On Episode 144 of the Garden Basics with Farmer Fred podcast, we talked about some easy ways to improve your soil, including leaving crop remains (the roots) and topping the garden beds in the winter with shredded leaves from your trees. Also, we talked about how adding wood ash to your garden can change the pH of your soil (bottom line: know your pH).

One warning about adding leaves to the top of your garden bed to improve the soil, from organic gardening professional, Living Resources president Steve Zien: this will only work if you have a healthy soil to begin with.

So, the question arises: how do you start to get a healthier soil? Zien responds:

“Don’t have an organic garden? Leaving crop residue and leaf mulch on the soil surface will still be worthwhile. Mulch and crop residue protects the soil from nature’s forces of wind and water, reducing erosion and the impact of raindrops on bare soil. When a raindrop hits bare soil it loosens the sand, silt and in particular clay particles and moves them around in a way that results in the creation of a hard crust that seals off the soil restricting the movement of air, water, nutrients and biology from entering the soil. Crop residue and mulch also conserves moisture, reduces the need for irrigation, prevents weed growth and insulates the root zone from heat and cold creating a more favorable environment for beneficial soil biology and your plants roots.

When the crop residue and mulch break down and enter the soil, nutrients and organic mater become available to an ever increasing abundance and diversity of soil biology known as the soil food web. These organisms nurture your plants while protecting them from pests. They also glue and tie individual soil particles (sand, slit, and clay) to create favorable soil structure with a diversity of pore space sizes. Small and medium size pores hold on to water that will be available to soil biology including plant roots. Large pore spaces drain providing life- giving oxygen while serving as place for plant roots to grow. Have a heavy clay soil? Only a healthy soil food web that can create and maintain soil structure will open up that clay soil, allowing water to penetrate into and percolate through the soil.

The goal of every gardener should be to create a healthy soil food web that will yield the most productive and nutritious foods and beautiful landscapes. Leaving crop residue and mulch on the soil surface is just one technique to accomplish this goal. Regularly applying compost and worm castings to the soil surface not only supplies additional soil biology but organic matter, the energy source for the soil food web. It is also important to minimize soil disturbance (cultivation, tillage) that reduces both the diversity and abundance of soil life.

One must also realize that soil organisms are destroyed by synthetic fertilizers and pesticides, therefore their use must be eliminated or at least minimized. One should only use organic fertilizers, ideally following the recommendations of a soil test. Rototilling the soil, using a synthetic fertilizer or pesticides will only be a step backward in creating a vibrant and resilient soil food web.

The sooner and more completely you adopt these practices (among many other regenerative soil practices) the faster you will create a healthy soil food web with good soil structure and an abundance of organic matter capable of producing the garden and landscape you dream of.”

We are hopeful Mr. Z shares with us in the future those “many other regenerative soil practices”.

Below the paywall:

• Understanding soil pH levels (with nifty charts)

• Is wood ash right for your garden? (Depends on your current soil pH)

• The danger to your garden soil of too much wood ash.

• Soil pH test kits

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Know Your Soil pH

Blame the Danes if when the garden conversation turns to “pH” - a term that translates as “potential Hydrogen” - your mind wanders to thoughts of social media posts of kittens riding a Roomba.

According to the UC Master Gardeners of Napa County: “In 1909 Danish biochemists decided to use pH as shorthand for potential hydrogen. They developed a pH scale, ranging from 0 to 14, to represent how many hydrogen ions (H+) are present in a sample. According to the scale, distilled water is a 7 (neutral). Anything under seven is considered acidic (sour), while anything above 7 is alkaline (sweet).

“These values are not linear but, rather, logarithmic. That means that a sample with a pH of 6 is 10 times more acidic than a sample with a pH of 7.

“What does pH have to do with gardening? Everything. A soil’s pH affects the ability of plant roots to absorb nutrients and water. Most minerals in the soil must be dissolved to be absorbed by a plant’s roots. Soil that is slightly acidic (6.2 to 6.8) or slightly alkaline (7.4 to 7.8) will dissolve minerals the best.

“When soil is too acidic (pH below 5.5) new foliage looks yellow, distorted and possibly black around the edges and the plant does not grow. When soil is alkaline (pH above 8), plant leaves may look yellow between the veins or have a bleached or mottled and blotchy look. New growth may have brown or black leaf tips.”

On the above chart, note how some elements, such as iron, become less available to plants as the pH rises. “Less available” doesn’t mean the soil is missing that element; it just means the plant isn’t able to uptake it because of the existing pH level.

In discussing the use of wood ash in the garden with college horticulture professor (retired) Debbie Flower, also on Episode 144 of Garden Basics, she pointed out to know your soil pH before you add any wood ash. Wood ash is highly alkaline and can throw your soil out of whack if your soil is already teetering on too much alkalinity (at or above 7.0).

Scenic Bypass: Is Wood Ash Right for Your Garden?

Ed Perry, retired Stanislaus County (CA)-based UC Farm Advisor, has the answer to that question. And of course, the answer is, “It depends.”

