Soil fertility

Learning from a Soil Test

28 February, 2021 by amygwh

I finally sent off a couple of soil samples to the state testing lab. The soil here is new to me (sand, not north Georgia’s red clay), and last summer’s garden was less productive than I had hoped. Getting a baseline set of measurements will boost my understanding of what the soil needs to produce more good food.

The routine test for home gardens provides quite a bit of useful information, but I also paid for a couple of extra bits, the organic matter content and percent nitrogen. One sample that I sent in (labeled Veg) was a composite of two scoops each from seven garden beds. The other (labeled Fruit) was a composite of several scoops taken down the length of a newly-dug 6×30 foot bed that will be home to some berries and other small fruiting plants.

The results came back, and they contained some surprises. Here is the information in table form:

Component	Veg — 7 garden beds	Fruit — one garden bed
pH	6.4	5.4
Phosphorus (P)	353 lbs/acre (very high)	104 lbs/acre (high)
Potassium (K)	171 lbs/acre (low)	39 lbs/acre (very low)
Magnesium	334 lbs/acre (very high)	79 lbs/acre (high)
Zinc	28.6 lbs/acre (very high)	22 lbs/acre (very high)
Calcium	2331 lbs/acre	496 lbs/acre
Soluble Salts	0.1 (low)	0.1 (low)
% Organic Matter	4.2	3.6
% Nitrogen	0.16	0.11

What this all means

Seeing the numbers for the two areas side-by-side makes the differences stand out, but I will go over the components measured, one by one, to explain how I am using the information.

pH

For both samples, pH was on the acid end of the spectrum. The pH of 6.4 for the Veg sample is excellent for most vegetables, and no additions of limestone were recommended for that set of garden beds. However, the pH for the Fruit sample, at 5.4, was too low, too acidic, for many fruits. Blueberries will be happy at 5.4, but not much else. The Fruit test results came with a recommendation to add limestone: 75 pounds per 1000 square feet, to bring that pH up a bit.

The surprise here is that I had used a simple, home pH test kit last spring on part of the vegetable garden area. The pH as measured with the kit was at least 7 (neutral) or possibly higher. The pH kit relies on color-matching, and it seemed to me that my sample could have been between the colors for seven and eight.

We did find, though, when digging the beds, a couple of the plastic tags that come with tomato plants, that tell which variety they are. This suggests that a previous owner also had a veggie garden in this area, and they probably added lime to bring up the pH. Last spring, the soil sample for measuring the pH was from just a couple of beds, because it took awhile to get them all dug. It is possible that the new sample, a composite from seven beds, includes a mix of high and low pH areas.

I will need to check the pH of each of the seven planting beds to figure out which have a higher pH and which have a lower pH. Some may need a little limestone to improve the pH.

Phosphorus

Just wow. Neither of my planting areas needs any more phosphorus, possibly for years. These came back High (Fruit) and Very High (Veg). It may seem as though having high nutrient levels would be a good thing, but high levels of phosphorus can interfere with a plant’s ability to take up micronutrients, like zinc, that it may also need for good growth and productivity. The Texas A&M article Phosphorus — Too much and plants may suffer indicates that phosphorus levels above 150 ppm may harm plant growth, and levels above 350 ppm can kill some plants. It may be a miracle that my garden has been able to support any crops at all!

The high phosphorus levels mean that I should avoid composts that include manures, especially chicken manure, since those can add extra phosphorus to the soil.

My fertilizers also need to be low on phosphorus. Most fertilizers are labeled with the percentages of nitrogen, phosphorus, and potassium they contain. These are listed in that order, as N-P-K (nitrogen-phosphorus-potassium). That middle number, for my garden, needs to be as low as possible. The good news here is that one fertilizer that I keep on hand is a fish fertilizer labeled 5-1-1. This product offers plenty of nitrogen with a low amount of phosphorus.

Potassium

Measurements for potassium (K) came back low for both areas.

My 2018 article about potassium sources for organic gardens describes pros and cons of several potassium sources. In addition, my Garden Planner and Notebook contains, on page 12, a list of some commonly available organic fertilizer ingredients and what nutrients each one provides. Looking down the list, I can see that greensand is the one I will want to use.

Wood ashes add potassium but also can raise the soil pH. Since the “soil” here generally seems to have a low pH, that is not a drawback. The issue is more one of finding the wood ashes. Kelp meal would be a possible source to try, except that it can also add phosphorus, which I need to avoid. And, sul-po-mag brings magnesium with it, which the garden also seems to have in abundance.

Magnesium

Measurements for magnesium content for both planting areas came back as high (Fruit) and very high (Veg). No magnesium is needed, apparently, even though epsom salts (a magnesium source) did seem to help last year. I wonder whether the super-high levels of phosphorus made it harder for plants to use the magnesium that was already in the soil

Alternatively, it is possible that the magnesium in the soil was tied up somehow, bonded in a way that made it less available to the plants. Also, if the soil pH is very low, plants are less able to take in nutrients they need, like magnesium, phosphorus, and potassium. So, low pH could have been a factor in some of the Veg beds. (Another reason to check soil pH in each of the seven beds…)

The limestone recommended to bring up the pH in the Fruit area also will add more magnesium to that space, since limestone contains both calcium and magnesium in abundance.

