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Three Easy Soil pH Test Methods

Why do a Soil pH Test on your garden soil? Your soil’s pH can have a profound affect on what nutrients are available to your plants.

This is especially important for those of your using synthetic fertilizers to feed your crops. If you are already using compost and working with your soil’s biology you might find the pH of your soil is adjusting to perfection without you.

So the ph tests are either vital or just plain interesting and fun…

Soil pH testing is done to see how acidic or alkaline your soil is. pH means potential Hydrogen. It measures the number of H+ ions in the soil water.

It’s a logarithmic scale that goes from 0 to 14. A pH of 7 is considered neutral and most plants prefer something around 7 or just a little lower or acidic. Anything under 7 is acidic with 0 being with 0 being most acidic, 7 being neutral and 14 being most alkaline. Because it’s a logarithmic scale each jump is a ten fold increase so a soil with a pH of 5 is 10 times more acidic than one with a pH of 6 and a 100 times more acidic than one with a pH of 7.

Acidic or Alkaline?

You can of course send a sample of your soil to a lab for a pH test but then you couldn’t pretend to be a scientist or a CSI.

Here is a quick and simple way to test if your soil is acidic or alkaline.You’ll need your soil, some vinegar, distilled water, and baking powder.

  • Take a small handful of soil and rub your hands with it. This will clean off anything on your hands that might affect the soil.
  • Take another clean handful of soil. Wet the soil with vinegar. If it fizzes and bubbles you have alkaline soil.
  • Take another clean handful of soil. Add baking powder and then wet the soil baking powder mix with distilled water. If it fizzes your soil is acidic.

Now you have a bit of info and you probably want to know how acidic or alkaline your soil is.

pH Soil Test with pH Paper

When I first looked at soil pH test options I figured you had to buy a soil pH test kit to test soil. However I have since discovered that a whole range of pH test strips including those for urine and saliva, for aquariums, and for water should be just dandy for testing soil. Here are a couple of examples of test strips and rolls of pH paper that would be suitable and are available from Amazon.

When you look for pH test strips you need to notice the pH range they test. Many strip or rolls of test paper say they are universal and test from pH 1 to 14. This would be fine. Some however test a smaller range. Ideally you want test paper that includes pH from 4.5 to 10 for soil testing.

To use the test strips:

  • Rub your hands with a small handful of soil to clean off anything on your hands that might affect the soil.
  • Take a small handful of soil and wet it thoroughly with distilled water. You could also use a plastic lid to mix the soil with distilled water.
  • Touch the test strip to the water and soil mixture and wait for the color to change.
  • Compare the color to the color chart that comes with strips. Take the reading from the area that is closer to the soil rather than further away where the water wicks up to.

Here is a video with a detailed closeup of someone doing a pH test using pH test strips. It starts off with the gentleman shaking a soil water slurry. This slurry is made with equal volumes of soil and water. When measuring your soil don’t include rocks or vegetation.

Use a Soil pH Meter

Here is a possible pH meter and a soil testing kit. There are a number of suitable choices available through Amazon.

To use a pH meter you simply plunge the rod into the damp soil and a needle will jump to the approximate pH reading for your soil. It takes about a minute. Make sure the soil is damp or you will not get a reading.

What I like about the meter is you can take a lot of readings with the only expense once you have the meter being your time. You may want to add some of the text strips so you can check to be sure your meter is accurate.

What might you want to check? See what the difference is in

  • the root zone of your crops,
  • in the root zone of some weeds,
  • in the root zone of your lawn,
  • where you used compost
  • where you have bare soil

The second way is with indicator agents. Your kit will come with detailed instructions. The one pictured above can do 20 pH tests but is also good for testing NPK – Nitrogen, Phosphorus and Potassium.

The most important thing is to use distilled water for everything you need to wet as your tap water may skew your results. The process of doing these kinds of tests for your soil is very fun and one you can share with your kids. Even those not too crazy about science will like the process.

What’s next…

If you missed our Soil pH Primer check it out. Here you’ll find details on how soil pH affects plants.

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It’s no secret that soil is the most important part of the garden. Not only does it create healthy plants, or lead to their demise, but it is also full of information that can help us grow a better garden. This at-home soil pH test will give you a general idea of the pH of your soil. If you want to find out the exact pH level, you will need a test kit.

Materials:

  • Distilled Water (because it has a neutral pH. You can use regular water, but it could affect the outcome)
  • White vinegar (an acid)
  • Baking soda (a base or alkaline)
  • A bowl and spoon

Let’s Test Soil!

Scoop up a small amount of soil from an area in your garden.

Mix in a bit of water to the soil: enough to make a loose mud.

Pour a little bit of vinegar to the bowl. If it fizzes up, the soil is alkaline. As you can see, there was no fizz in my soil pH test, which would suggest that my soil is acidic.

To double-check the results, grab another scoop of soil, wet it with the water and mix again. Then sprinkle baking soda in it and mix. If it fizzes, the soil is acidic.

On the second soil pH test, my soil did fizz up, which means the soil is acidic.

You certainly do not have to perform both tests to determine the pH of your soil. Just one will suffice, but you can try both to confirm the results if you like. To be honest, I already knew that my soil is acidic, but in the name of garden science I had to confirm!

Now that you are armed with this basic knowledge about your soil, you can use it to do cool things like change the color of your hydrangea!

Acidity and Alkalinity

by Tim Loftus

Acidity levels in wastewater indicate its corrosive properties and can take a leading role in regulating biological processes as well as in chemical reactions (such as chemical coagulation and flocculation). Alkalinity, too, contributes to the properties of wastewater, many of which also affect biological processes (such as nitrification) and chemical reactions.

While both acidity and alkalinity are related to pH, they should not be confused with pH, nor should the terms be used interchangeably. Acidity is a measure of a solution’s capacity to react with a strong base (usually sodium hydroxide, NaOH) to a predetermined pH value. This measurement is based on the total acidic constituent of a solution (strong and weak acids, hydolyzing salts, etc.) It is possible to have highly acidic water but have moderate pH values. Likewise, the pH of a sample can be very low but have a relatively low acidity. Acidity is similar to a buffer in that the higher the acidity, the more neutralizer is needed to counteract it.

Alkalinity is the measure of a solution’s capacity to react with a strong acid (usually sulfuric acid H2SO4) to a predetermined pH. The alkalinity of a solution is usually made up of carbonate, bicarbonate, and hydroxides. Similar to acidity, the higher the alkalinity is, the more neutralizing agent is needed to counteract it. In general, a treatment plant and its collection system operates better with wastewater lower in acidity and higher in alkalinity.

According to EPA sampling and preservation guidelines, samples for both acidity and alkalinity measurements can be collected in glass or plastic bottles and stored at 4 degrees Celsius for up to fourteen days. However, sample handling probably plays a much more important role in preserving the integrity of the sample. Acidity and alkalinity are greatly affected by exposure to the atmosphere. Large surface areas or long contact times with the atmosphere, both in the sample container and during analysis, can either dissolve gases into the sample or allow dissolved gasses already in the sample to escape thereby changing the measurements. When sampling for acidity and alkalinity, it is best to leave no headspace in the container. Also, don’t filter the sample (which creates high turbulence) or leave in an open beaker on the lab bench for hours. Pour an aliquot just before analysis so that you minimize exposure to the air. During analysis, keep mixing turbulence to a minimum. These measures are particularly important when determining low levels of acidity or alkalinity.

Acidity and alkalinity analyses each comprise of a simple titration. Basically, acidity is determined by titrating the sample with sodium hydroxide to a pH of 8.3 (often called the phenolphthalein acidity – this term dates back to the time before electronic pH meters). Alkalinity is determined by titration with sulfuric acid to a pH of 4.5. While these pH end-points are common in wastewater situations, other end-points are often used depending on certain test or sample conditions. Also, since both acidity and alkalinity are not analyses for specific chemicals but rather represent a solution’s specific properties, its measurements are equated with an equivalent amount of calcium carbonate. This is done so that measurements of different samples can be compared to each other. Therefore, always report acidity and alkalinity measurements as “___ mg CaCO3/L to pH ___.” The mathematical formulas for calculating acidity and alkalinity, as well as descriptions of certain instances where sample pretreatment is necessary, can be found in Standard Methods.

