How to alkalize soil?

20 Aug Soil Composition in Phoenix, Arizona

The soil in Phoenix is some of the poorest in the country, heavily compacted and alkaline, full of salts and rocks. To garden in this soil requires generous additions of organic matter, preferably well-matured compost. Break up the first 12″ of the soil and remove any large rocks. Mix in the compost, along with gypsum to combat the alkaline Ph. Plan on repeating this process every time you plant a new crop. Other vegetable garden ideas include raised gardening – highly recommended – and container gardening. Raised beds retain moisture, but at the same time they allow excessive moisture from monsoon rains to drain very quickly.

If you’ve asked yourself this question, we can help. Should You Feed Your Plants Or Feed Your Soil?

Vegetables as Ornamentals

Container gardens can be a rewarding way of gardening for beginners. They provide a colorful focal point, accent your home’s architecture, and can be moved around for easy accessibility. Choose large containers with a capacity of five gallons or more and fill with an organic soil mix. Place the containers in a protected area, sheltered from the wind and frost. Containers dry out quickly, so be prepared to water often.

For more information about our All Natural N’Rich Soil Enriching Conditioner, !

Try planting an Italian garden with a tomato, basil as a filler, and oregano to cascade down the pot. Mix colorful lettuces with edible nasturtiums for a cheerful salad garden. Cucumbers, dwarf forms of pumpkins and winter squash, and sugar snaps can easily be trained to grow vertically in containers, leaving room to fill in with colorful annual flowers.

Soil Alkalinity


Soil alkalinity or salinity is a condition that results from the accumulation of soluble salts in soil. Most of the alkaline soils are found in the desert environments throughout the world. Although saline soils do occur in humid regions in areas affected by sea water, the most extensive occurrences are in arid regions, where they usually are found in low-lying areas where evaporation concentrates the salts received from more elevated locations in surface water, ground water, or irrigation water. Since low-lying areas are most easily cultivated and irrigated, they have the greatest agricultural value. The problems connected with soil salinity in these low-lying areas are of major importance in highly developed agriculture in desert regions. The degree of alkalinity of a soil is conveniently expressed in terms of pH values. The pH scale is divided into 14 divisions or pH units numbered from 1 to 14. Soils with a pH of 7 are neutral. Soils with pH values below 7 are acid or “sour” and soils with pH values above 7 are alkaline or “sweet”. A pH of 9 is ten times more alkaline than a pH of 8 and a pH of 10 is ten times more alkaline than a pH of 9. Thus, a soil with a pH of 10 is 100 times more alkaline than a soil with a pH of 8 (Black 1957; National Plant Food Institute 1962).

Get a lawn your neighbor will be jealous of

Spring in Arizona is a magical time when the desert comes to life in all its splendor.

You can encourage that splendor in your own yard while keeping in mind the state’s unique climate and plant life. Doing so will make your flora pop and draw the eye of your entire neighborhood.

Use these seven tips to make your lawn and garden something your neighbors will be jealous of this spring.

Weed often

One of the easiest and most effective ways to ensure your lawn and garden remain a showcase is to continually weed because, once they start cropping up, they seem to never end.

The best way to keep on top of weeds is to stop them from multiplying while they are seeds. Do so by regularly spreading lawn and garden weed preventers. Because weeds germinate at different times, keep applying to deal with each new crop before it pops up.

Additionally, mulch your yard to block the light that weeds need to grow.

Turn compost

Compost will make your garden thrive, as it enriches soil, helps keep moisture, suppresses plant diseases and pests, and reduces the need for chemical fertilizers, according to the Environmental Protection Agency.

Turn your compost every few weeks to let in air and encourage the organic reactions that allow it to thrive.

Fertilize and mulch

Fertilizing helps plants to thrive, so you’ll have beautiful flowers and delicious produce throughout the season. The right fertilizer, such as Ferti-Lome from Ace Hardware, comes in a variety of options, so you can meet all your garden’s needs as the season progresses.

After composting and fertilizing, mulching will give a protective top layer to your yard. In addition to suppressing weeds and preventing them from germinating, mulch helps retain moisture and insulate soil. Pay particular attention to the areas around tree and shrub roots.

Test soil

A commonly overlooked way to boost the vibrancy of your garden is to regularly test and fix your soil’s pH levels, with a kit you can pick up from your local garden store.

The ideal pH level is 6.5, according to Organic Lifestyle Magazine, with 7 being neutral, above 7 being alkaline, and below 7 being acidic. Slightly acidic soil will effectively break down nutrients, making for a fertile growing environment.

You can raise soil pH by adding limestone and lower it by adding sulfur. Test and adjust every few weeks.

Prune flowering shrubs

Pruning shrubs after they bloom maximizes their beauty and allows them to bloom in full.

Prune once a year to maintain the shrubs’ shapes and to rejuvenate their blooming potential, according to The Spruce. If you prune early in Spring, you may not see blossoms, but your shrubs will be healthier in the long run.

Plant perennials

In Arizona’s hot, arid climates, perennials are popular because they live for several years, as opposed to annuals. If you want a lovely garden throughout the year, look for perennials that bloom at different times, so you’ll always have pops of color.

Just as with other plants, perennials need to be fed, watered and cared for to ensure they return year after year.

Tend fruit trees

Fruit trees are both lovely and a source of delicious and healthy treats.

Start the season by culling dead branches. As you begin to see growth, prune the trees, so the fruit is four to five inches apart. This encourages fruit to mature to full-size and will yield a healthy crop.

No matter your tasks in the yard this spring, visit Ace Hardware for expert help and all the products you’ll need to make your lawn and garden the star of your neighborhood.