Zinc

Zinc measurements came back high in both planting areas. If all the yards around here are high in zinc, that might explain the success of pecan trees locally. Pecans are big users of zinc. Many yards here have at least one pecan tree, and we saw lots of pecans in the fall. In north Georgia, pecan trees often need supplementation with zinc in order to make good crops, since zinc is less abundant in the soil up there.

Calcium

Calcium level in the Veg sample was a lot higher than the level in the Fruit soil sample, but a value-judgement of whether the levels were low-medium-high-or-very high was not given. A Mississippi State University Extension article includes this bit of information about calcium availability in soils that have low pH, such as in the Fruit sample:

Soils with favorable pH levels are normally not deficient in calcium. Acid soils with calcium contents of 500 pounds per acre or less are deficient for legumes, especially peanuts, alfalfa, clovers, and soybeans. At this level, limited root system crops such as tomatoes, peppers, and cucurbite would also need additional calcium. Soluble calcium is available as the Ca2+ ion and is needed for peanuts at pegging time and for peppers and tomatoes to prevent blossom end rot.
Secondary Plant Nutrients: Calcium, Magnesium and Sulfur ; publication number IS1039, by Larry Oldham, phd, 2019

For my garden areas, this means, again, that checking soil pH for each of the seven beds in the Veg area will be a good thing to do, in case any of these show a super-low pH. Maybe low calcium explains the wimpiness of last year’s green bean plants!

It also provides more support to add the recommended limestone to the Fruit area to improve plant health.

Soluble salts

The low measurements for soluble salts were another big surprise. Here we are, just five blocks from the beach, and the soluble salts are low! I will count this as a blessing. Many garden crops are less productive when soluble salts are high.

Organic matter and percent nitrogen

These measurements are just to provide a little more information about this new (to me) soil. The percentages of organic matter are better than I had expected. At 4.2 and 3.6, I may have to stop calling my yard a sand dune and refer to it instead as a sandy loam.

When working in the garden, it just seems like a lot of sand, but my past 30 years of working in north Georgia’s red clay may be coloring my judgement here. However, in that clay soil, I would want a higher percentage of organic matter, to help break up the clay and improve how it both holds and drains water.

To work on these numbers, to boost them slightly higher, I will need to rely more on cover crops than on composts and manures (because of that phosphorus problem…).

Fertilizers for the year, based on the soil test results

The soil test reports recommended additions of 34-0-0 fertilizer, for the nitrogen, and muriate of potash (0-0-60) for the potassium. These are both conventional fertilizers that are in the form of soluble salts. Muriate of potash is, essentially, potassium chloride. (You may recall from a long-ago science class that table salt is sodium chloride.) These salts dissolve readily in water and are instantly available to plants as soon as they are watered in to the garden.

However, I am an organic gardener. Soluble salts are not part of my game plan. Hence, the decision to use greensand as a potassium source. In addition, I will be adding some Azomite (not listed in the Garden Planner and Notebook), another kind of pulverized rocks, as a source of additional micronutrients and a tiny bit more potassium.

My nitrogen source, selected by looking at page 12 of my Garden Planner and Notebook, could be either feather meal or alfalfa meal. Feather meal smells a lot like dead things, but the odor only lingers for a few days. No local stores carry feather meal, though, which leaves me (thankfully) with the better-smelling alfalfa meal.

I plan to follow Kevin Meehan’s instructions for DIY alfalfa fertilizer, posted on Rodale Institute’s website, which uses alfalfa pellets that can be found at any local feed store. This should be — yet another — interesting adventure, along with the other “special projects” I have listed in my Garden Planner for the year. Wish me luck?

Can I Grow Food Organically on a Sand Dune?

31 December, 2020 by amygwh

This past summer, I was told by a farmer at a local farmer’s market that growing food organically is impossible here on the Mississippi Gulf Coast. However, I have found that to be not precisely true.

What is true is that my organically-managed garden is supplying a small but steady flow of veggies to the kitchen. What is also true is that a lot of those veggies have been eggplants and okra. As long as I love eggplants and okra, my summer veggie garden will be a smashing success. Ditto for radishes in the spring and fall.

Gulf coast early fall harvest of okra, peppers, greens, and one winter radish.

Unlike market farmers, home gardeners like me have the benefit of not needing to compete with the produce section of the local supermarket. We don’t expect our gardens to supply all the standard veggies the whole year round. This means we can focus our efforts on crops that don’t need chemical interventions to produce food in our yards.

It can also help if a gardener is a bit flexible in how to measure success in the garden.

Part of the path to success is identifying which exact crops will produce well in our gardens, then growing and appreciating those crops. Another part of the path is to keep in mind the part of the Serenity Prayer that reminds us to not get too fussed about the “things I cannot change” and focusing instead on knowing which things can be changed and which can’t.

