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Lorraine's Garden, Issue #005 -- Christmas Gifts and Cation Exchange Capacity
December 07, 2013

December 2013 Issue 5

In this issue:

1) Christmas Gifts for Gardeners
2) Five Fun Things to Cure GWB (Gardener’s Winter Blues)
3) Soil Science Lesson: Cation Exchange Capacity: Part 1 (And Why It’s Important)

Christmas Gifts for Gardeners

I came up with a collection of gift ideas that are all practical and useful items for real gardeners. They’re all things that I either own myself, or else wish I did! Rather than duplicate them here, here is a link to go right to the Best Gifts for Gardeners page.

Five Fun Things to Cure GWB (Gardener’s Winter Blues)

Grab a cup of coffee and browse the seed catalogs. Flag every page that has something you’d like to try with a sticky note, and don’t be reasonable! (Yet). This will help reduce GWB when you start missing green things and drooling for the taste of fresh basil on August tomatoes.

Let yourself dream, pretending you have more space (and time) than you actually will come summer. This technique seems to keep GWB away till about mid-January (...sigh), when it’s time to think about switching to actual garden planning, with last years garden map in hand and plant rotations in mind. Then it’s time to start narrowing down and choosing. It’s actually the start of the gardening season, even though it doesn’t feel like it yet! Remember you have more time now than you will once the ground has thawed, so now is a great time to get things well planned-out and get seeds ordered. Choose a few new things from the catalogs, alongside your old standby favorites.

Visit the nearest botanic garden. If you don’t have one, visit the nearest nursery or greenhouse. Or if you don’t have one of those, try the nearest florist or big supermarket that has flowers or growing plants. Take in the colors, the smells, and really look at the miracle of flowers. Take your camera (even if it’s your phone), and get creative with photography. Try some off-center close-ups. Or focus on foliage. Or shoot a cauliflower in the produce section, up close. When you get home, if you don’t have Lightroom, Aperture or Photoshop, download Picasa from Google (free) to crop and play around with your pictures.

Go to the library and check out a book that will make you a better gardener, and read it cover to cover. I highly recommend Carol Deppe’s The Resilient Gardener, Steve Solomon’s The Intelligent Gardener, or Eliot Coleman and Barbara Damrosh’s The Four Season Farm’s Gardener’s Cookbook (a good deal ‘cause it’s really two books in one: a 4-season gardening manual and a vegetable-based cookbook).

Dress up warm and take your camera outside for a walk, on the mission “In Search of Winter Color”. I used to do this on the hiking trails behind Boulder. I’d strap on my mini-crampons and climb those icy trails, where it was mostly all white and brown. But my camera taught me to look deeper, and I found pockets of rich green, bright oranges and reds. When you get home and get thawed out, you can make a digital collage of what you found ( posters are fun to play around with, even if you don’t buy one!). Or don’t even go out, just make an online collage of your favorite garden photos from last summer.

Make some new boards on Pinterest. Start a collection of raised bed designs, or best bean trellis ideas. Find macro shots of vegetables, like cauliflower or broccoli. Look for nature fractals. Find all the best “tips” and save them all on one board.

Soil Science Lesson: Cation Exchange Capacity Part 1 (And Why It’s Important!)

“What the heck is ‘cation exchange capacity’? I see CEC on my soil test results, but I don’t know what it means.”

Roughly speaking, cation exchange capacity can be thought of as a measure of your soil’s overall fertility.

Besides “eating” carbon dioxide, water and sunlight, plants need minerals from the soil to live. Some of these nutrients are dissolved in the soil water and the plants can take them up easily. But if it rains or gets irrigated a lot, these minerals will wash down into the subsoil and be lost to the plants forever.

Soils with high CEC, however, are able to hold onto their nutrients, making the nutrients available to the plants when needed and preventing them from being washed away. How does the soil do this?

Soil Nutrients Meet Soil Particles
All soil mineral nutrients carry tiny electric charges, which can be either positive (in which case they are called ‘cations’) or negative (called ‘anions’).

Some particles of the soil itself are negatively charged, so the positively-charged nutrients (cations) can stick to them and be prevented from being washed away.

What kind of soil particles bind cation nutrients? Soil is made up mostly of:

  • different sizes of tiny bits of rock (sand, silt and clay)
  • organic matter in different stages of decomposition, including humus
  • microorganisms: fungi, bacteria, actinomycetes, nematodes, protozoa, etc.

Only two of these components are capable of binding positive ion nutrients: clay and humus. Clay particles are microscopically tiny bits of mineral rock that have broken down into little platelike shapes. Humus is organic matter that is so decomposed it cannot break down any further.

These two types of particles carry negative charges on their surfaces, and they are what bind the cation nutrients. When cations are bound this way, it doesn’t matter how much it rains - the soil is able to hold those nutrients “in escrow” until the plants need them.

So cation exchange capacity is a direct reflection of how much clay and humus combined you have in your soil, and therefore how much potential there is to bind and hold nutrients.

Cubbyholes Full of Food
Here’s an analogy. Imagine you have a pantry wall made of cubbyholes, which may or may not have any food in them. The cubbyholes represent the cation exchange capacity, and the food in them is like the mineral nutrients.

CEC is very important. You can add missing mineral nutrients by applying the right fertilizer to your garden, but if you don’t have enough exchange capacity, most of it will just wash down into the subsoil and you will lose your fertilizer as well as your money.

The REAL Benefit of Compost
Herein lies the real benefit of supplying good, fully-decomposed compost to the garden. It may provide a little nutrition, but far more importantly it provides the humus - the cubbyholes - that keep the mineral nutrients available to the plants.

Even if you don’t need fertilizer (but I bet you do), the humus and clay hold the nutrients released by the slow wearing away of the parent mineral rock that makes up your soil.

Anion Nutrients
You may be wondering, “But what about the negatively charged nutrients - the anions? Do they just wash away?”

Somewhat, yes. But humus (not clay) has a unique capacity to also hold onto anion nutrients. (Not sure how it does it, but it does.) If you have enough humus in your soil, both cation and anion nutrients will be held and be available to the plant roots when needed.

Summary: Cation exchange capacity is actually a measure of the potential of the soil to bind and hold onto positively-charged nutrients and prevent them from washing away. Soil has this capacity because clay and humus soil particles are negatively charged, and like magnets, they attract and bind positively charged cation nutrients. In addition, humus has the ability to hold anion nutrients, too.

Stay warm, brave gardeners! (And if you're in the southern hemisphere, stay cool!)

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