What Makes Soil Alkaline – Plants And Tips For Fixing Alkaline Soil

Just like the human body can be alkaline or acidic, so can soil. The pH of soil is a measurement of its alkalinity or acidity and ranges from 0 to 14 with 7 being neutral. Before you begin growing anything, it is good to know where your soil stands on the scale. Most people are familiar with acidic soil, but exactly what is alkaline soil? Keep reading for information on what makes soil alkaline.

What is Alkaline Soil?

Alkaline soil is referred to by some gardeners as “sweet soil.” The pH level of alkaline soil is above 7, and it usually contains a great deal of sodium, calcium and magnesium. Because alkaline soil is less soluble than acidic or neutral soil, availability of nutrients is often limited. Because of this, stunted growth and nutrient deficiency are common.

What Makes Soil Alkaline?

In arid or desert areas where rainfall is slim and places where there are dense forests, soil tends to be more alkaline. Soil can also become more alkaline if it is watered with hard water that contains lime.

Fixing Alkaline Soil

One of the best ways to increase acidity in soil is to add sulfur. Adding 1 to 3 ounces of ground rock sulfur per 1 square yard of soil will lower pH levels. If the soil is sandy or has a lot of clay, less should be used, and it needs to be mixed in very well before using.

You can also add organic matter such as peat moss, composted wood chips and sawdust to bring down the pH. Allow the material to settle for a couple of weeks before retesting.

Some people prefer to use raised beds where they can control the soil pH easily. When you use raised beds, it is still a good idea to get a home soil test kit so that you know where you stand as far as pH and other nutrients are concerned.

Plants for Sweet Soil

If fixing alkaline soil isn’t an option, then adding suitable plants for sweet soil may be the answer. There are actually a number of alkaline plants, some of which may signal the presence of sweet soil. For example, many weeds are commonly found in alkaline soils. These include:

  • Chickweed
  • Dandelions
  • Goosefoot
  • Queen Anne’s lace

Once you know your soil is sweet in a given area, you still have the option of growing some of your favorite plants. Vegetables and herbs for sweet soil include:

  • Asparagus
  • Yams
  • Okra
  • Beets
  • Cabbage
  • Cucumber
  • Celery
  • Oregano
  • Parsley
  • Cauliflower

Some flowers also tolerate soil that is slightly alkaline. Try the following:

  • Zinnias
  • Clematis
  • Hosta
  • Echinacea
  • Salvia
  • Phlox
  • Dianthus
  • Sweet pea
  • Rock cress
  • Baby’s breath
  • Lavender

Shrubs that don’t mind alkalinity include:

  • Gardenia
  • Heather
  • Hydrangea
  • Boxwood

166 Wilson Road,
Middle Swan

Many gardeners are not aware of how the pH of their soil can affect the growth and health of their plants. Even what the initials ‘pH’ stand for (potential hydrogen) sounds too scientific and confusing for many people. However, you don’t need a science degree – in reality a basic understanding of the principles involved will help you out.

What pH measures is how acid or alkaline your soil is. This balance affects the plant’s ability to access and benefit from nutrients which are present in the soil. In many instances, what appear to be signs of nutrient deficiency in plants (ie. Yellowing leaves, stunted growth) are directly attributable to an incorrect pH balance.

Most plants prefer a neutral soil, which has a pH of between 6 and 7. When the pH falls below this, conditions are said to be ‘acidic’, when above they are said to be ‘alkaline’. The table below will help you see the affects of rising or falling pH on nutrient availability.

Take the element of iron for example. The thickness of the bar indicates availability, so reading off the numbers at the bottom of the chart, it is most available between the ranges of 4.0 – 6.0, and then begins to taper off slightly. By 7.5 the availability has considerably decreased.

If you rule a vertical line through the chart at around 6.5 – 7, you will notice that most of the bars representing the elements are near or at maximum thickness – meaning at optimum availability. So you can see the further off this mark – either to the acidic or alkaline sides of the scale – certain nutrients become unavailable to plants.

How pH can be tested.

Simple pH kits are available for around $30. These kits were developed by the CSIRO and last for many uses. Alternatively, at the Green Life Soil Co. we are happy to conduct a free test for you. All we need is a small amount of soil (approx. ½ a cup) taken from the top 10 – 20cms, ie. the root zone of your plants. (If we are too busy to do the test on the spot, you can leave it with us and we will let you know the results later!)

How to correct a pH imbalance.

If your soils are a little on the acidic side, adding lime (we recommend dolomite lime) at a rate of approx. 100gm/m 2 for sandy soil. (For heavier loam, 200gm/m 2, and up to 300 – 400gm/m 2 in heavy clay). It is often best to do this in 2 or 3 doses over a period of months rather than one large hit, which may be a shock to some plants.

Should your soils be alkaline, it is a little more difficult to fix the problem, but not by any means impossible. One of the fastest ways is to add sulphur, or a sulphate such as iron sulphate, at a rate of approx. 25gm/m 2 for sandy soil. (For heavier loam, 50gm/m 2, and up to 100gm/m 2 in heavy clay.) Iron sulphate can be used at approx. double the rates above, however as it will also increase salinity it should be added over a period of time and watered in well.

Often alkalinity problems can be linked to factors such as limestone soils, or even limestone or cement building structures. Sometimes problematic garden beds have a dark secret – builders rubble (cement and plaster waste) buried deep, that continue to leach lime over the years!

Adding sulphur can be a temporary fix. Adding organic matter tends to be helpful long term, particularly with things of a naturally acidic nature such as pine needles and sawdust.

To counteract alkaline soils, we also recommend Charlie Charcoal – this amazing biochar has a naturally low pH and can lower and stabilise the pH of your soil. Plus it has many other benefits to do with nutrient holding and water holding – we use it in all of our mixes @ GLSC in varying quantities, depending on the intended use of the soil.