My sand-dune-based garden

This Gulf Coast sand dune, 28 feet above sea level in plant hardiness zone 9a, is very different from the location of my previous 30 years of gardening in the red clay of the Georgia Piedmont region in hardiness zone 7b. In the “things that cannot be changed” category, the soil here is, as mentioned already, mostly sand. I can pile compost on top of it, but I cannot change the basic sandiness of the yard. I also cannot add more cold to our winters, which means some plants that need a lot of cold, like Rhubarb and many varieties of apples, will not thrive here. The flip side of that is that now I can grow some sub-tropical fruits.

Radishes pulled from the garden, with leaves still attached. Some radishes are round and red, some round and purple, some long and red. — November radishes, three kinds.

Many crops are more adaptable than Rhubarb and cold-loving fruits, especially the annuals that I usually grow in the garden. In our move from Georgia last spring, I brought seed packets for some of those crops left over from the past couple of years. Some of those crop varieties have worked well, and some haven’t.

I’ve already noted that eggplants, okra, and radishes have been wildly productive here. However, a whole lot of crops have been less happy here on my sand dune.

A sadness of beans

Bean crops, which always totally rocked the garden in north Georgia, have not done well here. The first planting gave us a few handfuls of beans, not the usual superabundance, before they died, and I was puzzled, but planted more. When the next planting died, I had to start thinking harder about what could be wrong. English peas planted in early fall met the same fate as the second sad planting of beans. They just faded away.

I can see a few possible reasons for the problem. One is a lack of some essential nutrient, and another is a high soluble salt content in the soil. Until I can deliver a soil sample to the state testing lab, those are both just guesses.

A third possible reason is the relatively high pH of my sandy soil, which is way above 7. Beans tend to prefer a lower pH. This year, as I prepare the planting beds, I will be digging in some sulfur to start bringing that down (sulfur can take years to have any effect). In addition, I hope to hunt up some gypsum to use for a calcium source, since that can also help alleviate the high pH — and it might help with the soluble salts, too.

There is a good chance that I can change the soil pH a little bit, and I can amend the soil to bring in missing nutrients. I might not be able to do much about soluble salts, since my garden is only five blocks from the beach. Salt is in the air! If salts are the problem, beans may never do well here. It will be interesting to find out.

Every crop turns a bit yellow as it grows

As my summer crops grew this year, I saw that they all became less richly green over time. Back in north Georgia, a little bit of Epsom salts (an affiliate link to the product), a source of soluble magnesium, would fix that when extra nitrogen (like in a fish-based fertilizer — see article at this link) didn’t seem to help.

I discovered that Epsom salts works here, too, but they need to be applied much more frequently. The sandy “soil” lets dissolved nutrients, like the magnesium in Epsom salts, wash away, down out of the root zone, very quickly. Clay soils, like those in north Georgia, hold on to nutrients much more tightly, keeping them up in the root zone longer.

This summer, I ended up needing to apply a weak solution of Epsom salts (two rounded tablespoons dissolved in two gallons of water, then applied as evenly as I could manage over two 3×12 foot beds) every couple of weeks to keep the plants looking healthy. For my fall crops, this schedule stretched out to 3-to-4 weeks.

One item on my “to purchase” list this spring is a big bag of a crushed-rock-magnesium source that will not wash down through the sand so quickly. Big, gravel-sized chunks are my preference, but more finely pulverized products are easier to find. I am considering Sul-Po-Mag and Azomite (two affiliate links) as possible sources.

With some additional research into sources and work in applying what I’ve found to the garden, there is a good chance that I can fix the low-magnesium problem.

Other crops that grew less well than preferred

My corn patch was a bust. We ended up with a few patchy ears of sweet corn, which was a disappointment. I think the cause was a mineral-nutrient deficiency problem. I plan to try again this coming year after amending the soil more intensively (I had added a lot of purchased compost this past spring.)

Zucchini squash was very productive for a very short time, then was killed off by squash vine borers. The winter squash did not do well at all. I had planted a butternut, which can withstand the borers, but the squashes that the plants produced were tiny. Then, the leaves all got mildewed and the plants died. For winter squashes, I will — again — keep working to improve the soil with composts and mineral amendments and also try some different varieties. I know that ‘Seminole’ pumpkin squash should do well here, but I am hoping for something thicker-fleshed, sweeter, and with a shell that won’t require a sledgehammer to break through (I have grown it before…).

Sweet potatoes were not nearly as productive as I would have preferred. The good news is that I did dig up about 20 pounds of sweets from the garden. My experience in north Georgia, though, shows me that a much larger harvest is possible from the number of plants grown. From similar space and number of plants in Georgia, the harvest was typically twice that amount.

Tomatoes from the fall plants, brought inside in late November.

Tomatoes in the spring were not very productive. A couple of plants just plain died (drowned, when the garden flooded) and the rest quit making fruit in mid-summer. Apparently, that is a normal occurrence here, caused by nighttime high temperatures. The late-summer tomatoes that I grew were only just beginning to ripen before our first frost on the last night of November.