In conclusion, acidity and alkalinity testing is easy to perform. And with careful sampling you will be far on your way toward accurately monitoring the effectiveness of your district’s domestic water corrosion control, monitoring part of the nitrification process in your facility’s activated sludge, or even troubleshooting the chemical addition process for phosphorus removal in the final effluent.

The recommendations in this article for acidity and alkalinity analyses are very general. Always check your state and local regulations. You may have additional requirements to meet.

If you have any questions, suggestions, or comments, please contact LPC Chair Paul Fitzgibbons at (401) 222-6780 ext 118 ([email protected]) or Tim Loftus at (508) 949-3865 ([email protected]). You can also visit our website at newea.org. Once on the website, press the Lab Practices button.

North American Journal of Aquaculture

Measurements of pH, acidity, and alkalinity are commonly used to describe water quality. The three variables are interrelated and can sometimes be confused. The pH of water is an intensity factor, while the acidity and alkalinity of water are capacity factors. More precisely, acidity and alkalinity are defined as a water’s capacity to neutralize strong bases or acids, respectively. The term “acidic” for pH values below 7 does not imply that the water has no alkalinity; likewise, the term “alkaline” for pH values above 7 does not imply that the water has no acidity. Water with a pH value between 4.5 and 8.3 has both total acidity and total alkalinity. The definition of pH, which is based on logarithmic transformation of the hydrogen ion concentration (), has caused considerable disagreement regarding the appropriate method of describing average pH. The opinion that pH values must be transformed to values before averaging appears to be based on the concept of mixing solutions of different pH. In practice, however, the averaging of values will not provide the correct average pH because buffers present in natural waters have a greater effect on final pH than does dilution alone. For nearly all uses of pH in fisheries and aquaculture, pH values may be averaged directly. When pH data sets are transformed to to estimate average pH, extreme pH values will distort the average pH. Values of pH conform more closely to a normal distribution than do values of , making the pH values more acceptable for use in statistical analysis. Moreover, electrochemical measurements of pH and many biological responses to are described by the Nernst equation, which states that the measured or observed response is linearly related to 10-fold changes in . Based on these considerations, pH rather than is usually the most appropriate variable for use in statistical analysis.

Received November 2, 2010; accepted February 7, 2011

Acidity, net acidity, and net alkalinity are widely used parameters for the characterization of mine drainage, but these terms are not well defined and are often misunderstood. Incorrect interpretation of acidity, alkalinity, and derivative terms can lead to inadequate treatment design or poor regulatory decisions. We briefly explain derivations of theoretical expressions of three types of alkalinities (caustic, phenolphthalein, and total) and acidities (mineral, CO2, and total). Theoretically defined total alkalinity is closely analogous to measured alkalinity and presents few practical interpretation problems. Theoretically defined “CO2- acidity” is closely related to most standard titration methods used for mine drainage with an endpoint pH of 8.3, but it presents numerous interpretation problems, and it is unfortunately named because CO2 is intentionally driven off during titration of mine-drainage samples. Using the proton condition/massaction approach and employing graphs for visualization, we explore the concept of principal components and how to assign acidity contributions to solution species, including aqueous complexes, commonly found in mine drainage. We define a comprehensive theoretical definition of acidity in mine drainage on the basis of aqueous speciation at the sample pH and the capacity of these species to undergo hydrolysis to pH 8.3. This definition indicates the computed acidity in milligrams per liter (mg L-1 ) as CaCO3 (based on pH and analytical concentrations of dissolved FeIII , FeII , Mn, and Al in mg L-1 ): Aciditycomputed = 50. (10(3-pH) + 3.CFeIII/55.8 + 2.CFeII/55.8 + 2.CMn/54.9 + 3.CAl/27.0) underestimates contributions from HSO4 – and H+ , but overestimates the acidity due to Fe3+. These errors tend to approximately cancel each other.

We demonstrate that “net alkalinity” is a valid mathematical construction based on theoretical definitions of alkalinity and acidity. We demonstrate that, for most mine-drainage solutions, a useful net alkalinity value can be derived from: 1) alkalinity and acidity values based on aqueous speciation, 2) measured alkalinity – computed acidity, or 3) taking the negative of the value obtained in a standard method “hot peroxide” acidity titration, provided that labs report negative values. We recommend the third approach; i.e., Net alkalinity = – Hot Acidity.

Best Soil Test Kit

Soil Test Kit Reviews

A lot of people start planting and gardening without really taking the time to test their soil. Many have overlooked the importance of this simple yet essential step. The truth is, the use of a soil test kit can dramatically improve your garden. A soil test kit is used to accurately determine the balance of alkalinity and the acidity of your soil as well as the quantities of the nutrients such as phosphorus, potassium and nitrogen. In fact, many horticulturists openly agree that soil testing is one of the most important investments you will make. With the availability of home kits for soil testing, you don’t have to hire a professional to conduct the test as you can do it yourself at a fraction of the cost. By taking the time to determine the acid-to-alkaline pH balance, you will be able to determine what specific plants are able to absorb your fertilizers well and if they are getting the nutrients they require for growing and proliferating.

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  • Most Popular
  • Best Overall
  • Best Budget
  • Buying Guide

  • See also on
    Amazon.co.uk | Amazon.ca

    Most Popular Soil Test Kit

    Luster Leaf 1601

    5/5 Product Rating

    The RapiTest Soil Test is manufactured and distributed by Luster Leaf Products, Inc. This kit is specifically designed to offer a simple, easy to use and highly accurate test that even beginners and homeowners can use.

    It can be conducted on over 450 plants for gardens, homes and yards. It features a device called the color comparators, with one indicator for each of the following: potash, phosphorus, pH and nitrogen. The kit is color coded and comes complete with a color chart. This soil test kit is designed to allow you to grow and enjoy abundant flowers, greener lawns and bigger yield on fruits and vegetables.

    The kit includes 10 individual tests and can be conducted following three simple processes. The charts are also designed to be waterproof and come with complete instructions on how you can adjust your soil condition and proper fertilization.

    • Extremely easy to use
    • Ideal for amateur gardeners
    • Comes with comprehensive instructions in layman’s terms
    • Fast order processing and shipping

    – Anthony Dawson


    See also on
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    Best Overall Soil Test Kit

    Luster Leaf Rapitest

    4.9/5 Product Rating

    This soil tester from Luster Leaf features five easy to use coded testing tubes along with a color comparing chart designed to help you accurately determine the pH balance of your soil. The kit includes 4 test kits for pH balance, 2 for phosphorus, 2 for nitrogen and 2 for potash carded.

    Packaged with easy to understand instructions, color coded design; any amateur gardener can easily understand and interpret the test results without professional assistance. Now you can easily test your soil and look forward to better yield and more lush lawns with this simple and affordable test kit.

    Whether you are planning to grow some turf, plant vegetables or flowers, this is the soil test kit you need to easily determine how you can effectively use your fertilizers to grow your garden.

    Know exactly what your soil needs are to support your plants and vegetables and look forward to better results that will impress your family and friends.

    • Easy to apply
    • Easy to interpret soil sample results to determine pH balance of soil
    • Ideal for home gardeners and those who plan to prepare soil and perform composting
    • Cost effective
    • Accurately pinpoints deficiencies in soil

    – Anthony Dawson


    See also on
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    Best Budget Soil Test Kit

    Environmental Concepts

    4.7/5 Product Rating

    For advanced gardeners and professionals who want to take their planting and gardening prowess to the next level, this soil test kit from Luster Leaf is specifically designed for professional and commercial use.