A final word of warning! Many gardening TV shows and magazines produced in the Eastern States routinely advocate adding lime to garden soil. Remember that our soil types in the West vary greatly from those over East, so before randomly throwing handfuls about, please test your soil first to ascertain whether YOUR garden really needs it!

Also: Adding organic matter and having a healthy soil microbial life can ‘buffer’ pH meaning plants can still access nutrients. Observation of how things are growing is really the best way to see whether you have a problem. Readings which may be “too high” or “too low” are totally irrelevant if you have a booming garden (and may just be attributed to a dodgy reading)!

How to Organically Correct Alkaline Garden Soil

Step 1 – Determine the pH of Your Garden Soil

Test the garden soil at several places with the soil pH test kit. Dampen the soil where you want to take samples. Scoop out soil with a sterilized hand spade. Take soil samples from several locations in your garden, place them in the soil sample jars, labelled by their location and date obtained, and test them with the soil pH testing kit. Follow the pH testing instructions carefully.

Some spots in your garden may be more or less alkaline than others. If your soil pH tests at above 7.5 there may be an abundance of calcium carbonate in the soil. When this molecule is present in such quantity, reducing the soil alkalinity is very difficult. You may need to irrigate it for a few months after applying organic compost and mulch to lower the calcium carbonate content.

Step 2 – Prepare the Soil for Organic Correction of pH

Mark the area of your garden where you want more acidic soil with a border of wooden pegs, corded together. Remove all existing plants whether annuals or perennials, and rototill the soil thoroughly. Water the soil area to saturation and rototill it again.

Step 3 – Add Organic Compost

Add organic compost to the soil to a depth of 2 inches across the whole bed. Rototill this compost into the soil until thoroughly mixed. Organic compost in soil will help it retain its new pH level after the soil has been corrected.

Step 4 – Add Sphagnum Peat Moss

For a small garden plot of up to 100 square feet, add a 2-inch blanket of organic sphagnum peat to the top of the soil. Use the rototiller to work this peat into the top 8 inches to 1 foot of garden soil in the early spring, just before planting.

Step 5 – Add Sulfur for Large Garden Areas

For garden soil enrichment in an area over 100 square feet, elemental sulfur is safe, cost-effective and thorough, although slow compared to peat moss. Available in granular form, elemental sulfur is easy to apply to a large soil area. Use 3/10 pound of granular sulfur for each 10 square feet of soil. Mix it in well with the rototiller into the top 12 inches of soil.

Wait three months between applications of sulfur on garden areas over 100 square feet. You can also use aluminum sulfate or iron sulfate to provide sulfur to acidify the soil, at a maximum ratio of five pounds for each 100 square feet.

Ask Dan: ‘What is sweet soil? And is it good, or what?’

Hey, folks —

Hey, folks —
May is halfway over, and it’s getting to be that time of year when watering is a big concern. If the weather is sunny and dry, don’t neglect your watering. Most flowers and shrubs need about an inch of water each week to perform well, and newly planted seedlings won’t make it if their roots are allowed to dry out.
May is also a time of gardening inspirations and dreams. Look around and notice what your neighbors are growing in their gardens and what they are creating in their landscapes. Think of how you might utilize some of their ideas along with your own to make your garden just a little bit better.
Q. Hi, Dan. We recently moved into an old farmhouse, and after settling in we decided to use the old garden. When we bought the property, the previous owner said that the soil in the garden was sweet. My question is: What is a sweet soil, and is this good, or what? Please help. — Paul from Warwick
A. Usually when a person refers to a soil as being sweet, it means the soil is chalky or alkaline as opposed to being acidic. What they are referring to is the soil’s pH . A soil with a pH lower than 7.0 is an acid soil, and one with a pH higher than 7.0 is alkaline. Sweet, sour and bitter are terms to describe soil pH. Sweet soil is the mid range, or within ideal pH levels for most plants. Sour soils are acidic soil, with a low pH level. Here are some ornamental plants that prefer sweet soil:
Lilacs Clematis Virginia creeper Passionflower Sweet peas Japanese anemones Nasturtiums Zinnias Peonies Phlox
Herbs that prefer sweet soil:
Lavender Thyme Rosemary
Vegetables that prefer sweet soil:
Beets Cauliflower Cabbage Swiss chard Leeks Melons Onions Parsnips Spinach
Q. Dan, I have a bed of Asiatic lilies, and I notice that it is getting a lot of new plants real close to the mother plant. Does this mean I have to dig up the mother plants and take the babies off? Do I replant the mother plant and the babies, or just the babies? When do I do this? Thank you. — Margaret
A. Asiatic lilies are very hardy — probably the most hardy of all the lily bulbs. They do very well here in our area. Of the lilies, Asiatic lilies are the first to flower each season. They are not as fragrant as their cousins, the Oriental lilies, but do make up for it by being vigorous, multiplying fast, as well as easy to grow. The Asiatic lily bulb divides itself as it gets larger, so you will usually get a larger plant surrounded by smaller ones as you described. You can divide the bulbs away from the mother every two to three years and replant them, giving them more room to grow. As those smaller bulbs grow bigger, they will also divide and start newer, smaller daughter bulbs, and the cycle goes on.
The very best time to dig up your lily bulbs would be in the early autumn, after the foliage has turned yellow. It’s easier to find your bulbs with the stems still visible. Be sure to protect fall-dug lilies from drying out or freezing if you can’t get them replanted immediately; roots will still be fleshy. Lily bulbs do not go fully dormant and must be protected from drying out at all times.
Q. Dan, we have some hybrid poplars that we planted several years ago. They grew very fast but now are losing their bark. It seems to be just sloughing off. One tree seemed to be dead but does have some growth on it. What is causing this? — Joan H, Campbell Hall
A. The hybrid poplar tree is probably best known for its ability to grow fast and its screening capabilities. But what most people don’t realize is that these trees can be plagued by a number of different problems, causing them to have a relatively short life.
The poplar tree is extremely susceptible to a devastating canker that can cause bark to fall off and eventually kill the tree in as little as a few years. Poplars are also susceptible to fungal leaf spots that cause all the tree’s leaves to fall off by late summer. Hybrid poplars are among the fastest-growing trees in North America, however, and are well-suited for certain conditions. Poplar hybrids are not desirable in many landscapes, but they can be of major importance under certain forestry conditions.
Q. Dan, I have tiny, dark dots on the siding over much of my house. I believe I read that this might have been brought in by the mulch. I do have five beds surrounding the house. These spots are very difficult to remove; they actually have to be scraped off and they leave a stain. Before mulching again this spring, could you please advise me as to what they might be and if the mulch is the culprit? — Christine from Highland Mills
A. Christine, you have a problem with artillery fungus, a wood-decay fungus that can live and thrive on bark mulch. It commonly occurs on dead trees, dead branches and rotting wood. If infested material is ground into mulch, the artillery fungus may be already present when the load of mulch arrives at your house. Under cool, moist conditions, the fungus will grow rapidly.
People can also spread this fungus. Some homeowners make the mistake of sanding, scraping, or otherwise removing the spore masses from the sides of their houses, and letting them fall into the foundation mulch. Such spores inoculate the mulch, which then produces a new generation of the fungus.
The dark spore masses of the artillery fungus stick like Super Glue. Most people have no success removing them from a home’s siding without leaving a stain or damaging the siding, especially old, dry siding. Power washing may work on brand new vinyl siding that still has its shiny, oily sheen.
There’s nothing you can spray on the mulch to get rid of this fungus. Instead, remove all the infested mulch (just around the foundation, not further out in the yard), bag it up, and dispose of it with the trash. Then put down a layer of landscape fabric and overlay it with stone or another inorganic mulch.
Set your tomato supports in place before plants get too large. Smaller determinate varieties can be supported with small cages, but larger indeterminate varieties need large cages or tall stakes. Secure cages with stakes so they don’t topple. Lilacs should be pruned lightly after they finish blooming, removing sucker growths and dead blooms. Feed lilacs in May with a good all-purpose 10-10-10 fertilizer after they have finished blooming. If your soil has an acidic pH, work a little lime into the soil as well.
Dan Daly is a plant fanatic who has been gardening since childhood. With more than 10 years in the business, he’s ready to answer all your gardening questions. E-mail him at [email protected] or send to Ask Dan, Times Herald-Record, 40 Mulberry St., Middletown 10940.