These tomato issues can be fixed (I hope) with changes in the timing of my plantings. Luckily, this year I am already here, and the garden beds are dug, so I should be able to get tomato plants into the ground well before April. (Our last frost should be around the end of February.) Last year, I was just starting to prepare the garden beds in April, because we moved here at the end of March.

Beets have been a bust. I planted one set of seeds in the late summer, and they came up, but then the little plants faded away. A second planting produced more little plants, and most of them are still present, but they have not grown much.

Stink bugs! Caterpillars!

In addition to soil problems, there were some pests. This is not really a surprise, since tiny plant-eaters are everywhere. My two largest categories of pests were stink bugs and their relatives, and caterpillars of several species.

Immature leaf-footed bugs, the nymph stage, on Southern peas.

Stink bugs and leaf-footed bugs damaged tomatoes, peppers, and the Southern peas. Most evenings beginning in early summer, I spent a few minutes out in the garden with a large plastic cup of soapy water, hunting for these pests. A whole platoon of immature leaf-footed bugs could be dislodged into “the cup of doom”, where they would drown, with one shake of the bean, leaf, tomato, or pepper on which they were gathered.

Caterpillars plagued the garden until late summer. Every leafy green vegetable that is normally recommended for the summer garden was attacked, in addition to tomatoes and peppers. Weirdly, though, the caterpillars that I expected to see on cabbage-family plants in fall never appeared. My kale, collards, and arugula have been unmolested. I count this as a blessing.

Fire ants

Fire ant mounds were all over the yard when we moved in. It took awhile for me to get around to dealing with them, but I did find that the Texas A&M recipe, noted in my second article on fire ants, that uses Medina Orange Oil (affiliate link) and Blue Dawn dish soap works great here. Smaller mounds were destroyed with one treatment. Larger mounds took two or three tries. As new colonies have moved in, I have continued using the DIY recipe. This recipe is not strictly organic, considering the range of ingredients in the Blue Dawn dish soap. When my giant bottle of Blue Dawn is finally empty, I plan to try using liquid castile soap, which does not include the petrochemical ingredients, as a replacement for the dish soap.

Before I started seriously hunting down and destroying the fire ant colonies, the ants were eating okra in the garden. It was a surprise that the ants on the okra really were fire ants, not like the kind of ants back in Georgia that farmed aphids on the okra. Figuring this out was painful. Welts from fire ant bites/stings take a long time to heal.

Some happier crops

Plenty of crops have done pretty well in my sand dune garden. Here are some happy pictures of examples:

The plan for now

One great feature of this garden is that digging holes and creating new planting beds is much easier than in the clay in north Georgia. Even better, wet sand never sticks to the shovel in huge messy globs like the red clay can. However, the big drawback is that the sand doesn’t hold onto much of anything. Water and nutrients — like from fertilizers — wash right through.

To improve this situation, I will keep adding composts — my own compost pile is far enough along to reduce the amount I need to buy this year. In addition, I will be buying those crushed rock sources of nutrients, to improve the health and productivity of my crops, as noted above. These additions should make organic gardening in the sand more successful.

In future posts (I promise, they will be more frequent in the coming year), there will be more information about the actual plants in the garden.

I hope that your gardening has provided good food through 2020, and that the coming year brings more garden adventures and successes! Keep well.

Growing (and Eating) What’s Good for the Garden

7 April, 2019 by amygwh

New gardeners often are advised to grow foods that they and their families like to eat. It makes sense. Why grow tomatoes if no one at home will eat them? That advice, though, is less firm for gardeners who have been working their soil for a few years. Longer-term gardeners should consider branching out a bit, with regard to what they grow. Here is why:

Different crops can improve your crop rotations

Crop rotation is the practice of growing different kinds of crops in succession within a growing space. “Different kinds” here means plants from different plant families. An example of crop rotation, to illustrate the practice from one space in my garden, is this: kale (fall/winter), followed by peppers (summer), followed by garlic (fall/winter).

Why should you be concerned about your crop rotations?

Bowl filled with shelled cowpeas surrounded by garden vegetables including okra, tomatoes, and peppers. — Cowpeas, in the bean family, help diversify my crops in summer.

University of North Carolina’s article, Advantages of Crop Rotation, explains that rotating crops can reduce buildup of pests and diseases. It can also improve the balance of nutrients in the soil and improve soil structure.

Organic gardeners, especially, who may see themselves as stewards of the soil, will find that crop rotation is a practice that can enhance their gardens.

A chef argues for eating more kinds of crops

I remember reading a Yale Environment 360 interview with chef Dan Barber who explained how he came to understand that supporting sustainable agriculture can mean learning to eat new crops.