    The product comes with a sturdy plastic case for maximum protection. It also includes a comprehensive booklet to help you perform the process accurately as well as interpret the results to your best advantage.

    This kit offers a quick, accurate and simple inexpensive alternative to hiring a professional soil tester. Instead of wasting your money with fertilizers that may not be properly absorbed by your plants, you can be sure all the nutrients are maximized and minimize having your money go down the drain.

    • Easily and accurately determines deficiencies in soil
    • Affordable alternative to professional soil testing
    • Generate results in minutes
    • Very useful
    • Very compact and user-friendly

    – Anthony Dawson

    Soil Test Kit Buying Guide

    Both amateurs and those skilled in making a living from the commodities grown on the land benefit from ensuring that the soil in which they grow their plants and crops are fully fortified and contain all of the required elements for growing healthy plants. While some believe that fertilization and weed control are adequate, others understand that testing the soil is important for ensuring that the very best conditions exist for growing healthy plants.

    There are many different soil testing kits available on the market and choosing the best soil tester can leave some wondering where to begin. This guide is prepared to help you to know why soil testing is important, which tests should be conducted, and what to look for when choosing the right soil tester.

    Why Soil Testing Is Important

    Have you ever grown garden plants that appear healthy but have thrown their fruit prior to reaching maturation? This can be frustrating, but there are ways to avoid this happening. There is nothing more disheartening than watching a plant wither away and die, or to fail to produce the lovely blooms or healthy fruit that you have anticipated since planting the seeds in the ground.

    Not all soil is in the optimal condition for growing healthy plants. There are several reasons why soil may not be suitable without conditioning. Some crops delete the nitrogen supply and other important nutrients found within healthy soil. The soil may have been over fertilized, creating an environment in which the plants may grow too fast and become more vulnerable to disease. Soil testing can measure the ph levels in the soil along with a variety of other characteristics that will tell you if the soil needs treatment to bring it into alignment with the types of plants that you intend to grow. It can also help you to determine which plants would thrive in the environment and when it is time to fertilize. The only way that you will be able to distinguish the condition of the soil is through accurate soil testing.

    Soil Traits That Are to Be Tested

    Regular soil testing

    It is recommended, but testing for the right things is vital. One of the most important things that you need to know about your soil is the pH level. The pH levels affect how well certain plants do in a given environment. This is measured in numbers from one to fourteen. For this test, levels under 7 are acidic and above 7, alkaline. When the soil is too acidic it can actually prevent plants from absorbing the nutrients that are found within the soil.

    Conductivity

    It is determined through two measurements tested. These are electrical conductivity also known as EC, which refers to the amount of nutrients that are present within the soil, and TDS which stands for total dissolved solids which measures the amount of fertilizer that exists in the soil. This is how growers determine how much fertilizer is needed.

    Soil temperature

    This is important when sowing certain seeds. Some seeds require specific soil temperature ranges to successfully germinate and emerge into plants. The depth of the measurement taken with regard to the depth that the seeds should be planted is vital. It is important that the soil is tested at consistent depths to get accurate results.

    Different Types of Soil Testers Available

    In addition to a wide variety of brands that are on the market, there is a selection of soil testing types. The differing types of tests include those for measuring pH levels in the soil through the use of a soil pH meter.

    Other meters that are designed to test light and moisture levels are also available. Soil testers may be sold in kits or as individual tests that contain as many as four individual soil testers. It is recommended that you test all of the components of the soil initially, and that at a minimum, the pH levels are tested on a regular basis. If you were to select one test to complete, the pH would be the most important.

    What to look for in soil testers

    If you are unfamiliar with soil testing, the best types of soil testers to begin with are kits that include helpful instructions on their use and care when storing. These tests will also need to be calibrated with the correct solution. Testing kits that include a manual that describes how to properly calibrate the tests will help you to achieve the most accurate results. If tests are not done correctly, the information that you obtain can result in either under fertilizing or over fertilizing the soil. This can interfere with the quality of the plants that are produced.

    For confidence in choosing the most reliable brands, it is worth a few moments of your time to peruse the available online customer reviews prior to purchasing. Consumers who have purchased and used these products describe their personal experiences with them and this can help to give you an idea of which brands will provide you with the best results.

    Conclusion

    Soil testers are important for anyone who wishes to ensure that the soil they will use is ready for the type of plants that are to be grown. By conducting a few simple tests, you will gain the knowledge of what, if anything needs to be done to condition the soil so it is adequate to provide the nurturance of healthy plants. This can mean the difference in plants that will thrive and produce quality flowers, fruits or vegetables, and those that may fail to grow or appear weak and sickly.

    There are four main tests that should be conducted, but if you elect to choose only one, the pH testing is the most important. If the soil is either too acidic or too alkaline, certain plants may not survive in the environment. Prior to purchasing any soil tester, it is recommended that you browse through the many online customer reviews to find out what other people have to say about specific brands. This will help you to have an idea about which brands and types tend to be the most reliable.

    5 Best Soil Testing Kits for pH Acidity, Moisture and Light

    Soil Testing Kit Buying Guide

    Acid, alkaline or neutral soil: does it actually matter?

    This topic is going to cause some debate…

    An overly acidic or alkaline soil pH can mean your garden doesn’t have enough of the nutrients your plants require. Is this a problem? It depends on your gardening personality.

    There are several different types of gardener as I see it:

    Type 1 – tests the soil, improves it if necessary and chooses plants based on their scientific data. Manure is delivered on a tail-gated lorry each year. They grow rather enormous carrots and blue hydrangeas. When asked what type of soil they have reply with ‘Mildly alkaline but nearing neutral in some borders.’

    Type 2 – buys plants they love and hopes for the best. They think plants have managed for thousands of years without interference so they can take their chances now. They like daisies in the lawn. When asked what type of soil they have reply with ‘Brown’.

    Obviously soil pH is going to matter more to a type 1 gardener than a type 2.

    But no matter what camp you sit in, you have to know your soil first.

    What Is Soil pH?

    Soil pH describes the acidic or alkaline nature of your soil. This indicates what kind of nutrients your soil is likely to hold. Nutrients like iron, magnesium, calcium and potassium are important for healthy plant growth. If you want healthy plants it pays to know your pH.

    A pH of 7 means your soil is neutral. At this point soil nutrients are at their best. Anything above 7.0 is alkaline (think chalky) anything lower than 7.0 is acidic.

    Alkaline Soil

    A pH above 7.0 means the soil is alkaline. At this point phosphorous, iron and manganese levels are lowered. This can lead to poor plant growth, but on the plus side it reduces club-root disease in brassicas (greenery such as cabbage). There’s always a bright side.

    Alkaline is the most difficult type of soil to change, so you’re best off choosing plants that like alkaline soil.

    If you desperately want to the change your alkaline soil conditions then you’re in for a struggle with Mother Nature. Use acidifying sulphur agents or buy pine needle compost. Keep digging it in and mulch thickly with ‘organic matter’ (that’s horse/ chicken /farmyard poo to most of us). You’ll need to make these improvements every year because the soil will revert back to its comfort zone.

    Acid Soil

    A pH below 7.0 points to acid soil. That sounds bad but it’s actually beneficial in small amounts. It depends how acidic it is.

    A pH of 3 – 5 is very acidic. There’s going to be a lack of copper, calcium and magnesium plus bacteria can’t rot down plants and organic matter when the pH is below 4.7, so no goodness gets into the soil. Nutrients are used up quickly with no replenishment. It’s a bit like the Ferrero Rocher crisis at Christmas.

    Or perhaps you’ve got an acid pH of 5 – 6.

    That’s not so bad. You’ll be a master of rhododendrons who love acid conditions. You’ll still have some of the issues above but not to such an extent.

    A pH of 6 – 7 is the least acidic and good for growing. Just about everything will thrive in this soil because the nutrients are plentiful. It’s Club Tropicana for worms.