The Perils Of Peat Moss

What is Peat Moss?

Peat moss comes from bogs, which are water-saturated, oxygen poor environments. Because of the lack of oxygen and the resulting low level of soil microbes, peat moss is made up of partially decomposed dead vegetation. In colder climates, peat moss is generally comprised of partially decomposed mosses. Partially decomposed tree material is the basis of peat moss in tropical climates.

Unlike finished compost, which is “all good,” peat moss can be good or bad.

The Good Aspects of Peat Moss

Peat moss is readily available at virtually all garden centers. It’s lightweight, and relatively inexpensive. Peat moss is generally sold in bales that contain from 1 to 4 cubic feet of material per bale, and you can buy a large quantity of it for very little money. A 3 cubic foot bag will generally cost about 10 bucks.

Peat moss will dramatically improve water absorption in sandy soils; it will improve air circulation in clay soils; and, it can improve the tilth of both sandy and clay soils.

Peat Moss will usually lower the pH of garden soils, and can be helpful where the soil is too alkaline for the intended crop. Blueberries, which perform much better in acidic soils, will usually benefit from the addition of peat moss. And, peat moss can be used to encourage pink hydrangea flowers to turn blue.

The Potentially Bad Aspects of Peat Moss

As noted above, peat Moss has an acidic pH, generally in the range of 4.4 (a pH of 7 is neutral; higher pH numbers indicate alkaline soils). If your soil is already acidic, adding peat moss will probably make it less productive for most plants (blueberries, azaleas, and other “acid-loving” plants being the possible exception).

Peat moss is also very dusty; in addition to being messy, peat moss can irritate your lungs. The shape of the very small particles is such that the fibers can actually stick to the insides of your lungs for a while … not a very pleasant situation! If you decide to add peat moss to your garden, try to do so on a very calm day, wear a respirator, and till it in as soon as you can.

Uses for Peat Moss

In addition to being used as a soil additive where appropriate, peat moss is the primary component of most “soilless” mixtures that are commercially sold for seed starting and houseplant potting. These mixes usually also contain pearlite, vermiculite, and added nutrients. Many mixes also contain a wetting agent, as dry peat moss – in spite of its ability to hold and absorb water – will initially repel water. If you’ve ever started seeds in a soilless mix, you’ve probably noticed that water will initially stay on the surface of the dry medium. When I use soilless mixes for seed starting, I prepare small batches in a bucket or mixing tray by kneading the water into the mix by hand. Wear a paper or foam respirator – it may look silly, but your lungs will thank you.

Some gardeners have successfully grown tomatoes in bales of peat moss. You can simply cut an opening in the middle of the broad side of the bale, and insert a tomato plant seedling. Of course, since the peat moss is acidic and practically void of nutrients, you’ll need to feed the plant with a good balanced fertilizer.

Peat Moss and the Environment

There has been some ongoing discussion about whether or not the use of peat moss is environmentally responsible. Peat moss is a renewable resource. But, peat bogs are also very efficient as “carbon sinks” and may play an important role in controlling global warming. Well over 90 percent of the peat moss used in the United States comes from Canada, and thankfully, the Canadian Sphagnum Peat Moss Association (CSPMA) emphasizes sustainable harvesting methods. So, it’s unlikely that the bogs will be depleted any time soon.