The central example discussed in the interview was a farm that was growing emmer wheat, an ancient variety that Barber was excited about using in recipes. This is the relevant bit in the interview:

…I was standing in the middle of a field, and all of a sudden discovered that he [the farmer] was growing very little wheat, and that instead he was growing a whole suite of lowly grains like millet and buckwheat and barley, and leguminous crops like Austrian winter peas and kidney beans. He was growing a lot of cover crops like vetch and clover. And they were all meticulously timed and spread out among the 2,000 acres I was standing in the middle of. And that’s when I sort of had this agricultural epiphany. But it led to this gastronomic epiphany, which was that here I was as a farm-to-table chef waving the flag of sustainability and realizing that I wasn’t supporting most of the farm. In the case of Klass [the farmer growing the emmer wheat], he needed these lowly crops and cover crops and leguminous crops because his soil health needed it to grow wheat. You couldn’t get the wheat unless you grew all these other crops. And you had to time it in this way that brought the fertility to the soil to give you this incredible tasting wheat.
Diane Toomey, How to Make Farm-to-Table a Truly Sustainable Movement, interview with chef Dan Barber, Yale Environment 360, 15 Sept. 2014

Most of us are not going to develop elaborate rotations for the production of emmer wheat, but the interview made me feel like less of a loon for growing – and learning to prepare and eat – crops that are not my favorites, all because I thought they’d be good for the garden.

Adding more plant families to the rotation, for home gardens

An example of adding beets

Red beet with red-veined green leaves growing in soil. — Garden beet in April.

Years ago, I decided to expand my spinach/amaranth family plantings by growing beets, even though I didn’t really like beets. I could have planted more spinach, instead, but the phosphorus level in my soil was a little high. I knew that a root crop like beets would use up some of that extra phosphorus, helping to rebalance the nutrients in my garden’s soil.

Over time, as a result of this decision, I learned how to prepare beets in a way that Joe and I actually like. Now, beets are just one more good food that we look forward to bringing in from the garden.

I have worked on collard greens in the same way, but with less success. The good news is that Joe likes them.

Why grow collard greens?

A good reason to grow collard greens is that collards (and mustards) help suppress the root-knot nematodes that are such a big problem in Southern soils. At the garden/farm where I used to volunteer, the winter mixed-greens crop of collards, mustards, kale, and radishes was called a “fumigant” crop for the good work it does in cleaning up the ever-present nematode pests in the soil.

These greens can stay in the ground all winter long in the South, harvested leaf by leaf, so they work on the soil for many months. Tilling in the remaining leaves and roots about a month before spring planting just frosts the cake of their beneficial effects.

Plant families for garden crops

The list of plant families that include food crops, to enhance your own garden crop rotations, is large. Here are examples of plant families and some crops in each one:

Tomato family – tomato, pepper, eggplant, potato, tomatillo
Cabbage family – cabbage, broccoli, kale, collards, mustards, radish, turnip, kohlrabi, Brussels sprouts, cauliflower, arugula/rocket
Bean family – bush beans, pole beans, Lima beans, peas, Southern peas, cover crops like clover and vetch
Onion family – onions, garlic, shallots, chives
Carrot family – carrots, parsley, cilantro, parsnips, dill, fennel
Spinach family – spinach, Swiss chard, amaranth, beets, Good King Henry
Squash family – cucumbers, summer squashes, zucchini, winter squashes, pumpkins, melons
Sunflower family – sunflowers, lettuce, chicory, radicchio, escarole, endive
Mallow family – okra, roselle
Morning glory family – sweet potatoes
Mint family – mint, basil, oregano, thyme, anise hyssop, rosemary, sage, marjoram
Borage family – borage
Grass family – corn, wheat, rice, oats, lemongrass
Buckwheat family – buckwheat, French sorrel (and rhubarb, which is not a plant for the South)

Growing some chicories

Pale green lettuces and dark red radicchio plants growing together in a garden bed. — Radicchio (right) is a kind of chicory, which is in the same plant family as lettuces (left). Growing them together makes crop rotation simpler.

Personally, I would like to see more gardeners branching out a bit into the unknown, in terms of crops. That is why I took seedling chicories to the Soil3 Garden Show, to give away with a handout of information about chicories.

I have found that these plants are relatively pest-free in our area. For organic gardeners in the South, pest-free crops are an amazing gift! Chicories also have deep roots, which can help break up heavy soils and can bring up nutrients from deeper soil layers.

Clump of 'Italiko rosso' chicory - upright leaves are dentate and have red veins. — ‘Italiko Rosso’ chicory in the fall, ready for harvest to use in salads or on pizza.

In addition, they are useful in the kitchen as greens, which we all probably need to eat more of (chop some up to put on your pizza), and the roots can be roasted to make a coffee substitute. If the plants stay in the garden over a winter, they will produce a tall stem with blue flowers, in spring or early summer, that will support many pollinators.

Not everyone will appreciate the bitter flavor of chicories, but if you like the flavor of radicchio in your salads, you may like other garden chicories, too. The very first one I grew, Italiko rosso (which Baker Creek labels as a dandelion, possibly because of its leaf shape), is still a favorite.

Hope your gardens are all growing well!

(If this blog post is interesting or useful to you, please “like” or “share” it. Thank you!)