    If your soil is very acidic you can dig in lime. This will help balance out your pH, but you’ll have to keep doing it each year.

    Neutral

    A pH of 7.0 is considered neutral. Plant whatever you like.

    How To Identify Soil pH

    You can send a sample of soil off to places such as the RHS for scientific analysis, but if you’re not that far inclined a simple testing kit will give you a perfectly sufficient read out. If you’re even less inclined here are two DIY methods:

    You’ll need:

    • Soil
    • Baking soda
    • Vinegar

    Alternatively:

    • A mophead or lacecap hydrangea, but not a white one.

    Scoop up a good handful of soil from the growing areas of your garden. Separate this into two cups. Add vinegar to one cup of soil. If it fizzes it’s alkaline.

    Add some water to your other cup of soil so it’s tacky and muddy but not drowned. Add half a cup of baking soda. If it fizzes your soil is acidic.

    No reaction means you’ve got a pH of 6.5 -7.00 and the best type of soil.

    The hydrangea method:

    Hydrangeas are lovely plants. Mophead and lacecap varieties flower all summer and look stunning. Most varieties will bloom blue in acidic soil and bloom pink in alkaline but a white variety will stay white. If you desperately want the blue type then grow your hydrangea in ericaceous compost. This is easily found online or in garden centres. You should also water it with rain because hard tap water can turn blue flowers pink!

    Perhaps the cheapest way to identify your soil pH is by taking a look in your neighbour’s garden. Marvellous camellias and rhododendrons in the ground mean soil is acidic. Stunning clematis, cherry and yew means it’s likely to be alkaline.

    So What Plants Suit?

    Neutral, mildly acid or mildly alkaline soil isn’t going to make much of a difference to your planting strategy, but if your soil is leaning very strongly in one pH direction you’ll save money and time buying a plant to suit it.

    If you have a strong pH, sometimes you can grow many ‘unsuitable’ plants by filling the planting hole with compost and mulching regularly as this maintains a more neutral growing condition. I do this with camellias on my alkaline soil and they’re doing just fine.

    If you’d rather not fight nature here’s a rundown of some easy to grow plants that like a strong pH.

    Acidic

    Alkaline

    Alpine pinks, delphiniums, baby’s breath, carnations, ferns, lilacs, mock orange and spiraea.

    If you currently have plants that just aren’t thriving even with enough water, light and food (be honest now, are you looking after them properly?) then the soil may be to blame. If you have an acid-loving plant listed above with yellowing leaves and stunted growth you probably have alkaline soil. Dig them out and house them in a container of compost. If they improve, then you know the answer.

    You can’t go wrong by digging manure or compost into your soil, no matter what its pH. Organic matter replenishes spent soil. You can’t expect nutrients to last forever, especially the way we rake up leaves and remove all the food plants have made for themselves. Try digging your leaf fall into the earth, if you don’t have leaf fall, invest in some compost and you’ll see you plants improve no matter if it’s acidic or alkaline soil they’re in.

    It’s worth being aware of your soil pH because it can help your plants to thrive. You only need to do this once and then simply choose suitable plants. This will cut down on work, save you money, brighten your outside space and make all the difference to your garden.

    Insect and pest control assortment Dobbies Garden Centre Grovelands

    Back to the overview

    Get in control of pests and insects with pest and insect control products from Dobbies Garden Centre Grovelands in Reading. Pest control is part and parcel of your gardening life, and it’s pretty certain that at some point you’ll need to defend yourself against an attack from six-legged beasties as intent on eating your produce as you are.

    Your Berkshire garden centre is here to help in the war against pests: they’ve got every pest control weapon you could need to tackle outbreaks of nasties from slugs to aphids and mealybugs to spider mites. Bring in pictures or samples and the team will be happy to diagnose your problem and help you tackle it effectively.

    Prevention is better than cure with pest control at Dobbies Garden Centre Grovelands

    Your pest control should start long before you have a problem, though. Stopping the pests getting to your plants in the first place is half the battle, and avoids the damage that can be inflicted as pest numbers build.

    Barriers keep pests off before they even get started. Lightweight horticultural fleece, available off the roll or in handy packets at Dobbies Garden Centre Grovelands here in Reading, is a great pest control for keeping carrot fly off, while insect-proof mesh over the brassica bed excludes pigeons and cabbage white butterflies too.

    If you do suffer an attack of insects

    Inevitably some pests slip through the barriers, so stay vigilant and be ready with the pest control to protect your plants the moment you see signs of trouble.

    Small colonies of aphids are easily squished between thumb and forefinger: but for larger infestations you’ll need a bottle of insecticidal soap from Dobbies Garden Centre Grovelands. It’s derived from plant-based fatty acids so completely organic: spray onto plants in dry weather and repeat as necessary.

    Tackling the dreaded slug with Dobbies Garden Centre Grovelands pest control

    Public enemy no. 1 though needs a special level of pest control. Slugs and snails are the bane of British gardeners, eating up to 40 times their bodyweight in plant material each season.

    Protect individual plants with barriers of grit, wool pellets or copper tape which creates a mild electric charge to zap slugs before they reach your plants. Slug pubs and wildlife-friendly ferrous phosphate slug pellets are also really effective.

    You can also protect entire beds by harnessing the power of Mother Nature. Among the best selling products in the range of biological pest controls at Dobbies Garden Centre Grovelands is a slug-eating nematode you just water onto the ground every six weeks for season-long control. Ask the staff at the garden centre for a demonstration: we guarantee you won’t look back.

    Commercial feature: How to create a herb pyramid

    Dobbies Garden Centres

    What you’ll need

    • 35cm, 20cm and 15cm terracotta pots
    • Horticultural grit
    • Compost
    • Watering can
    • Selection of 9cm pot herb plants
    1. Add compost to your largest pot until it’s virtually full. Firm it down with your hands.
    2. Sit the next pot on the compost and begin to plant herbs around the edge. Use five herbs in the bottom layer. Herbs such as curly leaf parsley, oregano, variegated thyme, golden marjoram and coriander work well. As mint is such a vigorous plant, it’s usually better to grow in a separate pot.
    3. Repeat the process with the middle pot, followed by the one on the top. Use three herbs in the middle layer and one in the top. A great option for the top is rosemary, as it will also flower in the spring.
    4. Add a layer of horticultural grit to the surface of the compost – this will provide a smart finish and deter slugs.
    5. Ensure the pyramid is in a sunny spot for best results and water it gently.

    See how to create a herb pyramid with our step-by-step video at dobbies.com/grow-how
    Dobbies grow howLook out next week for our guide to growing sumptuous strawberries, and for additional tips, guides and ideas in the meantime, visit dobbies.com/grow-how

    Acid soils

    Note Number: AG1182
    Updated: April 2005

    Why worry about acid soils?

    Soil acidity is a natural and induced chemical condition of soils that can:

    • decrease the availability of essential nutrients;
    • increase the impact of toxic elements;
    • decrease plant production and water use;
    • affect essential soil biological functions like nitrogenfixation; and
    • make soil more vulnerable to soil structure decline and erosion.

    The process of soil acidification is a potentially serious land degradation issue. Without treatment, soil acidification will have a major impact on agricultural productivity and sustainable farming systems and acidification can also extend into subsoil layers posing serious problems for plant root development and remedial action.

    In some regions, there has been a drop of one pH unit over the last 20 to 30 years. Already, some farming areas have lost the ability to grow preferred agricultural species such as phalaris and lucerne simply because, without lime, the soil is too acid.

    Understanding soil acidity

    Figure 1: The Causes of Soil Acidity

    Soil acidity occurs naturally in higher rainfall areas and can vary according to the landscape geology, clay mineralogy, soil texture and buffering capacity. Soil acidification is a natural process, accelerated by some agricultural practices (Figure 1).