Peat Moss and Your Compost Pile

Don’t add large quantities of peat moss to your compost pile or bin. It won’t help, and large quantities will probably hurt. You don’t need to obsess about removing the small remnants of peat moss that may still be visible around the root systems of plant material that you add to the compost at the end of the growing season, but a well-maintained compost pile doesn’t need peat moss to perform.

For more information on composting, go to

If you have any comments, I’d really like to hear from you.

OZ Gardener
The Garden Of Oz

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Read Reviews (8)
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March 4, 2013

By: sherry franklin

thank you i wished i had read your article before i applied ; because no masks were warn during appliacation.

February 22, 2013

By: Linda

Good article except peat moss and sphagnum moss are not really the same. Sphagnum moss (the fluffy green stuff) is renewable but peat moss (crumbly brown stuff) is the dead highly compressed sphagnum moss that is on its way to becoming burnable peat in a few thousand years. Peat moss is NOT a renewable resource. It accumulates at a rate of approx 1mm/year.

February 18, 2013

By: Liz F

Seems to be good gardening stuff, lots of info, easy to read. Thanks!

September 15, 2012

By: linda

Thanks for the heads-up about peat moss. I have a lung condition, and didn’t know the effects this is having on me . great article ,keep up the good work.

July 25, 2012

By: joann

I have a question. If peat moss is water repellent
and you add to clay soil what happens if it is very dry, cause clay cracks and if peat moss doesn’t allow for water to absorb then what

April 30, 2012

By: GardenerB

Finally! A page to actually answer my questions and give well thought-out information that is not just one sided.

May 4, 2009

By: Ginger

Great article! I didn’t know that peat moss stuck to my lungs if I breathed it in. I’ll be sure to wear a dust mask when I garden with it…I was wondering why I was breathing weird after planting.

April 3, 2009

By: homes-n-gardens

Thank you!

Soil pH in The Home Garden

Iowa soils are very diverse and so are the chemical characteristics that make up these soils. Soil pH is one property that can vary widely across the state both naturally and due to crop production inputs. It is also one of the most cost effective and easy to manage soil properties that can be modified to improve plant health and crop production.
Soil pH affects the availability of nutrients for plant uptake. They may become more available for pant uptake or less available depending on soil pH. For instance, the mircronutrients iron, manganese, and zinc become more available as pH decreases but molybdenum becomes less available. In Iowa, micronutrient deficiencies such as iron or zinc are often due to above optimum soil pH and can be corrected by reducing the soil pH rather than adding additional micronutrients to the soil.
Soil pH is the measure of concentration of hydrogen atoms in solution. The scale has a range from 0 to 14. Less than 7 is acidic, 7 is neutral, and greater than 7 is considered alkaline or basic. As the soil pH increases, the number of hydrogen atoms decreases. However, the scale is not linear. Soil with a pH of 5.5 is 10 times more acidic than soil with a pH of 6.5 and 100 times more acidic than soil with a pH of 7.5. It is important to remember the scale is not linear when adding amendments to modify soil pH. When modifying soil pH, doubling the amount of sulfur or lime will not double the change in soil pH.
Most soils in Iowa have a pH between 5.5 and 7.5, however Iowa soils can be as low as 4.5 or greater than 8.2. The ideal range for most plants grown in Iowa is 6.0 to 7.0 but some plants like blueberries and azaleas prefer more acidic soils and others like lilac, peony, and salvia prefer more alkaline soils. Further complicating the issue, soil pH is not a static condition; it can change over time due to fertilization practices, irrigation, or natural weathering. Because of the broad range of soil pH found across Iowa and the varying needs of plants, gardeners and farmers often must adjust the soil pH for optimum plant growth and production.
Soil pH is easily modified in most soils using sulfur or lime. However, before attempting to modify the soil, collect a soil sample to determine the existing soil pH and buffer pH. These soil properties are essential components to making informed decisions about amending soil pH. Directions for collecting a soil sample can be found in the extension publication Soil Sample Information Sheet for Horticulture Crops ST0011 via the Iowa State University Extension Store.
It is absolutely necessary to make soil pH changes before planting. Lime and sulfur, amendments used to increase and decrease soil pH, respectively, are not water soluble and need to be mechanically incorporated into the soil with a tiller, shovel, or disk to a depth of 6 to 8 inches. Once plants are in the ground, it is nearly impossible to make further corrections without disturbing the root system nor is it reasonable to amend the soil below a 6 to 8 inch depth. Allow the soil time to change. This is not an instantaneous process and may take weeks or months. When making significant changes to the soil pH before planting perennial crops, it is best to amend the soil, wait 6 months, and recheck the soil pH.
Decreasing the Soil pH
Elemental sulfur and aluminum sulfate are the most common amendments used to decrease the soil pH. Elemental sulfur is the safest option to decrease soil pH; it is relatively inexpensive and available via local agriculture suppliers and garden centers. Unfortunately, it is slow to react. Elemental sulfur must go through two processes, a biological process and a chemical process, before soil pH is decreased. This often takes 3 to 6 months of warm soil temperatures when soil biology is active. Aluminum sulfate reacts in the soil very quickly as it must only undergo a chemical process. The change in pH happens within days or weeks. However, aluminum sulfate is not an ideal amendment because requires more material than elemental sulfur to reduce the soil pH and aluminum is toxic to plants.
Soils that are naturally high in pH or highly buffered will tend to return to their natural state. Ammonium sulfate is sometime used by commercial growers on these soils because it is somewhat soluble and may also be used as an annual nitrogen source. It is intended as a safeguard to help hold the soil pH down within the desired range. It is not an effective means at reducing the soil pH post planting nor should it be used to decrease the pH preplant. Other fertilizers such as diammonium phosphate, monoammonium phosphate, and urea are acidifying agents that may decrease pH over time or help hold pH down on naturally high pH soils. These fertilizers should not be used to decrease the soil pH, but are often responsible for the gradual decrease in soil pH in commercial agriculture fields.
Sphagnum peat moss is often suggested as a soil amendment to decrease soil pH. However, most peat moss found in garden centers is neutral or slightly acidic. Only Canadian sphagnum peat moss has a low pH of 3.0 to 4.5 and will effectively reduce soil pH. Canadian sphagnum peat moss is best used in addition to sulfur applications when building raised beds for acid-loving plants or when large pH adjustments are required.
Three pieces of information are required to determine how much sulfur is necessary to decrease the soil pH: Current pH (from a soil test), target pH (what you want the pH to change to), and soil type. Table 1 indicates how much pure elemental sulfur is required per 1000 sq ft to decrease the soil pH based upon the existing pH, the target pH, and soil type.
Table 1: Pounds of sulfur required to decrease soil pH to a depth of 6 inches per 1000 sq ft.

