Soil Testing Based on Mehlich III Extraction Methods

Soil testing, wrote Jerry Brunetti in 2009, is the foundation for the actions you take to add fertility to your soil:

I’ve always been a fan of foliar nutrition, especially on forages. However, I don’t advocate the application of foliar fertilizers as a replacement for sound agronomic practices involving comprehensive soil analysis (including multiple trace elements), tissue testing, and an evaluation of the soil ecology.

A soil test can be quite easy to interpret and recommendations can just as easily be made based on the results of the test. Since many articles on soil fertility have been written for Acres U.S.A., this article will provide the reader with an “ideal” test based upon a Mehlich III Extraction.

Forage tests generally determine whether or not you are on target with adequate feeding of the crop and are becoming considerably more revealing than in the past. This is especially true in the measurement of total digestibility and fiber digestibility, protein quality, and the various fractions of energy such as sugars, starches, digestible NDF, etc.

soil test

Relative to measuring biology, I like to poke around in the soil and dung to observe which organisms are present. One of my favorite instruments is a soil penetrometer, which measures soil compaction by disclosing the pounds per square inch (psi) every several inches of depth in the soil. When exceeding 200 psi, your ground is tightening up, which means it’s becoming less aerobic and thus more anaerobic. Like livestock and humans, soil ecosystems need free oxygen in order to breathe. A lack of pore space indicates a lack of oxygen, which results in the disappearance of aerobic life forms. In anaerobic soils, nitrate (NO3-) is denitrified into nitrite (NO2-), nitric oxide (NO), nitrous oxide (N2O) and nitrogen (N2). This is a wasteful loss of the raw material that creates plant proteins.

Adequate oxygen creates adequate aerobic organisms, which exhale carbon dioxide (CO2) gas at 3,000-4,000 ppm in the soil atmosphere. CO2 is absorbed by the plant stomata to combine with water (H2O) and sunlight inside the chloroplast to create plant sugars (CHO). Granulated soil, two to three feet deep, is ideal because it allows plant roots to burrow into the subsoil, which weatherproofs the crop from both excess flooding and drought.

If the soil is compacted after soil testing, do what the golf course industry regularly does — aerate! Subsoiling a couple of inches below the hardpan or plowpan when the soil is moist (not dry, not waterlogged) can perform wonders in allowing root systems to expand. Additionally, an aerification appliance such as the Aeraway is extremely helpful in maintaining the aerobic zone in the top 6 to 8 inches. Cattle are heavy animals, and unless you are a mob grazer and won’t return the herd to paddocks for a number of months, they will compact soils quite substantially.

While we’re on the subject of biology, how many of you farming folk who have livestock would consider yourselves “manurologists,” especially on dung from large livestock? The cowpie is its own eco-system, harboring wonderful livestock friends that not only help control face, horn, stable and house flies, but also consist of dung decomposers that eliminate the patty as a future habitat for parasites. A single dung pat may contain more than 1,000 insects, most of them beneficial if you have a pesticide-free, parasiticide-free farm.

Mites, spiders, parasitoid wasps, and predator beetles such as rove, ground and carcinops, prey on livestock pests’ eggs, larvae and pupae, while earthworms, dung beetles and eventually ants consume and bury the pat. Dung beetles have shown to reduce nematodes (parasite) larvae by as much as 90 percent and hornfly larvae by 95 percent! There are roughly a dozen important species of dung beetles in the United States that aggressively attack manure so that it doesn’t smother the forages. Dung beetles recycle nitrogen, aerate the soil, and reduce 90 percent of the pasture manure in one week. Millions of acres of pasture are lost annually in the United States due to a lack of manure decomposers. There are virtually 1.5 to 2 million species of soil microorganisms, yet fewer than 5 percent have been identified, and it’s still unknown how many types dwell in the guts of the larger life forms such as beetles, springtails, mites, earthworms, etc.

Leonardo da Vinci was right in the 16th century when he said we know more about the movements of celestial bodies than we know about soil life. Little has changed in 500 years. Earthworms (Lumbricus terrestris) at a count of only 25 worms per square foot and a spade deep would provide about one million worms per acre, which in turn would excrete 62,000 pounds of worm castings per acre per year. While aerating and tilling the soil they are capable of burrowing eight feet deep. Worm castings are not only rich in nitrogen, phosphorus, potassium, calcium, magnesium and micro-nutrients, but are also rich in microbes and microbe stimulants. What’s best about worm manure is that the worms produce a product that isn’t phytotoxic, i.e., too high in salts, ammonia, nitrite, etc. Therefore, by incorporating vermicompost, either by making your own or by purchasing it, you’ll supply the crème de la crème of a compost tea.