    When plant material is removed from the paddock, alkalinity is also removed. This increases soil acidity. When grain, pasture and animal products are harvested from a paddock, the soil is left more acid. Hay removal is particularly acidifying because large amounts of product are removed.

    More significantly, soil acidification is most often a result of nitrate leaching. Nitrogen is added to the soil in a number of ways:

    • nitrogen fixed by legume-based plants;
    • as nitrogen based fertilisers;
    • from breakdown of organic matter; and
    • dung and urine.

    Acidification occurs in agricultural soils as a result of the:

    • removal of plant and animal products;
    • leaching of excess nitrate;
    • addition of some nitrogen based fertilisers; and
    • build-up in mostly plant-based organic matter.

    Soil pH

    Figure 2: Relationship between pH measured in Calcium Chloride and Water

    Soil pH is a measure of acidity or alkalinity. A pH of 7 is neutral, above 7 is alkaline and below 7 is acid. Because pH is measured on a logarithimc scale, a pH of 6 is 10 times more acid than a pH of 7. Soil pH can be measured either in water (pHw) por in calcium chloride (pHCa) and the pH will vary depending on the method used. As a general rule, pH measured in calcium chloride is 0.7 of a pH unit lower than pH measured in water (Figure 2). When a laboratory measures your soil’s pH it is important that they specify which method (water or calcium chloride) was used.

    For most acid soils, the most practical management option is to add lime to maintain current soil pH status or increase surface soil pH.

    The acid attack

    Acidity itself is not responsible for restricting plant growth. The associated chemical changes in the soil can restrict the availability of essential plant nutrients (for example, phosphorus, molybdenum) and increase the availability of toxic elements (for example, aluminium, manganese). Essential plant nutrients can also be leached below the rooting zone. Biological processes favourable to plant growth may be affected adversely by acidity.

    Bacterial populations generally prefer a slightly acid environment. However highly acidic soils can inhibit the survival of useful bacteria, for example the rhizobia bacteria that fix nitrogen for legumes. As the soil acidifies, the favorable environment for bacteria, earthworms and many other soil organisms is degraded. Acid soils have a major effect on plant productivity once the soil pHCa falls below 5:

    • pHCa 6.5 – optimum for most plant growth; neutral soil conditions; some trace elements may become unavailable.
    • pHCa 5.5 – balance of major nutrients and trace elements available.
    • pHCa 5.0 – aluminium may become soluble in the soil depending on soil type; phosphorus combines with aluminium and may be less available to plants.
    • pHCa 4.5 – manganese becomes soluble and toxic to plants in some soils; molybdenum is less available; soil bacterial activity slows down; aluminium becomes soluble in toxic quantities.
    • pHCa 4.0 – soil structural damage begins to occur.

    Soil pH will influence both the availability of soil nutrients to plants and how the nutrients react with each other. At a low pH many elements become less available to plants, while others such as iron, aluminum and manganese become toxic to plants and in addition, aluminum, iron and phosphorus combine to form insoluble compounds. In contrast, at high pH levels calcium ties up phosphorus, making it unavailable to plants, and molybdenum becomes toxic in some soils. Boron may also be toxic at high pH levels in some soils.

    The relative availability of 12 essential plant nutrients in well-drained mineral soils in temperate regions in relation to soil pH is shown in Figure 3. A pHCa range between 5 and 6 (between heavy lines) is considered ideal for most plants.

    Understanding soil pH by testing

    Soil pH is one of the most routinely measured soil parameters. It is used as a benchmark to interpret soil chemical processes and governs the availability of many essential or toxic elements for plant growth.

    Soil pH is a common measure of the soil’s acidity or alkalinity because:

    • testing is relatively easy; and
    • field equipment to measure pH is relatively inexpensive.

    Figure 3: Effect of pHca on the availability of plant elements.

    Field test kits are available that use colour to indicate pH levels. The kits are inexpensive, easy to use and will test a lot of samples but should not be relied on for decisions such as rates of lime application. Test kits will only tell you whether your soil is acid or alkaline.

    A number of compact testing meters that can be used out in the paddock are available, most of which are capable of giving accurate results if used correctly. Professional soil analysis is recommended and sending soil samples to a recognised laboratory ensures the most accurate results.

    Testing of both topsoil and subsoil is recommended. When interpreting plant responses based on soil pH, the surface (A horizon) and sub-surface (B horizon) need to be considered.

    The soil pHW is considered to be closer to the pH that the plant roots experience in the soil. But it is subject to large variation within the paddock because of seasonal changes in soil moisture and the ionic concentration of the soil solution that is related to the amount of total salts in the soil.

    Research has shown that seasonal variation of pHW can vary up to 0.6 of a pH unit in any one year. In comparison, the measurements of soil pHCa is less affected by seasons.

    Farmers can take soil samples at different times during the year without affecting the final diagnosis or interpretation.

    Soil pHCa measurements in Australia vary from pHCa 3.6 to pHCa 8 for a range of different soil textures (sandy loams to heavy clays). Soil pHW values lie between pHW 4 and pHW 9.

    Higher pHW values to around 10 may be associated with alkali mineral soils containing sodium carbonates and bicarbonates.

    Useful tips

    • Soil pH is measured in either water or in calcium chloride. When measured in calcium chloride, the result is lower than pH measured in water.
    • The pHW may be higher by 0.6 to 1.2 in low salinity soils and higher by 0.1 to 0.5 in high salinity soils. Research has shown a difference of 0.7 for a wide range of soils.
    • Soil testing will tell you the current acidity status of your paddock. If your soil pHCa is above 5.5 then there is little immediate risk of acidity.
    • Lime can restore productivity in acid soils and should be considered once the pH drops below pHCa 5.0 if sensitive species are to be grown successfully.
    • You are unlikely to get responses to lime if other nutrients are lacking. This should show up in a soil test or plant tissue analysis and should be corrected. Conversely, you may not get a response to some nutrients if the soils are too acid. A holistic balanced approached is necessary.
    • Lime responses are generally seen in the first and second year for cropping systems, but can take up to five years depending on soil type, rainfall and lime quality for permanent pasture systems.
    • It is necessary to re-lime your paddock about every 10 years, depending on the rate of re-acidification.
    • If paddocks with an acidity problem are not limed, the soil pH will continue to fall and settle at pHCa3.8 to 4.2.
    • The amount of lime you need to apply varies according to soil type. Field experiments have shown that up to 5 tonnes a hectare on clay loams and 1.5 tonnes a hectare on sandy soils is needed to increase pH by one unit.
    • Lime moves slowly (0.5 to 1cm per year) through the soil profile via the soil macropore structure. Incorporation into the soil profile, where possible, will assist effective treatment.
    • In permanent pasture situations, spreading the lime on the surface and allowing it to work its way into the soil is acceptable. Surface application is better than no application.

    The following Agnotes may assist landholders with field sampling procedures for soils:

    Agnote AG0375: Sampling soils for growing pastures, field and fodder crops.

    Agnote AG0376: How to sample soils used for flower, fruit, grape and vegetable production.

    Agnote AG0889: Guidelines for sampling soils, fruits, vegetables and grains for residue testing.

    Acknowledgements

    This information note was developed by Carole Hollier and Michael Reed. Rutherglen. April 2005.

    Be Inspired Blog – California

    Posted on: March 20, 2019

    One key element to determining the success of your garden is using the right soil; the vast majority of a plant’s success is directly related to it. Soil, even acidic soil, is a living dynamic organism that is the foundation of life for your plants.

    There is a lot that goes into soil health and the experts at SummerWinds Nursery can help you achieve and maintain a healthy garden through it. They can help you select the best organic soil, choose between organic fertilizer and nitrogen fertilizer and offer many options for organic pesticides. In the meantime, here is some basic information about soil health.

    Understanding Soil Health

    Soil health, also known as soil quality, is defined by the Natural Resources Conservation Service Soils as, “The continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans.” This definition speaks to the importance of managing soils so they are sustainable for future generations. To do this, we need to remember soil contains living organisms; when provided the necessities of life – food, shelter, and water – they perform functions required to produce food and fiber.