Broccoli, Beets, and Boron – Updated

8 March, 2019 by amygwh

Soils in the region where I live are short on the mineral boron, an essential plant micronutrient. The University of Georgia soil lab doesn’t measure boron levels in its routine test for garden soil, but it does include a recommendation to add some to a home vegetable garden. This is the recommendation:

“Apply 1 tablespoon of borax per 100 feet of row to broccoli and root crops such as turnips and beets. This can be applied by mixing the borax thoroughly with approximately 1 quart of soil in a container and then applying the mixture along the row; or it can be mixed with a quart of water and applied to the soil in solution.”
University of Georgia, Soil Test Report, basic soil test for Home Vegetable Garden, 2018

What is a micronutrient?

The micronutrients are needed in tiny amounts, but they are essential for plant growth. Boron is one of several micronutrients that plants need. Other micronutrients include copper, iron, and nickel, among others.

For boron, the difference between not-enough and too-much is a pretty narrow range, according to K. Kelling at the University of Wisconsin and Ron Goldy at Michigan State Univ. Extension. This means that great care must be taken to not use too much.

How does boron help plants?

Golden beets growing in the garden - beets are a crop that need a little more boron than others. — Golden beets growing in the garden – beets are a crop that need a little more boron than others.

UMass Extension, Amherst, says that boron “is required for many different aspects of plant cell functioning, including protein synthesis, development of cell walls, carbohydrate metabolism and sugar transport, pollen growth, fruit set, and seed production.”

Sounds important, to me!

What happens when plants don’t get enough boron?

The UMass information about boron deficiency lists these possible effects of too-little boron:

“stunting and distortion of the growing tip”
“brittle foliage and yellowing of lower leaf tips”
reduced flowering
reduced fruiting
distorted fruit
“brown heart” (mushy brown centers) in root crops like turnips and rutabagas
hollow stems in broccoli and cauliflower
brown or otherwise discolored curds on cauliflower

Kelling’s Soil and Applied Boron publication adds that cabbages that are low on boron may show an “internal breakdown of head”.

Which plants need the most boron?

Some vegetable crops need more boron than others.

Broccoli growing in the organic home garden.

Ron Goldy’s U Michigan publication lists crops and their relative need for boron. The high-need vegetables for boron he includes are these:

broccoli
cauliflower
celery
table beets
turnips

How can I provide boron to my garden?

One way to add boron is to follow the instructions on the UGA soil test report, to mix a tablespoon of borax in water or with soil and to spread that across a 100-foot row of garden, especially in areas where higher-need vegetables are growing. If your garden is not in rows, or is smaller, it will need less borax.

The borax you will need is in the laundry section of your grocery store, in the box of 20 Mule Team Borax. This should be fine for organic gardens, because it is a mined mineral.

You will need to be careful with this product, though, because it is easy to use too much. Do not apply the boron every year without having the boron levels tested at a reliable soil lab.

If you prefer to use another product, one that contains many micronutrients, including boron, to safely fill any gaps, try kelp meal. It is much more difficult to use too much boron when using kelp meal, because it is a much less concentrated source of the micronutrient. There is enough, though, to help your plants. Just follow package directions for safe use in your organic home garden.

Georgia isn’t the only state with low-boron soils

The 20 Mule Team Borax company notes that boron will be at low levels in soils that are sandy, or acidic, or that are low in organic matter (like Georgia clay!), or that are in areas of high humidity.

The company has found that low-boron levels are a common problem in soils east of the Rockies and in the Pacific Northwest. The middle of the country and the Southwestern region mostly have sufficient boron.

To learn more about soil fertility in organic home gardens, read my posts about potassium sources, soil pH, building good garden soil, and side-dressing your garden crops.

Good Garden Soil

4 January, 2019 by amygwh

Small farm with red clay soil in north Georgia produces a lot of good food.

Several gardening books I’ve read include the note that good garden soil is a sandy loam, rich in organic matter. My yard’s soil is naturally a massive gob of red clay — like in the nearby photo — not at all what is recommended.

Red clay is actually not all bad. It holds nutrients much better than sandy soil, so it doesn’t need as much fertilizer. It also holds water — sometimes too well! — which means it is slow to dry out. When it does get dry, it becomes brick-hard and tough to dig.

Plants benefit from the nutrient-holding and water-holding capacity of clay soil. The problem is that the clay compacts and does not allow roots to move easily through the soil, and it doesn’t have good air spaces (which roots need).

Not every yard in this area has such dense red clay as mine. When we first moved here (in 1990), and for years afterward, an older gentleman in Kennesaw grew roses, lots and lots of roses, out near the road on Cherokee Street.

I stopped to talk with him once, when I saw him out tending his roses. He said that a friend brought him a truckload of oak leaves to use for mulch each year, but that his yard had naturally good soil. That comment stunned me into speechlessness for a moment — my experience was so different!

Most people I talk to around here have soil like mine. This may be why so many new gardeners use raised beds filled with soil mixes that don’t include clay.