Nutritious Compost After Soil Testing

Consider the following “soup mix.” Start by brewing a tea using high-quality compost or vermicompost. Then “spike” a 40-50 gallon finished stock solution with the following ingredients and spray it on paddocks approximately ten days following a grazing or cutting:

  • 2 gallons fish emulsion
  • 1 quart seaweed extract
  • 5 pounds dextrose sugar
  • 1 quart humic acid extract
  • 5 pounds Epsom salts
  • 4 oz boric acid
  • 2 gallons calcium nitrate (not for organic use)
  • 1 quart 85 percent phosphoric acid (not for organic use)
  • 1 pint of “Fusion,” a fulvic extract with trace elements
  • Wetting agent as per label

In order to meet the optimum levels you want to accumulate in the plant tissue, based on the tissue test results, add small amounts (e.g., 1 ounce) of copper, zinc, manganese, iron, cobalt and/or molybdenum. If mixing Epsom salts and/or calcium nitrate with phosphoric acid, please know that these are incompatible cation/anionic ingredients and can only be blended together if you use a catalyst such as Fusion, a remarkable, humic/ fulvic extraction containing fulvic acid and approximately several dozen trace elements. It performs like a catalyst in allowing incompatible anion and cations to be mixed without a reaction. It also acts as a chelating agent, a biostimulant and is a source of micronutrients. It has a pH of 2.5-3.0, so it will help adjust the tank mix pH to below pH 6, which is preferred in order to effect optimum absorption by plant stomata. If you are organically certified, the use of calcium nitrate and phosphoric acid are prohibited.

Shop around for micronized calcium and phosphate mineral sources, ideally below 5 microns, which approximates the diameter of the stomata opening. Spray when temperatures are below 80°F, again to increase absorption into the plant stomata. This soup readily benefits the soil ecology as well as the plant tissue. Monitor the progress of this application by getting a comprehensive forage analysis. On site, one can do relative hand meter measurements, using tools such as a brix refractomer, plant sap pH test, and plant-sap nitrogen and plant-sap potassium. Supposedly, plant sap pH should reflect ideal soil and saliva pH — about 6.4. Lower than 6.4 indicates a fungal susceptibility, and higher than 6.4 indicates a susceptibility to insects. Note: the brix refractomer is a relative tool. For example, even though a “perfect world” brix of greater than 12 is the target, testing for brix after several days of cloudy weather will give you a reading substantially below what one would get after several days of sunshine. Measuring for brix late in the afternoon will yield higher readings than in the morning, for the simple reason that photosynthesis has been occurring for a longer period of time. Thus, to really know how you are progressing, measure a treated plot against a control plot on the same soil at the same time.

Of course, this applies to measurements of plant-sap potassium and plant-sap nitrogen as well. Ultimately, the results will be determined by the old adage, “The proof of the pudding is in the eating.” Since livestock don’t eat soil as a primary feedstock, have your forages thoroughly analyzed. Then watch your livestock. Are lactation and growth improving? Do the animals come in heat and settle more successfully? Are the young stocks thriftier? Is the herd or flock more immuno-competent, i.e., less susceptibility to mastitis, respiratory challenges, parasite opportunism, etc.? Foliar soup mixes work as part of a “systems approach” to farm productivity, health and performance. In other words, they appear to give the farmer the biggest return on their investment when soils are recognized as the foundation of a profitable farm, including soil fertility (minerals), soil ecology (biology) and soil structure/tilth, all of which influence one another. The results from applying a foliar soup mix are especially dramatic when the extremes of weather pay a visit upon the landscape, namely drought and heat, or conversely, cold and wet spells. One thing for sure, we don’t seem to have “climate” anymore — just vagaries of the weather.

We’ve also witnessed dramatic improvements on golf courses, a habitat where plant stress is at an extreme due to the fact that a monoculture is grown upon 90 percent sand and is force-fed nitrogen along with heavy applications of herbicides, insecticides and fungicides. Even in this stressful environment, we’ve discovered that disease and insect pressure are reduced due to a boost in the biological factors associated with microbes, microbial exudates, auxins, cytokinins, hormones and enzymes, which interrupt disease processes. Foliar soup mixes contribute nutritionally and help build plant immunity, which results in a decrease in pesticide use so there’s less interference with enzyme systems necessary for plants to synthesize complete proteins and carbohydrates.