    Soil isn’t an inert growing medium, but rather is teaming with billions of bacteria, fungi and other microbes that are the foundation of an elegant symbiotic ecosystem that can be managed to:

    • Provide nutrients for plant growth
    • Absorb and hold rainwater for use during dryer periods
    • Filter and buffer potential pollutants from leaving our fields
    • Serve as a firm foundation for agricultural activities
    • Provide habitat for soil microbes to flourish and diversify to keep the ecosystem running smoothly

    Determining Soil Health

    There are 17 elements considered to be essential for plant growth; nitrogen, phosphorus and potassium are the most important. They are known as primary, or macronutrients, because plants take them from the soil in the largest amounts. Fertilizers that contain all three of these nutrients are labeled ‘complete fertilizers,’ but they hardly encompass everything a healthy garden needs.

    Calcium, magnesium and sulfur, known as secondary nutrients, are also important to many plants. Lesser or micronutrients include boron, copper, iron manganese and zinc. Some plant micronutrients have specific functions, such as cobalt, which isn’t used by most plants, but helps legumes fix nitrogen. Another critical component of your soil is its acid-alkaline balance, or pH reading. All these essentials combined with the proper texture make for healthy soil.

    Acidic soil is often difficult to understand and not everything can grow in it. Keep reading below for more information on this type of soil and how SummerWinds can help you use it effectively in your garden.

    What is Acidic Soil?

    Soil acidity is measured on a scale of 1 to 14, which is the same scale used to measure other types of acid. Everything that ranks below a 7 is understood to be acidic and things that are above is considered to be alkaline. Typically, most garden plants thrive at a pH between 6 and 7.5.

    According to the College of Environmental Science and Forestry, “Soil pH or soil reaction is an indication of the acidity or alkalinity of soil and is measured in pH units. Soil pH is defined as the negative logarithm of the hydrogen ion concentration. The pH scale goes from 0 to 14 with pH 7 as the neutral point. As the amount of hydrogen ions in the soil increases the soil pH decreases thus becoming more acidic. From pH 7 to 0 the soil is increasingly more acidic and from pH 7 to 14 the soil is increasingly more alkaline or basic.”

    According to the Spruce, “The reason a pH between 6 and 7.5 is optimal for garden plants is that between 6 and 7.5, phosphorus in the soil is soluble – meaning that it dissolves in water and is taken up by plant roots. Phosphorus is one of the three macronutrients all plants need (in the NPK ratios you see on packaged fertilizers, phosphorus is the center number) and is responsible for helping the plant bloom and/or set fruit.”

    What Causes Acidic Soil?

    The Spruce also notes that there are three things that cause acidic soil:

    • The first, and most common, is simply that the organic matter and minerals that break down in soil over time are acidic in nature, and make the soil acidic. This is common in pine forests and peat bogs.
    • The second way soil becomes acidic is via leaching due to excessive rainfall or irrigation. Too much water results in key nutrients, such as potassium, magnesium, and calcium, being washed out (leached) from the soil. These elements all prevent soil from being acidic, so when they’re leached out, the pH level if the soil starts to drop, resulting in acidic soil.
    • The third way soil becomes acidic is the use of high-nitrogen synthetic fertilizers. These fertilizers are usually ammonia-based, which increases soil acidity.

    Understanding Plant Hardiness Zones

    According to the United States Departments of Agriculture, the “USDA Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. The map is based on the average annual minimum winter temperature, divided into 10-degree F zones.” to view the map.

    6 Types of Flowers That Thrive in Acidic Soil

    How do you know which flowers to plant in your acidic soil?

    According to SF Gate, “Soil in rainy areas tends to be more acidic than the soil in dryer areas, but many flowering plants favor a lower pH level, which determines soil acidity or alkalinity. The lower the pH, the more acidic the soil. In general, soil with a pH level of 4.6 or less is considered to be too acidic for most plant life.”

    SF Gate put together a helpful list of flowers that thrive in highly acidic soil:

    • 1. Hydrangeas
      These plants grow in U.S. Department of Agriculture zones 4 through 9. Hydrangeas grow into small to medium bushes which produce large flower clusters made of even smaller flowers; the most popular colors of this flower are white, pink, green and blue. If you want to grow a blue bloom, the pH of the soil needs to be between 4.5 and 5.5. These plants do well in partial shade and moist soil.
    • 2. Camellias
      Camellias grow best in partially shaded areas of sun with well-draining soil in zones 6 through 9, depending on the variety. The plant flourishes in mildly acidic soil with a pH of 5.0 to 6.0 and becomes a medium-sized evergreen climbing plant that flowers in the spring.
    • 3. Foxgloves
      Foxgloves are a biennial and perennial plant with small flowers in a “tubelike” shape that open along the stem. These plants come in a variety of colors, including pink, purple, white and yellow. They grow in the late spring and summer, and do best in shady areas in USDA zones 3 through 8. Foxgloves prefer slightly acidic soil with a pH as low as 5.5.
    • 4. Rhododendrons and Azaleas
      Rhododendrons and azaleas bloom to be small to medium-size bushes and typically produce white or pink blooms, although other colors are available. These two plants do best in acidic soils with a pH between 4.5 and 6.0 and are hearty in USDA zones 3 through 9, depending on variety.
    • 5. Zinnias
      According to SF Gate, “Zinnias are small, colorful flowers similar to marigolds. The plants bloom in the summertime and are extremely versatile. They can grow in most of the United States in USDA zones 3 through 10. The plants thrive in acidic soil with a pH as low as 5.5.”
    • 6. Bleeding Hearts
      SF Gate calls the Bleeding Heard plant, “A unique ornamental plant,” as they showcase pink and white flowers shaped like hearts dangling from the stems. “The plant does well in USDA zones 3 through 9 and fares best in partial sun. The plant flourishes in mildly acidic soil with a pH of 5.0 to 6.5.”

    About SummerWinds Nursery: SummerWinds Garden Centers is a leading high-end retailer of garden and nursery products. Headquartered in Boise, Idaho, SummerWinds operates retail nurseries in Silicon Valley, California and the greater Phoenix, Arizona area, making it one of the largest independent retail nursery companies in the nation. SummerWinds appeals to both the serious and casual gardeners, with a broad selection of premium gardening products and a friendly and knowledgeable staff.

    Soil Acidity

    An acid is defined as a substance that tends to release hydrogen ions (H⁺). Conversely, a base is defined as a substance that releases hydroxyl ions (OH⁻). All acids contain hydrogen ions, and the strength of the acid depends upon the degrees of ionization (release of hydrogen ions) of the acid. The more hydrogen ions held by the exchange complex of a soil in relation to the basic ions (Ca, Mg, K) held, the greater the acidity of the soil.

    NOTE: Aluminum (Al) also contributes to soil acidity, but for simplicity, further discussion of soil acidity will be limited to H as the cause of soil acidity.

    Source: IPNI

    Desirable Soil pH for Optimum Crop Production pH Range

    The desirable pH range for optimum plant growth varies among crops. While some crops grow best in the 6.0 to 7.0 range, others grow well under slightly acidic conditions. Soil properties that influence the need for and response to lime vary by region. A knowledge of the soil and the crop is important in managing soil pH for the best crop performance.

    Soils become acidic when basic elements such as calcium, magnesium, sodium and potassium held by soil colloids are replaced by hydrogen ions. Soils formed under conditions of high annual rainfall are more acidic than are soils formed under more arid conditions. Thus, most southeastern soils are inherently more acidic than soils of the Midwest and far West.

    Soils formed under low rainfall conditions tend to be basic with soil pH readings around 7.0. Intensive farming over a number of years with nitrogen fertilizers or manures can result in soil acidification. In the wheat-growing regions of Kansas and Oklahoma, for example, which have soil pH of 5.0 and below, aluminum toxicity in wheat and good response to liming have been documented in recent years.