Increasing the Soil pH
The pH of acidic soil can be raised by incorporating limestone into the soil. Most limestone found in Iowa is a mix of calcium and magnesium carbonate although the ratios will vary. Limestone is slow acting but it is relatively inexpensive and safe to use. Hydrated lime is more reactive and will increase the soil pH faster than lime, however it is dangerous to work with.
Two pieces of information are required to determine how much lime is necessary to increase the soil pH: current buffer pH (from a soil test) and target pH (what you want the pH to change to). Note that the lime table requires buffer pH and not the soil pH from a soil test. Buffer pH results are only provided on a soil test report when liming might be needed as determined by the soil lab. Table 2 lists lime recommendations in pounds of pure fine calcium carbonate per 1000 sq ft to increase soil pH from its present level to pH 6.5 or 6.9 to a depth of 6 inches. When bulk agricultural lime is used, additional adjustment are required to correct for particle size and purity.
Table 2: Pounds of lime required to increase soil pH to a depth of 6 inches per 1000 sq ft.

From Table 14 of extension publication Crop Nutrient and Limestone Recommendations in Iowa PM 1688 via the Iowa State University Extension and Outreach Store.
Gypsum is a calcium and sulfur fertilizer that produces no net change on soil pH. It is often used as a fertilizer to supply additional calcium or sulfur to the soil when no pH change is desired.
Modifying soil pH is a slow process that requires patience. Always begin the process with a good soil sample to determine the existing soil pH, buffer pH, and cation exchange capacity. Apply the required amendments and incorporate into the soil as outlined above. If planting perennial plants, recheck the soil pH three to six growing season months later to verify that the soil pH has reached the desired range. If it has not, additional amendments may be necessary.
Commercial fruit and vegetable growers are encouraged to see Managing Soil pH in Horticulture Crops at

Folks are always wanting to do the impossible. “Impossible” in this
area consists of trying to change the alkaline soils in this area to
acidic or even neutral. Novices always try to change or modify the
local soil pH in an effort to grow their favorite gardenia or azalea.
The results are always the same — failure.

The alkalinity problem can be treated or temporarily altered.
The temporary alteration involves elimination of the culprit causing the
problem – the soil. If extremely acid-loving plants such as azaleas or
gardenias are to be grown, an artificial growing media should be used.
Standard potting soil is not acid enough and will not maintain an acid
condition over a long period of time with the alkalinity bombardment of
water and soil leachings. To insure an acid-enduring growing media,
mix two-thirds sphagnum peat and one-third WASHED sand (not regular sand
since it contains lime and weed seed). Excavate a suitable (large
enough to contain the root system of the mature-size plant which you are
planting) size hole, and fill with the sphagnum-peat-sand mix. DO NOT
a lot of trouble but it prevents a lot of ugliness later. Many rose
growers follow a similar plan of action to insure vigorous plant growth.
And, if you don’t make this “modification BEFORE you plant, don’t
expect to correct the problems later!

Of course, the choice of peat moss may make the difference between
success or failure. One has to be careful of the kind of peat moss he
or she uses to alter the soil horror with which we must contend.
There are three major types of peat moss in the trade. They are
moss-peat (peat moss), reed-sedge peat, and peat humus. Peat is the
organic remains of plants accumulating in swamp areas where ordinary
decay has been retarded by immersion in water. It may require from 100
to over 500 years to produce a layer of peat a foot thick. The rate
depends on the type of plant and its environment. Moss-peat (peat
moss) is formed chiefly from the sphagnum type mosses. Nearly all peat
imported from Canada or Europe is derived from sphagnum moss. It is
very acidic with a pH of 3.6 to 4.2. The color is tan to brown. Moss
peat is light weight, porous, high in moisture-holding capacity but low
in nitrogen (0.6 to 1.4 percent). It is an excellent soil conditioner
but will require some lime when used to grow anything other than
acid-loving plants in containerized or container-like (such as the
excavated hole) situations.

This is what we need in South central Texas — something
that is inherently acid and will release acid gradually as it
decomposes. Because sphagnum peat moss is so extremely acid, it cannot
be neutralized by the constant bombardment of alkalinity which is
experienced in local soils. The pH of most landscapes ranges from 7.8
to 8.2. Organic material (leaves, grass clippings, tree trimmings)
produced locally, grown in alkaline soil, will produce a more basic or
alkaline decomposed product. So to “fight off” the onslaught of
alkalinity, an organic material produced in an area which has acid soils
MUST be used.