Plants rich in complete proteins and carbohydrates are less than optimum substrates for insects and diseases because these primitive organisms produce unsophisticated digestive enzymes capable of breaking down simple “funny” proteins such as nitrate, free amino acids, NPN (vs. complete proteins) and simple sugars rather than polysaccharides, starches and pectins. So, to stay healthy, eat nutrient-dense foods (minerals), maintain optimum digestion (soil micro-flora), and eat your soup!

By Jerry Brunetti. This article first published in the December 2008 issue of Acres U.S.A. magazine. For more information, order from his collection of books and audio presentations.

Soil Testing: The Need for Total Testing

By Hugh Lovel

What many farmers probably don’t know about soil testing is that most soil tests only tell us what is soluble in the soil. They do not tell us what is actually there in the soil, no matter what fertilizer salesmen might like to imply. To find out what is actually there requires a total acid digest similar to what is used for plant tissue analysis. Mining labs run these total acid di­gests on ore samples which are crushed, ground and extracted with concentrated nitric and hydrochloric acid solutions, but a mining assay does not determine total carbon, nitrogen and sulfur as a plant tissue analysis would. These ele­ments need a separate procedure essen­tial for evaluating soil humic reserves.

Most soil tests measure total carbon, which then is multiplied by 1.72 to calcu­late soil organic matter. This assumes that most of the carbon in the soil is humus of one form or another. While this may or may not be true, determining the car­bon to nitrogen, nitrogen to sulfur, and nitrogen to phosphorus ratios is a good guide for evaluating organic matter, and this requires testing total nitrogen, sulfur and phosphorus as well as carbon.

Klaas Martens: Soil, Testing & Fertility from the 2009 Eco-Ag Conference & Trade Show. Listen in as the popular agronomist and successful organic farmer teaches his methods for managing soil testing, data and inputs.

While carbon in almost any form is a benefit to the soil, it helps enormously if it is accompanied by the right ratios of ni­trogen, sulfur and phosphorus. Though these ratios are not set in stone, a target for carbon to nitrogen is 10:1, for nitro­gen to sulfur is 5.5:1 and for nitrogen to phosphorus is 4:1. This works out to an ideal carbon to sulfur ratio of 55:1, and a carbon to phosphorus ratio of 40:1. Because soil biology is very adjustable these targets are not exact, but achieving them in soil total tests is a good indica­tion of humus reserves that will supply the required amounts of amino acids, sulfates and phosphates whenever the soil food web draws on them.

Total soil testing is key to understanding your soils’ needs.

Humus as Vague Science

Humus formation and utilization is a fuzzy subject that has long been poorly understood. Humification may result from long-term geological processes as with the formation of peat, brown coal and leonardite. But humification can also result from humus-forming activ­ity by mycorrhizal fungi, actinomycetes or any microbial species that can add to or withdraw, somewhat like bees stor­ing honey in the hive from the soil’s storehouse of humic acids. The pre­cise carbon structures of humic acids are enormously difficult to characterize, which means carbon structures end up classified as humic acids whenever they are too large to pass through bacterial cell walls. This pretty much limits humic acids to consumption by fungi, actino­mycetes or protozoa. This vague but use­ful rule draws the dividing line between humic and fulvic acids at somewhere around 2,000 atomic weight units — above is humic acid, and below is fulvic.

It is not much easier to determine the precise structures of fulvic acids. Though fulvic acids can also be extract­ed from peat, brown coal or leonardite, generally fulvic acids are low molecular weight residues from the breakdown of plant and animal wastes. However, much of the carbon chemistry that plants give off around their roots as root exudates could be classified as fulvic acids based on molecular weight. This low molecu­lar weight fulvic chemistry is very ver­satile and may be taken up by plants, consumed by soil bacteria, or used by humus building microorganisms to as­semble stable, high molecular weight humic acids.

Many of these humus-forming mi­crobes form symbiotic relationships with crop roots and capitalize on the fact that virtually all plants that are growing well also give off some of their sap as an energy-rich bonanza of root exudates. When photosynthesis is abundant these microbes convert surplus root exudates into humic acids and store them in the soil as clay/humus complexes. Then when there is rain or photosynthetic conditions are not ideal they tap into these stores, much like bees do in the hive. This evens out plant and soil food ­web interactions and keeps things going on a fairly even keel.