My gardens, though, are not in raised beds. They are in the ground, in that red clay. I add amendments like compost (from my yard) and soil conditioner (from a garden center) to increase the organic matter and microbial activity. The amendments make the clay soil a more welcoming place for the roots of my crops.

How to create good garden soil from red clay

A recommendation from Cooperative Extension’s “Ask an Expert” page for improving clay soil, is below. The picture of the compost bin nearby, though, is a clue about at least one important amendment.

Here is the Extension Expert’s recommendation:

Choose an organic soil amendment like composted yard waste, rotten leaves, or well-rotted manure (make sure any composted manure does not contain residual herbicides!). Material that is well-rotted will not smell unpleasant; it will smell like the earth.
Spread a 3 to 4 inch layer of your chosen amendment on top of the clay soil; work it down into the soil about 6 to 8 inches.
After the compost has been worked into the soil, you can spread an inch or two layer of sand on top and gently spade it in.
Before planting in spring, lay on another 2-3 inch layer of compost and work it into the soil, about 6 to 8 inches down (the depth of a shovel blade).

Walter Reeves, The Georgia Gardener, has an updated article on Soil – Bed Preparation that suggests bagged soil conditioner as an alternate for compost. His article also suggests adding Permatil to the mix, to keep the clay soil looser, as the composts and soil conditioner decompose and disappear.

Permatil is expanded shale, and it creates air spaces in the soil. I have added a similar product to part of my upper garden, an area I don’t re-amend as often as the veggie area because it has some perennials (permanent plants).

If you can’t find Permatil but are interested in trying something similar, look for Espoma’s Soil Perfecter, bits of kiln-fired “ceramic mineral” that works in a similar way to open up air spaces in the soil.

Nutrients and pH?

The Extension recommendation above does not address soil pH (acid level) or fertility/nutrients. The Expert who answered the question may have assumed that everyone will know to send a soil sample to their state’s soil lab (Georgia’s is at UGA, in Athens) through their local Cooperative Extension office.

If you are not sending a soil sample to your state’s soil lab, consider buying a pH test kit (see my article on Soil pH and Garden Success for more information). For fertility, if you don’t have a soil lab recommendation for fertilizer, choose an organic-approved garden fertilizer and follow the package directions. To learn more about nutrient sources for your garden, check out my articles on Potassium Sources for an Organic Garden and on Fish Emulsion Fertilizers.

Dig soil when ground is not soggy

You will know your clay soil is dry enough for digging when you can squeeze a handful of it and it breaks up into bits. You should not be able to roll it into the kind of snake-shapes that can be coiled to make pottery bowls.

Clay soil needs to be not-soggy at digging time, partly so you can get the clay to let go of your shovel and partly so it won’t reform into giant, brick-like clods when the lumps finally dry. Digging in wet clay soil also causes it to compact, making it lose the air spaces that are vital to healthy plant roots.

Winter is a great time to work on improving garden soil or to create new planting beds. Here in the South, we have some pleasantly cool afternoons mixed in with the cold ones, which means we have good opportunities for working outdoors.

Right now, though, the ground is squishy under my feet when I walk in the yard. I just need to wait for the rain to stop and the ground to get drier.

Soil pH and Garden Success

15 December, 2018 by amygwh

When a garden hasn’t been doing well, one of the first conditions to check is the soil’s pH, its acid-alkaline balance. The pH scale goes from 0 to 14; 7 is the neutral pH, measurements below 7 are acidic, and measurements above 7 are alkaline.

For reference, distilled salad vinegar has a pH in the range of 2 to 2.5 (acidic), and cold-process soap has a pH in the range of 9 to 10 (alkaline).

Soil pH influences how well plants can take in nutrients from the soil, so getting a garden’s soil into the best pH range for your plants will help them be healthier and more productive.

What is less well-known is that correcting a pH that is either too high or too low takes time. Testing soil pH should be done now, or soon, for gardens that have not done well in the past year.

What pH is good for gardens?

Blueberries will be ripe beginning in mid-to-late June. — Blueberry plants prefer a soil pH near 5.

Most garden veggies need a soil pH of between 6 and 7. Where I live, northwest of Atlanta, the natural soil pH is lower than that range — it is naturally acidic. With that acidity in mind, many people here routinely add lime to their lawns and gardens without checking the soil pH first, and end up with a soil pH that is too high.

When I worked at the local Extension office and managed the soil samples that went to the soil lab at University of Georgia (UGA), it was not unusual to see some samples with soil pH around 5, but others with pH higher than 8. Those higher pH soil samples were from lawns and gardens that had been limed pretty much every year.

Once, a friend who decided to plant blueberries in the space where she had originally kept a vegetable garden sent a soil sample in to the lab at UGA. The lab found that the pH of her soil was 7. This pH level was not a surprise because she had been spreading ashes from her fireplace on the garden. Wood ashes are a good source of potassium, but they raise the soil pH.

For many veggies, a soil pH of 7 is fine, but the blueberries she hoped to plant in that space prefer a pH closer to 5. That soil needed some work before it would make a good home for blueberries.

