Sandy Soil - Strategies to Help offset the Disadvantages

Judy (from Yakima, Washington) emailed me with more information about the soil at her new place.

She said it’s sandy and doesn’t “look” like there are any nutrients in the soil. They plan to work the ground deeply with a tiller and know that it will take a lot of organic material. The property has plenty of beautiful trees for leaves and a large lawn, so she’ll have plenty of organic material come fall.

Sand Soil/Clay Soil

At my first garden I had heavy clay soil. It was fabulous after I improved it and held nutrients like crazy which is the nature of clay.

The upper part of my current garden has extremely sandy soil. After being here for almost 15 years it’s greatly improved because of all the organic material I’ve incorporated, but it’s still on the sandy side.

A Disadvantage of Sandy Soil

One disadvantage of even improved sandy soil is that it has more air in it than clay soils. This causes organic matter (which is decayed organic material) to diminish at a rate more quickly than most gardeners would like.

I usually add lots of organic material each fall but by early summer those particularly sandy beds seem to me to be nutrient poor and even loose water more quickly than those at the lower end of the garden where the soil is more dense.

A Strategy that Helps slow the loss of Organic Matter

If I need to add compost to those beds when I plant, I no longer incorporate it into the soil but rather lay it on top. Then I add a layer of straw or pine tags on top of that. That way the organic matter seeps down more slowly and lasts a bit longer.

I use to scratch the compost into the top few inches, but found that to be a waste because it disappeared so quickly. I saw a noticeable difference when laying the compost on top instead.

Cover Crops Make a Huge Difference

Cover crops are great to enhance any soil, but they make a huge difference in the performance of sandy soils.

Legumes and what they do

Legumes (beans, peas, cows peas, clover) are great crops to boost nitrogen in any garden. Nitrogen not used by your various vegetables drains away quickly in off season — especially in sandy soils. If you plant a legume crop it will absorb nitrogen from the air and store it in tiny root nodules. This is called “nitrogen fixation”. One of these crops grown in the fall or early spring and then turned under or laid on top will provide most all the nitrogen any following crop might need to flourish.

Buckwheat – Another cover crop that’s easy. (Non-legume)

I would urge Judy to plant an easy crop of buckwheat sown thickly into many of the prepared beds this spring. I recommend the buckwheat because it’s fast growing and can sometimes be ready to pull, cut or incorporate in 4 or 5 weeks.

The buckwheat will take up nitrogen and other nutrients from the soil and store them in its biomass. She can cut or pull it just before it starts to seed and lay it back on the soil covering it with straw. (This is what I do rather than turn it under — since my soil is sandy.) The biomass will return nitrogen and other needed nutrients to the soil as well as improve soil structure as it decays. (I’ve been very pleased with the results I’ve had.)

If she turns the biomass under she should wait about 2 weeks or so before planting another crop because the soil life will be using some of the nitrogen to digest the biomass . By laying it on top, she can plant into the bed without worrying that her vegetable plants will be deprived of the nitrogen that the soil life is using to break down the biomass of the cover crop plants.

Other Cover Crops

All cover crops increase the activity of soil life. The more active the soil life — the healthier your soil will be.

An example with oats:

I planted oats in a few of my beds last fall — giving it time to get established before the cold set in. It didn’t winterkill until January! I had intended to cut the dead biomass and lay it on top — leaving the roots to decay by themselves. (It’s my understanding that the soil life activity is greatly increased by decaying roots of the cover crops in the soil.)

When I got out there — for some reason I just felt like pulling it up to see what was going on. I was really amazed at the difference in the soil there. (Also – lots of earthworms where there had not been any in the fall.) Pulled the plants and laid them on top of the soil and covered with straw. Have been delighted with the results I see so far. Can hardly wait to plant some cukes or squash in those spots.

Just so you’ll know –
Some cover crops (rye, oats, and sorghum-sudangrass are the ones I know of) produce a chemical that can inhibit seed germination at least for a while. (It’s called an allelopathic effect.) If you plant seeds into soil that has recently grown rye, oats, or sorghum-sudangrass — the seed may not germinate. You’ll be fine if you plant seedlings however. Recommended waiting time after incorporation into the soil is about 2 to 3 weeks.

Final Thoughts

Keep in mind these cover crop strategies work for clay soil as well as sandy soil, it’s just that sandy soil “needs” them even more.

If you have sandy soil like Judy and I do — try these strategies and let me know how they work for you.

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Related Posts:

3 Things of Primary Importance When Starting a Garden — tells about how I improved clay soil

Cover Crops – Garden Information – Staying Out of Overwhelm

Cover Crops – Your purpose determines when you cut or incorporate into the soil

Crop Rotation – Your Garden too Small to Rotate Crops – Cover Crops are the Answer

Cover Crops – Benefits – Some easy ones

Cover Crops – Buckwheat is One of the Easiest

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