Bruce Tainio: Amending Soil Microbial Life, from the 2005 Eco-Ag Conference & Trade Show. (1 hour, 2 minutes) Listen in as the popular agronomist explains how to feed the microbial life in your soil, and develop optimal microbial biodiversity.

Where we really see the benefits of this plant/microbe/humus interaction is where we see root exudate overlap, which will be dealt with later. The important bit here is the organisms that consume humic acids also store them as clay/humus complexes. This is a good reason to use 10 percent soil in making compost to ensure adequate soil surfaces for humus complexes to form. The large molecular weight carbon compounds in the resulting clay/humus complexes will incorporate amino acids, sulfates and phosphates along with silicates and vari­ous cations. Only a small portion of these materials show up on soluble soil tests even though they are available to the mycorrhi­zae, actinomycetes and/or protozoa.

Charcoal & Fossil Humates

Carbon is the basis of life, and in al­most any form carbon benefits the soil by attracting life. Biochar is a very ben­eficial carbon source. But just because something is a carbon source does not mean it has sufficient other elements as­sociated with it. The process of making biochar pretty much guarantees that most of the nitrogen, sulfur and phosphorus are driven off; and since these elements are anions, the char that results — while bio-active — will have a high pH because it will still contain most of its original cal­cium, magnesium, potassium and silicon.

Andre Leu, Soil Carbon, from the 2007 Eco-Ag Conference & Trade Show. (53 minutes, 44 seconds). Listen in as Leu, the director of Regeneration International, teaches how to store and repurpose carbon in your soil.

Fossil humates, such as are mined or extracted from brown coal or leonardite, also tend to be deficient in nitrogen, sulfur and phosphorus. Even composts, which tend to be better balanced, may be deficient in certain elements. Chars, fos­sil humates and composts will increase soil life, but will that soil life scavenge the soil for such things as nitrogen, sulfur and phosphorus and tie them up so they aren’t soluble? We only need small amounts to be soluble on a steady basis.

If we want to achieve the best results we should test and adjust our ratios of carbon to nitrogen, nitrogen to sulfur and nitrogen to phosphorus, not only in our soils but also in the chars, humates or composts we apply — and this requires total testing. The significance of these ratios is huge in developing a long-range plan for thriving, robust growth, efficient pho­tosynthesis and biological nitrogen fixation without resort to nitrogen fertilizers.

Just suppose the ratio of C to N in the soil reserve is 15:1 or even 20:1 and there’s not enough amino acid nitrogen in the soil’s humus reserve. In cloudy weather when photosynthesis is reduced, root exudation and nitrogen fixation are low and the microbial symbiosis with crop roots mines the humus flywheel — then it comes up short in amino acids.

Or suppose the N:S or N:P ratios don’t deliver enough S or P. Will there be enough free in the soil or will the plant come up short? Deficiencies may also include silicon or boron, or any macro- or micronutrients that might be stored in the soil’s clay/ humus complexes. What can the soil’s humus flywheel deliver? Total tests are our best clue.

Keep in mind that we do not want more than a steady trickle of soluble nutrients. For the most part we want our nutrients to be insoluble but available. We should also keep in mind Liebig’s law of the minimum. The great 19th century chemist, Justus von Liebig, pointed out that plants can only grow to the extent of their most deficient element, and it won’t matter how much other stuff they have. This implies that whenever there is a shortage of something in the soil’s humus flywheel, the plant may have to slow down and limp along.

Building N, S & P

Truly amino acids are of first importance for protein de­velopment, but as long as nitrogen fixation supplies a steady stream of amino acids from the microbial symbiosis around crop roots there is no other element closer to hand in greater abundance than nitrogen.

A more urgent deficiency to remedy is sulfur. Sulfur works at surfaces and boundaries making things accessible. As such it is the catalyst for most of plant and soil chemistry. For example, sulfur is what peels the sticky, miserly magnesium loose from its bonding sites in the soil. Without sufficient sulfur the plant may not take up enough magnesium even if it is abundant in the soil. This deprives the plant of sufficient chlorophyll to make efficient use of sunshine, and then there is a shortage of sugary root exudates to feed nitrogen fixation — which requires 10 units of sugar to produce one amino acid. Considering how common magnesium deficiency is in plants growing on magnesium-rich soils, we shouldn’t ignore sulfur deficiencies in the soil reserves. Many soils are abundant with magnesium, but without the 55:1 carbon to sulfur ratio needed for optimum growth, plants can easily be magnesium deficient, poor in photosynthesis — and when they don’t make enough sugar they won’t have good nitrogen fixation.

