get a jump on spring planting.
Save the nutrients
If you’re a gardener in the Northwest, you’ve probably heard of “leaching”. This is the process, every year, by which winter rains wash precious nitrogen out of soils. Because nitrogen is the key ingredient for green and growing gardens, we want to save it for the next season instead of letting it leach away.
To keep nitrogen in my garden, I use two simple strategies. First, I save nitrogen fertilizers for the spring. Generally speaking, I start soil preparation in the autumn by adding soil food, organic supplements, and lime in advance of the spring rush.
To avoid leaching winter rain, however, I save nitrogen-rich fertilizers, including fresh manures, for the spring. If added in the fall, there’s a good chance winter rain will flush mobile nutrients right out of the garden.
Second, I catch nitrogen in living, garden plants. Not only does a living cover protect the soil, it also stores soil nutrients in the plants themselves. Over the winter, fall-planted cover crops or over-wintered vegetables take up nitrogen to keep it from leaching away.
Let them breathe
I’ve mainly focused on feeding the living soil, but like all living things, soils also need air to breathe. Waterlogging or compaction squeezes the air, and the life, out of soils. Luckily, organic soil food, by fluffing up a soil, also prevents waterlogging and can remedy compaction, even in notoriously difficult heavy clays.
After a rainy Oregon winter, wet spring soils are also particularly vulnerable to compaction. For soils to breathe, we want to avoid this at all costs.
Though dirty mud boots may symbolize Northwest spring gardening, to prevent compaction, avoid the temptation to work, till or even walk on wet spring soils. With a little care and feeding, your soils with thank you with increasingly bountiful gardens over the years to come.
— Elizabeth Murphy
Elizabeth (Ea) Murphy is a soil scientist and author of “Building Soil: A Down-to-Earth Approach” (Cool Springs Press, 2015). Since 2006, she has owned a half-acre garden in southern Oregon, which she considers her laboratory for experimenting with sustainable soil management and gardening practices for landscapes and vegetables. She shares her experience as a former agricultural extension agent and faculty instructor for Oregon State University Extension’s Small Farms Program, where she taught and consulted with gardeners and farmers about best management practices to build healthy soils. Learn more at the soil science researcher and passionate gardener’s blog, dirtsecrets.com.
Published by Oregon Live