The Plot Newsletter

Forwarded this email? Join free at the-plotnewsletter.com/subscribe

Hey Reader,

It’s been two weeks since the last newsletter, and it was so hard to not reach out to you last week after the change in publishing schedule. Instead, I’ve spent the extra time working on researching this week’s topic, which includes an insightful interview. Hope you enjoy the new cadence.

The Science of Better Garden Soil

How much do you know about the soil in your garden? Good garden soil is incredibly important, but since it exists in a world hidden beneath our feet, most of us treat it as an afterthought. While digging my new vegetable garden out this spring, I realized that there was so much clay that I could make pinch pots as if I was back in art class. It’s not the best starting point, but we all have to make the best with what we’ve got in the garden.

To learn more about the precious and hidden world of good garden soil I connected with Gregg Sanford, who is a professor at the University of Wisconsin - Madison, and director of the Wisconsin Integrated Cropping Systems Trial, which is a long term experiment to answer questions about organic agriculture. Gregg also has a research project called the Soil Organic Carbon Network which spans Wisconsin, Iowa, and Minnesota. Best of all, he is also a gardener and the perfect guide to help us learn more about improving the soil in our garden plots.

The sections below are paraphrased from our conversation. I learned so much from our discussion, and left with a new appreciation for the humble world of soil. Below is a mix of science and practical advice, for you to improve the literal foundation of your garden.

Know Your Soil Texture:

To make sense of soil physical properties, scientists separate soils into three main textural classes or based on size. The largest is sand, which everyone can recognize from their bum after a trip to the beach. (That last part is from me, Gregg is a respectable scientist after all.) Sand has a gritty and coarse texture.

The next component of soil is silt. Silt is much smaller than sand and feels like flour. It has that same silky texture that you may know from baking. 

Clay is the last component of soil and it is extremely small. You’ve seen sticky clay on the bottom of your boots after a rainy day.

These classes are important because they have different characteristics. For example, sand is super coarse and fantastic at getting oxygen and air into your soil because plant roots need to breathe. It also drains really well, so you won't get waterlogged soils. However, it is not great at holding nutrients. Clay on the other hand is almost the exact opposite. It drains very poorly due to an almost astronomical amount of surface area. Clay does a great job of holding nutrients. Silt is right in the middle. It holds water better than sand and dries out faster than clay.

The Goldilocks zone for gardening is where we have a nice mixture of these, something like a silt loam. There’s a lot of silt, a good amount of organic matter, and a reasonable amount of clay, and a little bit of sand. That's the happy medium. We can go in either direction, and as home gardeners, we tend to be able to manage it because we can irrigate, or we can add amendments to break up heavy clay soils.

Organic Matter Punches Above Its Weight

Outside of soil textures there is loam, which is the organic component of the soil. This organic matter, often referred to as OM, helps balance your garden soil. The addition of organic matter like compost can help retain water and improve your soil texture. That soil texture influences porosity and how dense your soil is, something we call bulk density. Home gardeners know this intuitively, when your soil feels like it has turned to concrete. Organic matter helps you keep a light and fluffy soil texture and reduce compaction.

Organic matter also serves as a food and resource for microbial communities. Bacteria, fungi, and actinomycetes that are living in your soils. These little guys use the carbon in organic matter as energy, which releases nutrients that are available for your plants. Organic matter, despite being a small part of your soil makeup, punches above its weight in an ability to deliver nutrients to plants. 

Gregg’s 5 Practical Tips to Improve Your Garden Soil

• Till less - You want to do things that encourage soil aggregation, which is something that develops over time where microbes work on organic matter and fungal hyphae connect soil pieces together. Every time we till our soil, we disrupt those aggregates and break them up. There’s a time and a place for tillage, but I'd encourage you to avoid using the rototiller every year. It looks good at first, but over time it is bad for your soil structure. 

• Rotate more - Rotating your crops is important for soil, but also to reduce diseases in your garden. Try to move plants around your gardens each year to avoid buildup of soil pathogens that specialize on certain crops. If you have a small plot, then consider raised beds to help rotate crops. 

• Test your Ph - Ph fundamentally affects whether your plants can access nutrients. It can be overlooked unless you are growing Blueberries or Azaleas, but it is essential to plant health. Test your Ph with a meter, and make amendments as needed. Most garden veg likes a 6-6.8 Ph.

• Use Organic Matter - As mentioned above, OM is a great way to improve soil health and nutrient availability. It’s also easy to do right now. You can go to the garden center after reading this, buy a bag of compost, and spread it on your garden soil. 

• Mulch well, and prosper - Mulch your soil to keep it covered. It will conserve moisture, and reduce erosion. Soils are the most precious thing in our garden to maintain, so do everything you can to keep it in good condition.

Field Notes:

1. Over the last couple weeks I weeded my community garden plot, built a fence for my kitchen garden, and sheared an overgrown hedge. We’ve had nice weather for gardening in Madison with temperatures in the 70s.

2. Did you catch our last article? There’s a ton of helpful information in there about how to garden smarter!

3. Looking for more soil science? Read this UMN extension article on promoting healthy soil in your garden.

Plotter’s Commons:

I’m looking for ideas for articles for the rest of the year. Do you want to write one for The Plot or have a question you want answered? Just respond to this email.

Join our Facebook group

Bulletin Board

Olbrich Gardens in Madison, Wisconsin is looking for volunteers for their home garden tour. Come volunteer with me! You don’t need to be a registered volunteer yet to participate. July 10th and Saturday, July 11th from 9-12 in Verona. (Just reply to this email if you’re interested.)

Mary Q. won the raffle this month and won a felt cover for a potted plant! Thank you for supporting The Plot, Mary!

If you’d like to participate in the raffles, then you just need to upgrade and become a Plot Founder. It’s a small way for me to thank those of you who financially support The Plot.

Until next Thursday,
Ken Welch

About the Author

Ken Welch is a garden writer with a very serious degree in Horticulture. When his city lacked a community garden, he helped build one. He teaches new gardeners how to grow their own food.

Watch The Plot on YouTube

Cibus Est Imperium | Food is Power