Plus, it depends how much wood ash you added to the garden. Too much can lead to trouble. Never use the ash from charcoal briquettes in a garden. The ashes of manufactured coals may contain too many extraneous ingredients, such as binders and lighter fluid, which can be detrimental to your soil.

“Wood ashes contain chemicals which are very alkaline with a pH of 10 to 12,” explained Perry. “They are harmful at high rates, especially in soils that are already alkaline. Since about 80 to 90 percent of wood ashes are water-soluble mineral matter, high rates can cause salts to build up in soils resulting in plant injury.”

To limit problems of excess salinity, alkalinity, and plant nutrient availability, Perry recommends no more than 5 pounds of wood ash per 100 square feet, scattered on freshly tilled soil, and raked in, once per year.

In his publication, “Wood Ashes as a Garden Fertilizer”, Perry points out that in general, wood ashes contain five to seven percent potassium and about two percent phosphorus. They also contain 25 to 50 percent calcium compounds. The presence of phosphorus in a fertilizer encourages flowering and fruiting.

Chances are, that wood ash bucket you’re hauling out of the house is holding more than five pounds. Try scattering it evenly across a surface, 10 feet by 10 feet, and you will see how difficult it is (especially if the wind is blowing) and how thin the final layer must be on the soil surface.

Perry warns gardeners to avoid contact between freshly spread ashes and germinating seeds or new plant roots by spreading ashes a few inches away from plants. Ashes that settle on foliage can cause burning. Prevent this by thoroughly rinsing plants after applying ashes.

Because ashes are alkaline, avoid using them around azaleas, camellias, and other acid-loving plants. Wood ashes are very low in nitrogen and cannot supply your plants’ needs for this element. You will need to follow your normal nitrogen fertilizer schedule when ashes are applied.

Too Much Salt: It’s Bad for Your Garden, Too.

The University of California Cooperative Extension in Ventura and Contra Costa Counties have publications on this topic, as well. They repeat this warning about using wood ashes in the garden: “A further compounding problem is that about 80 to 90 percent of the minerals in wood ashes are water-soluble, so that high application rates can cause salts to build up in soils, resulting in plant injury.”

However, there is one nugget of potential usefulness about using wood ashes in the garden. According to the Butte County UC Master Gardeners, dry ashes, or other abrasives such as diatomaceous earth can be used as barriers for slugs and snails. Such abrasives should be piled about one inch high and 3 inches wide to be effective. However, these materials lose their deterrent value if they become damp, making them not very useful in most garden situations.

Meanwhile, Back in the Vegetable Garden…

Here’s a list of the preferred pH range of many garden vegetables, from the University of Nebraska:

Which pH Test Kit is Right for You?

About pH test kits: they run the gamut of price and quality. Among the easiest and most widely available are the inexpensive pH test kits found at nurseries, online, and home supply stores, such as this from Rapitest. A step up, but subject to fluctuations and durability issues, are the pH meters that are available (you get what you pay for!). For more accuracy, consider the LaMotte test kits, which also give rough measurements of nitrogen, phosphorus and potassium content, along with 2 booklets that are very educational.

TRANSCRIPT - Steve Zien on Easy Cool Weather Soil Improvement Tips

Farmer Fred

Well, we’re going from summer gardening to cool season gardening and maybe you don’t want to put in cool season crops. Maybe you don’t want to deal with plants that might be killed by a frost or freeze. But don’t leave your summer garden intact. In its place, there are some cheap and easy things you can do that will not only minimize pest problems for the following years, but also during the winter, feed your soil and make it even better for next year. We’re talking with Steve Zien. He is Sacramento’s organic advocate. An organic gardener for decades. He ran his own organic gardening and consulting company for decades. And Steve, I know we’ve talked about cover crops before, but going beyond cover crops. If people want an easy way to feed their soil during the winter, and they don’t want to grow cool season crops... I think one of the easiest things to do, well two things to do, is a cut down everything to soil level. If you’re growing tomatoes and peppers, just cut them off at the soil level, but leave the roots in the soil and then cover that soil with leaves that are falling from the trees in the fall, grind them up with your mower or a weed whacker or something and just put down six-eight - twelve inches of leaves on top of that garden bed.

Steve Zien

Yeah, it’s absolutely wonderful. It regulates the soil temperature, the soil temperature will be warmer. The fact that it’s all ground up makes it easier for the biology that’s in the soil to come up into that mulch and munch it down. And then the rains will help leach those small little particles down. The worms that are in your soil will come up and feed on that every single day. And you know if it’s a thick mulch, even at night, because it’ll be dark and they will be aerating your soil and and taking that organic matter of material down into the soil. And the nutrients that leach through by the rains will also leach the biology because that’ll start composting on the top of the soil and the biology that’s compost then will increase in numbers and will end up moving down into the soil as well. So you will get nutrients move down into the soil and increase the nutrient value and you will get more soil biology. And the more soil biology you have, the more diversity, the more numbers, the healthier your soil is and the healthier your crops will be. I just took a class recently, everybody has been talking about rotating your crops for decades to reduce pest problems. And they’re saying that if you have the right biology and you put down you know, you either grow cover crops or you put down a thick mulch, you really will have the biology in there, the beneficial soil biology to naturally combat the pest problems and you should not have to rotate your crops.