So why is pH so important? When the pH of a soil is too
high (alkaline) or too low (acidic), most of the minor fertilizer
elements (iron, manganese, molybdenum) become unavailable for plant
uptake. Plants must have the minor elements, especially iron,
Iron deficiency in plants is a problem common to many landscapes due to
our very alkaline soil. For further information about lawn
fertilization, see:

Iron is essential for the formation of chlorophyll (the green
pigment in plants). Therefore, when iron is unavailable to the plant,
iron deficiency (sometimes referred to as iron chlorosis) results.
Prolonged iron deficiency can result in decreased shoot and root growth
because of a lack of chlorophyll to maintain photosynthesis. Iron
deficiencies do not usually result from a lack of iron but rather
because the iron is tied up or “fixed” in insoluble compounds. Iron is
most commonly deficient in alkaline soils although excessive levels of
phosphate, manganese, zinc and copper can produce iron deficiency.
Waterlogged soils can also reduce the availability of iron.

Identification of the problem is not difficult. Look for two

1) Progressive yellowing of the newest leaves occurring first. If
lower, older leaves turn yellow first, then the problem is something
other than iron deficiency.

2) Leaves with darker green veins and the tissues between the
veins turning yellowish green. When iron deficiency is severe the
entire leaf may become white and finally brown.

Iron chlorosis is most prevalent on members of the grass family
(such as St. Augustine even though some varieties such as Floratam are
more resistant), certain fruit trees (citrus and peaches), many
vegetables (particularly beans), many flowers and ornamentals, and some
shade trees. Plants that thrive in acid soil, such as azaleas or
gardenias, can likewise be severely affected. Since iron deficiency is
often the result of alkaline soil reactions, acidifying soils would
appear to be a practical solution. Calcareous soils, however, may have
large reserves of calcium to buffer attempts to lower the pH,
particularly if the soil is fine textured.

To prevent a plant’s suffering the fate of “iron poor blood”, use
the following techniques:

1) Totally avoid the perpetual problems with yellowing foliage of
plants by planting only Extension recommended, tried-and-proven plant
types. Lists of recommended ornamentals are available at:

2) Add iron. The best approach to correct the yellowing
condition of existing plants is to use either chelated iron or iron
sulfate (Copperas) as both a soil treatment and as a foliar spray.
Spray applications of sulfates and chelates often are more effective and
give quicker results than soil applications. However, the effect will
normally not be as long-lasting and repeat applications may be
necessary. Be certain to keep any iron products off walks, driveways,
brick or masonry surfaces, since they will cause staining. MALCOLM
BECK OF GARDENVILLE ADDS: “Fresh iron stains on a sidewalk or anywhere
can easily be cleaned up with oxalic acid. Gardenville sells it or it
can be purchased at some True Value stores. It is normally used to
bleach wood. It will not hurt plants and works really good on FRESH
iron stains.” Soil applications of iron sulfate to green a lawn
that is yellow and suffering from iron chlorosis MUST be made
uniformly and concisely to avoid foliage burn and stripping. When using
a drop-type spreader, be sure to overlap wheel paths on passes through
the area being treated, walk at a rapid, steady rate (to avoid overdoses
of the free-flowing, granular iron sulfate). Water the iron
sulfate-treated area after the application has been made.

The good news is that there is now a granulated, i.e., doesn’t
pour through the spreader as Copperas does, product which contains the
same percent iron as Copperas and has the nitrogen fertilizer to
provide a quick green-up. It is sold as Ironate (NOT Ironite which has
not been effective in my tests! and is said to contain arsenate since it
is a mined product.)

Iron chelates are expensive and some commercially formulated
types don’t perform well in alkaline soils. Malcolm Beck and I
discovered a way for homeowners to make their own iron chelate. An iron
chelate is an piece of organic material with the iron molecule tightly
attached. As the organic material decomposes, the iron molecule is
released into the soil for use by the plants. So, basically, an iron
chelate is a slow-release iron source. If you can imagine how easily
and completely iron products will stain walks, driveways, brick or
masonry surfaces, you can readily see how those iron molecules can
quickly attach to an organic product (carrier) such as leaves, grass
clippings, mulch, lawn dressings, etc. From this notion years ago we
began to recommend that gardeners make their own iron chelate product.
This can be simply done by spreading iron sulfate, in the form of
Copperas or the new improved version with nitrogen named Ironate, onto
and into organic mulches. This should be done in layers and every time
organic material is added. How much to add? Add it until the top of
each layer of the organic material is darkened — it would be difficult
to add too much since the soil deactivates the iron molecule so rapidly.
If you need a measurement, mix one cup of iron sulfate (copperas or
Ironate) to each bushel of mulch applied.

A COMMENT FROM MALCOLM BECK: “The best product I have discovered to
grow plants and keep them green is Green Sand. I introduced Green Sand
to this area and it contains from 10 to 20 percent iron. It is a
naturally occurring mineral found in Texas. The Green Sand should be
applied to a garden area at the rate of two pounds per 100 square feet
and to lawn areas at the rate of 15 pounds per 1000 square feet. It
will not burn so additional amounts can be added to severely chlorotic
Gardenville is selling SAWS compost mixed with Greensand and being
sold as Sports Turf Plus.”

If you have the concept of how to cure yellowing, chlorotic
lawns by the addition of iron and nitrogen, how would you like to cure
certain fungus diseases as well? Dr. Phil Colbaugh and
Research-Extension colleagues at the Texas A&M Research Center at Dallas
have discovered that using a top-dressing or lawn dressing with the acid
peat moss (Michigan Peat or Peat Compost) results in control of TAKE-ALL
on St. Augustine grass on Dallas area home lawns. In comparison
studies, peat moss topdressing reduced symptoms of TAKE-ALL ROOT ROT
for longer periods than cow manure compost and is thus considered the
more effective disease control product.

