What to Add to Your Soil in the Fall (Before Winter Sets In!)

We’ll let you in on a little secret that it take many gardeners a few years to figure out: Soil is the bedrock of any successful garden and late fall is the best time for soil-build for next season.

What is Healthy Soil?

Remember soil is not dirt. Soil is live organic matter teeming with microbial life!

Organic matter can be in the form of compost, manure, fallen leaves, or a cover crop, which we’ll discuss more below. Isn’t it convenient that nature gives us all those autumn leaves at the end of our harvest season? This is why fall is such a good time to add nutrients back to the soil. 

Adding organic materials in the fall allows time for them to decompose and break down over the winter. Soil high in organic matter releases a reservoir of nutrients that are slowly released over time, which improves root growth and biological activity.

Reconsider Tilling in the Fall

If you have a small garden or a raised garden bed, consider leaving the soil left untilled. All that tilling does is disrupt soil structure, create more erosion, and kill earthworms.

• For a small garden, simply dig by hand to remove any weeds, old plants, and debris. 
• Then add organic matter but simply add a layer on top and you can turn the soil lightly with a garden fork to mix it in.

Now, if you have a large garden, digging up all your weeds and old plants may simply be too much work. In this case, add organic matter before you till, and then consider covering the soil with some form of mulch to avoid erosion.

Cover the Garden

How often do you see bare soil in nature? Not very often. And there’s a good reason for this. Bare soil is easily eroded by wind, rain, snow, and weather elements—washing away all the nutrients. 

In the garden, covering the soil during wintertime offers a number of benefits. It gives weeds a tougher time of it. By using organic matter such as compost or manure or leaves, you’re gradually feeding the soil—specifically, the life within the soil. This, in turn, feeds the crops you grow in it.

So, what’s the best way to build the best possible soil? You don’t needn’t to buy expensive soil amendments; much of the way you improve the soil is free or very cheap.

Here are a few ways to both cover and feed the garden.

1. Compost or manure:

You should be composting almost everything: kitchen scraps, pruning, leaves, cardboard, grass clippings. It’s free! Once you add a good mix of ingredient, you’ll get a lovely compost which is a powerhouse in the garden.

Manure is fantastic as well, but it has to be from a trusted source. You don’t want it contaminated with herbicides which could pass through a horse or cow and inflict damage on your crops.

Add compost or aged manure about an inch deep across your bed to keep the soil covered over winter, weeds suppressed, and worms busy. The worms will drag it down to the soil so the microbes can work on it, too, releasing all those nutrients in time, and feeding your crop for next spring.

You can transport manure in the back of your car; if it’s fresh, stack it someplace for about a year because fresh manure is too strong for most plants.

Image credit: Novakovav/Shutterstock

2. Fall leaves, grass clippings, or wood chips

You can also make use of readily-available organic materials that haven’t rotted down, especially those autumn leaves! Just spread the out onto beds! Learn more about using leaves.

Or, spread wood chips around fruit bushes and it will keep weeds down as well as slowly release nutrients to feed your plants. 

By the way, let’s dispel a myth. Wood chips do not rob the soil of nitrogen. Left on the surface, they create nothing but goodness, similar to a woodland floor.  When you wish to plant, just push the wood chips aside.

3. Field Bean Cover Crop

Another way to build soil is to seed a cover crop which will break down and add vital nutrients and organic matter to your soil. Cover crops also prevent erosion and suppress weeds.  One crop you can always plant is super super hardy field beans. Bury the seeds a couple inches into the soil and they’ll grow until spring. You’ll end up cutting them down BEFORE they produce pods so that they can focus on fixing nitrogen from the air for their roots. When you chop them down, you can put the top growth into the compost heap for a full cycle of soil health!

Image: Cover crops mix on raised garden beds. Credit: WSU.edu

Other examples of cover crops are winter wheat, winter rye, and annual ryegrass. Seed those cover crops are seeded in fall about 6 weeks before the first expected fall frost date. To plant, you clean up any remaining crops and plant degree. Use a garden spreader to broadcast the seed, lightly cover it with soil, and water. Let the cover crop grow until early spring, then till it under. Wait a few weeks after tilling before planting.

See our Cover Crop Guide. 

Get a Soil Test

How do you know if your soil has the right amount of nutrients for excellent plant growth? If you’ve never tested your soil, we recommend a basic soil test every 3 to 5 years. Before you spend all that time growing food, it’s worth finding out if your soil is lacking the right nutrients or perfectly fine!

Soil testing services are offered for free or a small fee by most state university extension services. It only takes a few minutes to take a representative soil sample and send it off.  See how to take a soil test and a list of Cooperative Extension Services to call about a soil test kit. 

Or, see three of simple DIY soil tests for a quick and dirty evaluation of your soil. 

The soil test service will also give you not only the results but alo recommendations and solutions with suggested materials to add to your soil.|

For example, you may need to adjust the soil pH (the soil’s acidity/alkalinity). A proper pH is important for nutrient availability to plants. Most vegetables grow best in soils that are slightly acid, falling between the 6.0 and 7.0 range on the pH scale. Add lime if you need to raise the pH and sulfur to lower it to within these levels. (NOTE: Do not just add lime or sulfur without knowing your pH. This would be detrimental to your plants.) If you burn wood, you can use ashes them instead of lime to sweeten the soil.

A basic soil test usually measures phosphorus, potassium, soil pH, and organic matter. It can take years to get the levels of pH, potassium, calcium, magnesium, and phosphorus in garden soil up to the optimum levels. See more about NPK Ratios And What This Means.

Happiness is a positive soil test, one that lets you know that you have been doing something right. If everything comes back in the optimal to high range, you can happily ease off on applying amendments. Too much of a good thing can do more harm than good.

For example, here are recommendations from a soil test:

1. Nitrogen: Spread 2 pounds of nitrogen per 1,000 square feet using either 33 pounds of soybean meal or 15 pounds of dried blood. I’ll stick to the soybean meal since the idea of dried blood makes me squeamish!
2. Potassium: To maintain the perfect potassium level they recommend using 14 pounds of Sul-Po-Mag to supply 3 pounds of potassium per 1,000 square feet.
3. Phosphorus: Absolutely no extra phosphorus is needed so any commercial fertilizer mix should have 0 for its middle number.

As mentioned above, manure and compost are excellent sources of nutrients but skip the free goat manure this spring if you have home-made compost!

Get on track for a fruitful year in the garden come spring! This should give you a game plan for the necessary action to take to bring your garden up to snuff. Remember: Look after your soil and your soil will look after you!