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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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May 06

Soil Woes? Compost to the Rescue!

Posted on May 6, 2015 at 1:12 PM by Ann Vallee

by Christina Mountanos 

 Sharpei contributing to soil compaction issues
My shar-pei contributing to soil compaction issues
I have to admit there are several areas of my garden that I’ve been neglecting over the past few years. The biggest problem? Hard, lifeless soil. The worst is an especially unattractive, narrow area next to my back fence.

What bothers me the most about this particular area is the rate of infiltration (how quickly water enters the soil). It’s incredibly slow. Countless times last year I can recall hurriedly trying to hand water the area after a long day at work, literally drowning the poppy seedlings there while impatiently waiting for the pooling water to soak in. No matter the setting on my shut-off nozzle, it seemed, I found myself constantly stuck in the same routine: flood, wait, repeat.

Fortunately, I was motivated to make a change after attending a Bay-Friendly Landscape & Gardening training and learning about organic compost. Prior to the training, I was already familiar with soil amendments and how they can improve water-holding capability; however, it wasn’t until I learned about soil and compost in much more detail that I became rather excited about the process.

Firstly, what makes good soil? What makes it different from dirt? The difference is simple, yet impactful: life. More than just a collection of granular particles, good soil is teeming with all kinds of living organisms, bacteria, and fungi—an entire ecosystem, really. All these organisms work together to decompose organic matter, fix nitrogen from the air, and ultimately release nutrients into the soil, which plants then use to grow and thrive. By amending your soil with organic compost (which contains organic matter), you’re essentially feeding these creatures. In turn, nutrients vital to plant health are made available for uptake by the plants.

 soil critters
 Soil critters
Good soil also has lots of holes in it (called pore spaces). Pore space is vital to good soil because it provides a place for air, water, and roots to go. It’s also responsible for water-holding capacity. From a biological perspective, increasing pore space can again be connected back to microorganisms. As these creatures process organic matter throughout their lives (and as they die), something called “humus” is produced. Humus is a magical substance that binds to soil particles and improves structure. In the case of clay soil, where the particles are very tiny and often pressed together tightly, humus helps create more pore space between them.

In my particular problem area, I knew two things: I wanted a relatively drastic change and, after receiving the last bit of winter rain, I had to get to work before the soil started meeting the Medusa-like gaze of the afternoon sun again. For unplanted areas (like mine) that haven’t been amended previously, or aren’t regularly amended, organic compost can be dug down and mixed into the native soil. The back of the bag I purchased suggested 6-8 inches, but my local nursery encouraged me to dig the compost down as far as I could.

For established planting areas where it’s best to avoid disrupting the root zone by digging, compost can simply be layered on top of the existing soil just like mulch. Such an application would ideally be done in the fall to let winter rains naturally distribute the nutrients down into the native soil, but really any time of year is a good time for compost! Water from irrigation and worms will slowly distribute the organic material down into the soil, too, just more slowly. For reference, one 2-cubic-foot bag of compost will cover a 12-square-foot area, 2 inches deep. (Good news: MMWD's organic mulch rebate includes compost, too, meaning you can get up to $50 toward your purchase.)

However you choose to do it, adding compost to your landscape is quick and easy. It’s the ultimate remedy for a wide variety of problems, a fix-all for soils that absorb water too slowly and also for soils that may fail to hold water well at all. Improving the rate at which soil accepts water means less water wasted to runoff. Soil that retains water for longer periods of time means having to water less often. And don’t forget that at the root of these qualities is life. Fostering it results in both improved plant productivity and water conservation. You won’t be disappointed.

Happy spring,



Direct Compost
July 27, 2016 at 11:01 PM
Great post.Thanks for sharing great information about composting.

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