    Factors Affecting Soil Acidity

    Rainfall contributes to a soil’s acidity. Water (H₂O) combines with carbon dioxide (CO₂) to form a weak acid — carbonic acid (H₂CO₃). The weak acid ionizes, releasing hydrogen (H⁺) and bicarbonate (HCO₃). The released hydrogen ions replace the calcium ions held by soil colloids, causing the soil to become acidic. The displaced calcium (Ca⁺⁺) ions combine with the bicarbonate ions to form calcium bicarbonate, which, being soluble, is leached from the soil. The net effect is increased soil acidity.

    Nitrogen Fertilizers

    Nitrogen levels affect soil pH. Nitrogen sources — fertilizers, manures, legumes — contain or form ammonium. This increases soil acidity unless the plant directly absorbs the ammonium ions. The greater the nitrogen fertilization rate, the greater the soil acidification. As ammonium is converted to nitrate in the soil (nitrification), H ions are released. For each pound of nitrogen as ammonium, it takes approximately 1.8 pounds of pure calcium carbonate to neutralize the residual acidity. Also, the nitrate that is provided or formed can combine with basic cations like calcium, magnesium and potassium and leach from the topsoil into the subsoil. As these bases are removed and replaced by H ions, soils become more acidic.

    Plants

    Legumes like soybeans, alfalfa and clovers tend to take up more cations in proportion to anions. This causes H ions to be released from plant roots to maintain the electrochemical balance within their tissues. The result is a net soil acidification.

    Subsoil Acidity

    Even if the top 6 inches of soil show a pH above 6.0, the subsoil may be extremely acidic. When subsoil pH’s drop below 5.0, aluminum and manganese in the soil become much more soluble, and in some soils may be toxic to plant growth. Cotton and, to some extent, soybeans are examples of crops that are sensitive to highly soluble aluminum levels in the subsoil, and crop yields may be reduced under conditions of low subsoil pH. If you’ve observed areas of stunted plants in your field, take a subsoil sample in these areas. If the soil pH is extremely acidic (below 5.2), lime should be applied early in the fall and turned as deeply as possible.

    Liming Soil Pays

    Correcting soil acidity by the use of lime is the foundation of a good soil fertility program. Lime does more than just correct soil acidity. It also:

    • Supplies essential plant nutrients, Ca and Mg, if dolomitic lime is used

    • Makes other essential nutrients more available

    • Prevents elements such as Mn and Al from being toxic to plant growth.

    Liming Materials

    Liming materials contain calcium and/or magnesium in forms, which when dissolved, will neutralize soil acidity. Not all materials containing calcium and magnesium are capable of reducing soil acidity. For instance, gypsum (CaSO₄) contains Ca in appreciable amounts, but does not reduce soil acidity. Because it hydrolyzes in the soil, gypsum converts to a strong base and a strong acid as shown in the following equation:

    CaSO₄ + 2H₂O = Ca (OH)² + H₂SO₄

    The formed Ca (OH)² and H₂SO₄ neutralize each other, resulting in a neutral soil effect. On the other hand, when calcitic (CaCO₃) or dolomitic lime (Ca Mg (CO₃)²) is added to the soil, it hydrolyzes (dissolves in water) to a strong base and a weak acid.

    CaCO3 + 2H₂O = Ca (OH)² + H₂CO₃

    Calcium hydroxide is a strong base and rapidly ionizes to Ca⁺⁺ and OH⁻ ions. The calcium ions replace absorbed H ions on the soil colloid and thereby neutralize soil acidity. The carbonic acid formed (H₂CO₃) is a weak acid and partially ionizes to H⁺ and CO₂⁻² ions. Therefore, the net effect is that more ca than H ions are released in the soil, and consequently, soil acidity is neutralized.

    Calcitic Limestone

    Ground limestone contains mostly calcium carbonate and generally has less than 1 to 6 percent magnesium. Its neutralizing value depends on its purity and fineness of grinding.

    Dolomitic Limestone

    Ground limestone is a mixture of calcium carbonate and magnesium carbonate. In some states, it must contain at least 6 percent Mg to be classified as dolomitic lime. Its neutralizing effect also depends upon its purity and fineness of grinding.

    Hydrated Lime

    Hydrated lime (Ca (OH)²) is calcium hydroxide, sometimes called slaked or builder’s lime. Hydrated lime is powdery, quick-acting and somewhat unpleasant to handle. The neutralizing value ranges between 120 and 135 compared to pure calcium carbonate. Fifteen hundred pounds of hydrated lime with a neutralizing value of 135 is equivalent to 2,000 pounds of agricultural lime with a neutralizing value of 100.

    Marls

    Marls are deposits of calcium carbonate mixed with clay and sand that are found mostly in the Coastal Plain section of the Eastern states. Their neutralizing value usually ranges from 70 to 90 percent, dependent on the amount of impurities, mostly clay, that they contain. Their usefulness as a liming material depends on their neutralizing value and the cost of processing. They are often plastic and lumpy, and must be dried and pulverized before application to the soil. Marls are usually low in magnesium. Their reaction with the soil is the same as calcitic lime.

    Basic Slag

    Basic slag is a product of the basic open-hearth method of making steel. The calcium contained is in the form of calcium silicate, and reacts with soil acids in a manner similar to ground limestone. Its neutralizing value ranges from 60 to 70, but since basic slag generally has smaller particles than agricultural lime, it tends to change soil pH more rapidly than conventional agricultural lime. It also contains P₂O₅ ranging from 2 to 6 percent and some micronutrients and magnesium.

    Ground Oyster Shells

    Oyster shells and other seashells are largely calcium carbonate. They make a satisfactory liming material when finely ground and have a neutralizing value of 90 to 110. Since they are composed of primarily calcium carbonate, they contain little or no magnesium.

    Fluid Lime

    A liming material commonly referred to as fluid lime generally consists of finely ground limestone suspended in water at a ratio of about 50 percent water to 50 percent limestone. In most instances, producers of fluid lime utilize very finely ground limestone – most of which will pass a 200-mesh screen. Fluid lime is capable of changing soil pH in a relatively short period of time. This is a distinct advantage in situations in which liming has been delayed to just before planting, or in situations in which low soil pH is discovered after a crop is planted. Keep in mind, since fluid lime contains approximately 50 percent water, this means that a farmer applying fluid lime at the rate of 1,000 pounds per acre would be applying only 500 pounds of limestone.

    Pelletized Lime

    Pelletized lime is finely ground agricultural limestone that is pelletized with the aid of clay or synthetic binders to produce pellets in the 5- to 14-mesh range. Usually, about 70 percent of the initial limestone, prior to pelletizing, passes 100- to 200-mesh sieves. It may be spread with conventional spinner fertilizer spreaders, which makes it attractive to use. Unpublished research indicates that pelletized lime should be allowed to react with a good rainfall or irrigation on the soil surface to disperse the pellets before it is mixed with the soil. If rates of 250 to 500 pounds of this liming material are mixed with the soil before the pellet “melts” down, a limited soil volume may be affected by each pellet, and desirable pH adjustment of the plow layer may not be achieved.

    Use of Fluid Lime and Pelletized Lime

    Fluid and pelletized lime are excellent sources of lime to be used under certain circumstances such as: Correction of a low soil pH condition after a crop is planted; A rapid change in soil pH if liming is delayed to just before planting a crop; For maintaining pH in the optimal range for plant growth and yield. However, these two liming materials should not be depended upon to maintain the soil pH during the full crop-growing season if applied at one-fourth of the recommended lime rate.