In recent years we have discovered that underground organs of turf
grasses are commonly attacked by ectotrophic fungi that cause
destructive patch diseases. Ectotrophic fungi grow over living turf
grass roots and underground stems as runner hyphae (dark fungal
threads). There are several ectotrophic fungi that cause turf grass
diseases and their appearance is similar on the different turf grass
hosts they attack. For convenience, all of these fungi are referred to
as ETRIF (ectotrophic root infecting fungi) to simplify their diagnosis
and associations with the similar turf diseases they cause.

Take-all root rot (TARR) of St Augustine grass has emerged as a
major problem on landscapes in Texas as well as other states along the
Gulf Coast including Florida. The disease is caused by Gaeumannomyces
graminis var. graminis, which belongs to the ETRIF pathogen group. The
brown-black mycelial growth of the fungus (Fig.1) colonizes roots,
stolons and shoots but it is primarily a root destroying pathogen.
Damaging effects of this disease on St. Augustine grass were first
observed and described in Texas by Dr. Joseph Krausz (plant pathologist
at Texas A&M University) and in Florida by Dr. Monica Elliott
(University of Florida). In a 1999 survey of St. Augustine grass lawns
in north Dallas, we observed yellow patch symptoms (Fig. 3) of the
disease on 61% of 70 lawns during the month of September. If this
disease progresses it kills the stolons and produces patches of dead
grass during summer ranging from 3-10 ft in diameter. Because of the
widespread nature of this disease, our research investigations sought to
develop a practical control measure for landscapes with St. Augustine
grass lawns.

Symptoms of take-all root rot disease (TARR) typically appear on
St Augustine grass as diseased patches of turf during late spring and
throughout the summer months. Pathogen activity causes a severe root rot
that completely destroys tap roots which anchor St. Augustine grass
stolons to the ground. Visual symptoms of the disease on lawns are
initially small yellow patches of turf with leaf blades that appear
chlorotic while the healthy leaves remain a typical green color (Fig.
3). The yellow patches are thought to be associated with the production
of a toxin by the ETRIF fungus when the turf is growing under stressful
conditions. Yellows symptoms of the disease can persist on lawns
throughout the summer growing season. Dark brown or black mycelial
threads of this fungus (Fig. 1) are distinctive and produce scattered
black dots (hyphopodia) that anchor the fungus to the plant. Roots of
affected plants become shortened, discolored, and often have dark
colored lesions that are visible upon inspection with a hand lens.
Eventually the roots become completely rotted and shriveled to form a
non-functional root system (Fig 2). In the final stages of decline,
diseased stolons gradually succumb to hot summer temperatures or cold
winter weather and produce large patches of dead grass that do not
recover from injury.

Affected patches of turf can at first be quite small ranging from
1-2 feet in diameter; however, they also appear as larger areas that can
range from 5-10 feet in diameter. Diseased areas are not always circular
but often appear as roughly circular patterns in the lawn. In our 2002
TARR survey on North Dallas lawns, we observed a higher number of
take-all symptoms in heavily shaded areas compared to areas receiving
direct sunlight or partial shade for most of the day (Fig. 5). TARR
disease should not be confused with white grub damage which can also
appear at the same time of the year. The best clue is to look for the
yellow or chlorotic leaf extensions (fig. 3) on St. Augustine grass turf
that has not received mowing for several days. Symptoms of TARR disease
also include the appearance of brown shriveled roots that are killed by
the fungus as opposed to white grub damage where the roots are actually
removed by insect feeding.

We used two approaches to control the TARR disease in field
investigations on area lawns during the past three years.

One approach utilized conventional fungicide sprays with
Terraguard or Bayleton, Heritage, and Banner Maxx using 2.9L of spray
per 10 m2. A second approach utilized topdressing lawn care products
including (1) manure compost and (2) sphagnum peat moss. Manure products
can enrich the microbial number and diversity for variable lengths of
time and low pH products like peat moss had been shown to suppress the
Gaeumannomyces fungus in previous research. While some of the manure
based topdressing regimens demonstrated improved turf grass growth,
effects on disease control were only partial and limited in duration.
Research field plots with the fungicides Terraguard (4 – 8 oz) or
Bayleton (2 oz) treatments gave good results for controlling the
take-all root rot symptoms. Success with fungicide treatments was better
on a lawns maintained under shaded conditions compared to lawns in full

A second approach with topdressings used low pH topdressing with
sphagnum peat moss. This topdressing approach has consistently
demonstrated TARR disease suppression in field studies during the past
two years. Our field comparisons of manure compost vs. peat moss
topdressings indicate the peat moss to be a more effective long-term
approach for reducing symptoms of the TARR disease. Some of the older
research literature on the fungus causing TAP indicates its aversion to
low pH. This might explain how the peat moss (pH = 4.4) controls the
fungus on exposed stolons and roots where the disease is active.

There is no indication of varietal resistance to take-all root rot
since the disease has been noted on all of the commercial St. Augustine
grass varieties. The use of fungicide applications is also limited with
only a few fungicides that are approved for use on this disease.
Although there is good evidence that fungicides are capable of
controlling the disease, environmental conditions and vigor of the turf
may pose some limitations on the effectiveness of fungicide treatments.
At this time we have no explanation as to why we observed a lack of
uniformity in fungicide effectiveness on different lawns.

The use of organic topdressing to control turf grass disease is a
relatively new approach to controlling turf grass diseases. Because of
the complexity of microbial antagonism, fertility values of topdressing
materials, different types of diseases and susceptibility of pathogens
to pH, most of this type of research is directed by trial and error
experimentation. We do have good evidence that the acid peat moss
topdressings result in control of TARR on St. Augustine grass on Dallas
area home lawns. In comparison studies, peat moss topdressing reduced
symptoms of TARR for longer periods than cow manure compost and is thus
considered the more effective disease control product. Additional
research will address the best time to apply peat moss topdressing
products as well as possible effects on other turf grass pathogens and

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