Farmer Fred

I love it when you’re a contrarian. And, it makes perfect sense, too.

Steve Zien

Yeah, if you’ve got the good soil biology down there. And then you’re feeding it with either a cover crop or with a thick mulch, you’re feeding though that good biology. And so the good biology will fight it out basically with the bad biology and not allowing them to grow in substantial numbers, where they could do harm to your plants the following season.

Farmer Fred

Now I mentioned earlier about clipping off the tops of the plants and leaving the roots in place, true or false.

Steve Zien

True. Because they will decompose and typically will decompose pretty fastly. Again, that’s if you have an organic, happy, healthy soil. If you’ve been using pesticides, you’ve been using synthetic fertilizers, the biology isn’t going to be there to break that stuff down. But if you are growing organically, you’ll have a lot of biology in your soil that stuff most of those roots will break down very very quickly. And they will create air channels there and they will end up aerating your soil. Because where the root was, there’s nothing there anymore. And so you’ve got these big pore spaces. So when you irrigate next spring, the water’s gonna move in through the soil, the worms can move through the soil better, the soil biology can, you know, all of the various you know, microbes and beneficial mites and protozoa and all those guys can move through the soil and do their job better.

Farmer Fred

And you’re also improving water percolation for the years ahead by keeping those roots in.

Steve Zien

Exactly. Because they will decompose. The biology will basically reduce them to nothing. And there will be large, large pore spaces where those roots were and so when you irrigate, the water will go down very, very nicely, which is important. If you’ve got a clay soil, and at least here in the Sacramento region, most gardeners have a clay soil.

Farmer Fred

I think across the country, there are a lot of gardeners who are dealing with clay soil. Yes. You mentioned a very unusual word here. I’m not sure what it is. You’re talking about to help that mulch layer on top break down, that “rain” could do that. What is this thing called “rain” that you’re talking?

Steve Zien

I don’t know. It’s been a long time. And you know, in the last year we got what, seven inches, something like that.

Farmer Fred

Yeah. Now that brings up a question if it doesn’t rain. Man, I hope it rains, but if it doesn’t, this fall and winter here in California and in many areas of the West, if you don’t get the fall and the winter rain, should you irrigate the top of that mulch, like once a week? Just turn on a hose and start sprinkling it?

Steve Zien

I think it would be a good idea once in a while. Certainly, once a week it’s not necessary. Typically, if you do it once in the wintertime, it’s not very hot. In many cases, it will hopefully be cloudy. Make sure that mulch is moist, not wet, but moist when you put it down or after you put it down. And then, before you add more moisture, don’t just look at the surface, dig down an inch or two and see if it’s dry. And if it’s dry, then you might want to add more more water.

Farmer Fred

Alright, it’s a good point. And to reinforce something we said earlier: the smaller the pieces of those leaves that you’re using as mulch, the better the quicker we can break down and feed the soil. And plus, if you’re just stacking 12 inches of unchopped leaves on top of your garden bed, you might create an anaerobic environment.

Steve Zien

It would help to grind it up some way. And you know a lawnmower works well. And you mentioned that another easy way to do it if you’ve got a string trimmer is get like a five gallon or get a garbage can and put a small amount of the the mulch in the garbage can and then run your weed eater down in there and it’ll chop it up pretty nicely as well. It’s an alternative way to do it.

Farmer Fred

And to save wear and tear on that garbage can make sure it’s a metal garbage can, which are still available. They’re out there. Yeah, usually a 27 or 32 gallon metal garbage can and then put those whole leaves in, like you said, maybe fill up that can 1/3 and then put your string trimmer in and turn it on, whirl it around a while and you’d be surprised at how the level of leaves drops. And then you can pile more in there and then chop it up again and just do it in increments like that.

Steve Zien

Yeah. And make sure you have a string trimmer. I know on some string trimmers, you can put like metal blades on them. That’s gonna pretty much destroy your container.

Farmer Fred

Yeah, and wear eye protection anytime you do that. And string trimmers, not even the plastic blades. The string trimmer is best. Yes. If you’re not going to be planting cool season crops this year, then the least you can do for your soil is cover it with mulch, chopped up leaves is great. Just leave it on til spring and you don’t even have to remove it in spring. You can just move it aside and plant whatever you’re going to put in come springtime and keep that as a permanent mulching area. Just make room for your plants.

Steve Zien

Exactly.

Farmer Fred

Mr. Exactly is with us. Steve Zien, Sacramento’s organic advocate, of Living Resources Company. Steve, thanks for the good cool season advice.

Steve Zien

It’s been a pleasure as always, Fred.

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Fred Hoffman is also a University of California Cooperative Extension Master Gardener in Sacramento County. And he likes to climb (and descend) on his bike.

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