    Fineness of Grinding is Important in Selecting Liming Materials

    Lime quality is measured by how effectively it neutralizes soil acidity. This is determined largely by its chemical purity and size of particles. The purity of lime is expressed as calcium carbonate equivalent (CCE). This is a measure of how much of the material can react with the soil to neutralize acidity under ideal conditions compared to pure calcium carbonate. Limestone should have a neutralizing value of at least 90 percent. Even if the CCE of lime is satisfactory, it will not neutralize soil acidity unless the limestone is finely ground. In an attempt to arrive at a more accurate lime rating to measure liming material effectiveness, some states’ soil test laboratories have adopted effective calcium carbonate content for rating liming materials. An efficiency rating is arrived at by multiplying the calcium carbonate equivalent times the effective calcium carbonate content, which is based on the fineness of the liming material.

    Efficiency Factors for Liming Materials

    The following example of the “effective neutralizing value” (ENV) calculation, used by the University of Illinois, serves to illustrate the importance of lime particle size in potential soil acidity neutralization. ENV = Total fineness efficiency x (% calcium carbonate equivalent / 100).

    Assume that a liming material has a 96 percent calcium carbonate equivalent. After screening, the liming material is found to have the following particle size distribution:

    +8 mesh = 4% –8 to +30 = 25% –30 to +60 mesh = 26% –60 mesh = 45%

    The total fineness efficiency factor may be calculated as follows for the example material:

    Total Fineness Efficiency for 1st Year = 63.20

    Therefore, the effective calcium carbonate content of ENV = 63.20 x (96/100) = 60.67 for this example of liming material for the first year.

    These calculations enable a grower to determine the shorter- and longer-term value of the liming material being considered for purchase.

    Most mid-Atlantic and southeastern states use the Mehlich I (double acid) solution to extract P, K, Ca, Mg, Mn and Zn. Most Midwestern states use the Bray I solution for extracting P. For K, Mg and Ca, ammonium acetate is used. In regions having calcareous soils, such as the western Corn Belt and Great Plains, the Olsen test is used to extract P.

    Efficiency Factors: Timing, Placement and Frequency of Application

    For crop rotations that include legumes like alfalfa or clovers, lime should be applied to allow enough time for reaction with the soil before the legumes are planted. Ideally, lime should be applied three to six months ahead of seeding the targeted crop. Applications as late as just before planting, with good soil incorporation, can still be beneficial on strongly acidic soils. Some reduction in soil acidity will still occur, although maximum pH increases are not normally reached until about one year after application of typical agricultural limestone.

    Placement

    Placement is just as important as lime quality. Maximum contact with the soil is essential for neutralization of soil acidity. Most common liming materials are only sparingly soluble in water. For example, ammonium nitrate is about 84,000 times more soluble than pure calcium carbonate. Even if lime is properly mixed into the plow layer, it will have little reaction if the soil is dry. Moisture must be available for the lime-soil reaction to occur. Perhaps the best way to incorporate lime or any other material with the plow layer is to use two perpendicular passes of a combination disc, followed by a chisel plow. Deep plowing of lime does not achieve desirable mixing in the upper 6 to 8 inches of soil. However, because the plow or a heavy breaking disc inverts the lime, it can help to distribute the lime in the upper portion of the subsoil. Choice of tillage equipment will depend on the depth at which soil acidity neutralization is most needed. Good horizontal and vertical mixing of the lime provides the best results. In some cropping systems, like established perennial sods or established no-till crop production, mixing lime with the plow layer is not possible. Lime should be incorporated to adjust the pH in the plow layer before the establishment of these cropping systems. Once the desired pH is reached, it can be maintained by surface applications in these no-tillage systems. Surface-applied lime reacts more slowly than lime that is mixed with the soil, and usually only affects pH in the upper 2 to 3 inches of soil. Research at Pennsylvania State University indicated that surface applications of limestone in no-till crop production can begin to influence soil pH below the 2-inch depth after the fourth year, if lime is applied about every third year. Surface liming every third year with 6,000 pounds of lime/A was just as beneficial as annual lime applications of 3,000 pounds/A.

    Frequency

    The more intensive the crop production, the higher the nitrogen fertilizer or manure use, and the greater the crop yields (and nutrient removal), the greater and more frequent the need will be for lime. Soil sampling is the best way to evaluate soil pH levels and the need for lime.

    Excess Alkalinity – Natural and Induced

    Many soils in the semi-arid and arid regions of the United States have a naturally high pH. They may contain significant quantities of “free calcium carbonate.” However, these areas are not the only ones with problems associated with high pH. Irrigation well water may contain significant quantities of calcium and/or magnesium carbonate in certain regions of the United States. In areas of the mid-South for example, some irrigation well water contains in excess of 3 to 5 milliequivalents of bicarbonate per liter and 3 to 5 milliequivalents of calcium. An acre-foot of water or more per year can deliver more than 300 to 600 pounds of calcium and/or magnesium carbonate (lime) per acre. Sprinkler irrigation systems tend to deliver the lime in the water uniformly across the field. If “flood” or furrow irrigation systems are used, much of the lime from the water may precipitate in the upper regions of fields nearest the water delivery inlets and in the water flow path. In effect, the soil is limed by the irrigation water. If the water distribution and delivery are the same over several years, the soil may become alkaline, with soil pH levels rising to 7.0 and above. Soil pH increases may approach 0.2 pH units per year, until equilibrium is reached with atmospheric carbon dioxide levels. Such soil pH increase will occur more rapidly on coarse and medium-textured soils than on clays, which are more highly buffered.

    If the well water contains significantly more sodium compared to calcium or magnesium, there may be a risk of sodium buildup on soils that do not readily leach. This is more often a greater concern in arid regions than in humid regions. Soils with naturally high sodium levels, or those that have received large quantities of sodium bicarbonate through irrigation, may have pH levels as great as 8.5 or higher. Theoretically, if sodium is not a factor, even if large quantities of calcium or magnesium carbonate are applied, the soil pH will not exceed 8.2 to 8.3. At pH 8.2, the soil carbonate reaches an equilibrium with the carbon dioxide level in the atmosphere. If irrigation water is suspected or known to deliver significant amounts of lime salts and/or soluble salts, soil samples should be collected more frequently to better monitor soil pH, salinity and cation balance. Irrigation water quality should also be periodically monitored.

    Correction of Excess Alkalinity by Soil Acidulation

    Elemental sulfur may be used to acidify alkaline soil to the desirable pH range. It may also be used to maintain pH in the desirable range, on soils that tend to become alkaline with management. When elemental sulfur is applied to soil, it combines with oxygen and water to form sulfuric acid. This oxidation of sulfur is brought about by certain microorganisms, and it may take from three to six weeks or longer, depending on the soil conditions. The finer the sulfur is ground, the more rapid the conversion to sulfate and dilute sulfuric acid. The rate of decrease in pH with elemental sulfur may be similar to the rate of pH increase brought about by liming. The more free calcium carbonate present and the more buffered the soil, the longer it will take to acidify the soil. More sulfur will also be needed on soils with free carbonates present. Aluminum sulfate is another amendment often used in ornamental horticulture to acidify soil in plant beds. However, more of it is needed to produce the same acidification as elemental sulfur, even though it offers the advantage of a faster reaction. Compared to elemental sulfur, the rate may need to be two to seven times greater. Little of this amendment is used in commercial agriculture.

    NOTE: If free carbonates are present, higher rates than those shown will be required. Reference: “Western Fertilizer Handbook,” eighth edition. California Fertilizer Association

    Procedures

    As with soil testing, an important phase of plant analysis is sample collection. Plant composition varies with age, the portion of the plant sampled, the condition of the plant, the variety, the weather and other factors. Therefore, it is necessary to follow proven sampling instructions. Most laboratories provide instruction sheets for sampling various crops, plus information sheets and directions for preparing and submitting samples. It is usually suggested that samples from both good and problem areas be submitted for comparison when diagnosis is the goal. Because experience and knowledge are vital in sampling plants correctly, agricultural advisors or consultants often do the job.

    The Four Basic Steps in Plant Analysis

    • Sampling

    • Sample Preparation

    • Laboratory analysis

    • Interpretation

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