One can amend sulfur in the soil in various ways. With chars or raw humates, both of which are deficient in nitrogen and sulfur, small amounts of ammonium sulfate (30 to 80 pounds per acre depending on the case) can be helpful. But keep in mind this is a soluble chemical and only so much can be absorbed by the soil’s carbon complexes and the microbial life they support.

Potassium sulfate might also be of use, but total soil testing often indicates an abundance of total potassium and more in soluble form interferes with magne­sium uptake, which usually is counter­productive. Gypsum (calcium sulfate) is most commonly used for corrections, though only about 50 ppm of sulfur (0.4 to 0.6 tons per acre) can be absorbed by the soil in one application.

The problem here is sulfate tends to leach if there’s too much. That might be good if all it carried with it was magnesium as most soils are high in magnesium. But, what if the sulfate carries copper, zinc, manganese or even potassium along with it? Can we afford such losses?

If we try to keep soluble sulfur topped up at 50 ppm (Morgan test) by using gyp­sum mixed with compost or raw humates, gypsum will probably work beautifully and not acidify the soil. It may take a few years to build sulfur levels into the soil totals, but patience is a virtue. However, when the soil pH is already 7.0 or above, elemental sulfur becomes the input of choice. Elemental sulfur pulls oxygen out of the atmosphere as it oxidizes to sulfate and this lowers pH — which for alkaline soils is desirable. Again, try to keep the soluble sulfur level around 50 ppm and gradually build this element into the soil reserves as humic reactions or interactions progress.

Visual Signs

Sometimes we can see a field that had water standing in a streak, puddle or blanket for a day or two, which leached some of the sulfur and left a meander­ing, light-color streak or area where the water was. Often such events are repeat­ed, which can make the area of leaching stand out rather clearly. This is sulfur deficiency, which leads to magnesium deficiency in plant growth on what is probably a high mag soil — which would explain not draining fast enough in the first place. Usually on such soils the calcium leaches leaving the magnesium behind. Fixing such problems takes care­ful applications to the deficient area rather than just making a simple recom­mendation for an entire field. It may be possible to remedy such a deficiency by eye by following the lighter colored area with one or more sulfur applications — most likely gypsum — along with compost, fossil humates or biochar.

Soil expert and author William McKibben, The Art of Balancing Soil Nutrients, from the 2009 Eco-Ag Conference & Trade Show. (1 hour, 8 minutes). Listen in as McKibben talks about the steps you can take after you receive your soil test results to help balance your soil.

Phosphorus may also be deficient, though sometimes total phosphate is surprisingly high without sufficient phosphorus availability. If a total test shows the N:P ratio is too high, add enough rock phosphate to compensate for the deficiency and apply this with compost, raw humates or char inputs. As with sulfur, calculate the amounts once the inputs are spread and don’t go overboard. Adding too much can be like having a soup with too much salt in it.

Keep in mind it is not rare for total tests to show 10 to 100 times as much total P as shows up on soluble tests. Al­though sulfur deficiency limits phos­phorus availability, the key deficiency that often must be remedied to make phosphorus available from soil totals is copper. Phosphorus is useless without copper. Though 2 ppm soluble copper is generally considered adequate, 5 ppm gives more margin and 10 is not harm­ful unless the soil is extremely light with poor humus reserves.

Zinc deficiency can also keep phos­phorus tied up, and a 10:1 phosphorus to zinc ratio is a desirable target in total tests. Total tests of rock phosphates gen­erally show the desired amount of zinc. Usually trace mineral deficiencies such as copper and zinc show up most clearly in winter where these elements work 1/100th less efficiently at 30 or 40°F as they do at 70 or 80°F. The signs of these deficiencies are quite obvious in winter, and if the deficiencies are remedied, growth in cool periods of spring or au­tumn will be much better.