How can I find the pH of my garden soil?

Example of easy to use soil pH test kit for home gardeners.

The most reliable method of finding your garden’s soil pH is to send a soil sample to your state’s soil lab. Call your local county Cooperative Extension office to find out how to take a representative soil sample, how to package it, and the lab fee for this service.

Another option is to purchase a pH test kit at a local garden center. One I have used (pictured nearby) includes a container with color chart for comparison, capsules of pH-indicator-powder to add to the container, and instructions.

The basic instructions for this kit, and others:

put a tiny bit of garden soil into the container
add the indicator powder
add water up to a line near the top
put the lid back on the container, then
mix the parts together by shaking the container until color develops.

You find the pH by comparing the color of your sample to the chart on the front of the container.

Soil sample in pH test kit with water and indicator powder, to read the soil pH. — Sample in pH test kit shows pH of soil in my upper flower bed to be about 6.5.

How to lower a too-high soil pH

The UGA soil lab sent information to my friend about how much aluminum sulfate (the cheapest option) to add in order to bring the pH down to a better level for blueberries. If you know that the pH of your garden soil is too high, but don’t have a lab-recommendation for how to lower it, the amount of elemental sulfur (my preferred option) needed can also be found in a table by Clemson University Extension, in its Changing the pH of your soil publication.

For a soil pH that is only slightly high (about 0.5 higher than the desired level for your plants), one of my county’s former Extension agents used to recommend mixing sphagnum peat into the soil as a quick fix. Iowa State University Extension suggests other amendments that can lower a too-high pH, including “elemental sulfur, aluminum sulfate, iron sulfate, acidifying nitrogen, and organic mulches.”

There is a note, too, that a very high pH (over 8) is hard to bring down. When the local Plant-a-Row-for-the-Hungry garden (one of my volunteer groups/projects) was at a location that had a high-pH soil, we added the recommended amount of sulfur several years in a row before the pH started to come down.

How to raise a too-low soil pH

The Iowa State University publication How to change your soil’s pH includes a table showing how much ground limestone will be needed to raise soil pH. If you have hydrated lime handy, and think it might be a “quicker fix” for a too-low pH, please don’t try it. The risk of raising the pH too high with this product, by accident, is large. Lowering the pH after over-liming is difficult and can take a long time. Use ground limestone instead of quick lime or hydrated lime.

It takes more lime to raise pH in a clay soil than in a sandy soil. In general, according to the table in the Iowa State publication, for 100 square feet of clay-soil garden, it takes 5 to 6 pounds of limestone mixed into the top six inches of soil to raise the pH by 0.5.

When is the best time to adjust the soil pH?

For my friend’s blueberries, the UGA lab report recommended that the bushes shouldn’t be planted until 6 months after applying the sulfur. If she added the sulfur in October, that means blueberry-planting should — for best effect — wait until April. That is pushing the boundary for good planting time for woody plants like blueberries; as spring progresses and the weather warms, newly planted bushes are less likely to do well. They need time in the soil for their root systems to become established before being stressed by the heat of a Georgia summer.

What this means is that soil testing should be done now, if it hasn’t already been done, so adjustments to pH can be made soon enough to benefit plants that will be planted in spring.

What soil pH is best for my plants?

An article by Lewis Hill, published in Robert Rodale’s The Best Gardening Ideas I Know (1983) includes a list of some garden plants and the pH ranges they prefer. I’ve pulled some of the food plants from his list to post here:

pH 4 to 5: blueberry
pH 5 to 5.75: blackberry, grape, parsnip, plum, potato, pumpkin
pH 5.75 to 6.5: bean, citrus fruits, cowpeas, currants, gooseberry, oats, pepper, rutabaga, rye, squash, strawberry, tomato, turnip
pH 6.5 to 7: apple, beet, broccoli, buckwheat, butternut, chicory, chives, cucumber, eggplant, endive, kale, leek, muskmelon, onion, pea, peach, radish, raspberry, rhubarb, spinach, watermelon, wheat
pH 7 to 7.5: alfalfa, asparagus, barley, cabbage, carrot, cauliflower, celery, lettuce, nasturtium, parsley

This list may help other gardeners in planning what to plant where, but it is comforting to remember that plants will still grow and produce in soil that is slightly outside their preferred pH range.

This is lucky, since most of us grow many of these plants mixed all together in our gardens. However, for peak production, planting in soil that is actually the preferred pH for each crop works best.

Succession planting with preferred pH for each crop in mind

When I plant Irish-type potatoes in the spring, I will have added some sphagnum peat to their soil to bring the pH down a bit, but not all the way down to 5. Knowing the pH preferences of other crops helps me know what to plant after the potatoes in that space. For example, cabbages in that space would likely be a total bust, because their pH preference is so much higher (7 to 7.5!).

After potatoes are harvested, a better option than cabbages would be to let a nearby vining crop, like melons, sprawl across that space. Another option would be to plant a crop there that prefers a lower pH range, like beans or cowpeas that thrive at pH 5.75-6.5.

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