Silicon & Boron

Even though silicon is secondary in importance to sulfur, silicon accounts for all transport in plants. It is the basis of capillary action. As a co-factor, boron works with silicon to provide sap pres­sure and often is found in appropriate amounts in siliceous rock formations. Boron has an affinity for silicon in the capillary linings where borate molecules take the place of silicate molecules. How­ever, boron forms three electron bonds where silicon forms four. Boron’s in­ability to form the fourth bond creates a hunger in the surrounding silicate mol­ecules, which causes them to draw water and electrolytes from the roots through the capillary system to the transpiration sites in the canopy. Without sufficient boron, plants with high boron require­ments like legumes, crucifers, vines, etc., will have too little sap pressure to feed their canopy. Then they may wilt at mid-day or not have enough root exudation at night. Where plants have high brix in the early morning, boron is deficient.

Lest we forget, however, the key role of sulfur is in the soil biology around plant roots where sulfates and sulfur-containing amino acids interact with the surfaces of soil particles, most of which are siliceous. Actinomycetes and mycor­rhizal fungi in particular need sulfur to peel silicon and boron away from the surfaces of clay and sand particles in the soil. This is a gradual process because it only works at surfaces. It is the nitrogen to sulfur ratio in soil total tests that lets us know whether the soil food web can do an adequate job of silicon and boron ac­cess — and this makes a huge difference with how well alfalfa, tomatoes, grapes, wheat or other crops can transport things.

Soil consultant Noel Garcia, with Texas Plant & Soil Lab, speaks at the 2014 Eco-Ag Conference & Trade Show, on the Critical Growth Stages for Optimum Production. (1 hour, 15 minutes.) Listen in as he teaches a class on how to monitor plants for stress, and mineral and nutrition deficiencies.

Most importantly, since photosyn­thesis is hugely dependent upon the ef­ficiency of transport, silicon and boron are essential for efficient photosynthesis. Energy has to travel in chemical form from the chloroplasts, which capture sunlight, to where sugars are made. Also any newly made sugars have to get out of the way of the next sugars being made, and so forth. Anything that slows down transport slows down photosynthesis and will ultimately slow down the nitro­gen fixation that chlorophyll formation depends on.

Sugars & Nitrogen Fixation

Usually sugar is the most limiting factor in nitrogen fixation. This shows up in root exudate overlap. Where garlic, ginger, corn, beans, bananas, etc., double their root density in the soil and have root exudate overlap between plants, they grow more vigorously.

Ever notice where corn is planted too thickly so that five or six seeds sprout in just a few inches? Always the corn sprouts in the middle grow fastest. Later if the corn isn’t thinned there may be competition for nutrients and moisture; but if nutrient and moisture competition was all that was going on the middle corn seedlings wouldn’t be the most robust.

Native Americans used to plant corn — without fertilizer — as a soil-build­ing crop by planting their seeds in tri­angle shaped groups or hills to maximize root exudation, nitrogen fixation, and amino acid uptake. They grew big, tall, long-season corns that built carbon into their soils. In some cases they bundled the stover for winter fuel, which they burned, sprinkling the ashes back on their fields. They did this for hundreds and even thousands of years without recourse to nitrogen fertilizers. In terms of efficiency, agriculture took some giant steps backward in the 20th century.

If we had corn planters that perfectly singulated seed and we could plant with double drills that alternated seeds from left and right drills with 10-inch spacing in each drill and 5 inches in between drills, the seeds would come up in a zig­zag pattern that maximizes root exudate overlap in high population corn plant­ings. This would minimize the need for nitrogen fertilizers.

Soil Testing: An Eye-Opener

As an agricultural consultant in far northern Queensland, Australia, I grew $2,000-$3,000 of culinary ginger in my garden as well as an aloe vera nursery without nitrogen fertilizers. Both were high-silicon crops. At nearby Mt. Garnet we had a diatomaceous earth mine that sold diatomaceous earth (DE) at $300/ton — somewhat pricey, but an excellent silicon fertilizer. When I sprinkled this DE on my ginger it grew beautifully and was twice as robust wherever I spilled a liberal amount. The same was true for my aloe vera. What was clear was that nitrogen fixation and amino acid uptake by both ginger and aloe was far more abundant with high-silicon availability. On a nearby banana farm using the same diatomaceous earth at a rate of 1 ton per hectare (2.5 acres) there were 1.28 more new leaves per month, a sure sign of quality nitrogen availability and robust growth. This meant silicon was a huge influence in nitrogen fixation.

Neal Kinsey, Using Soil Analysis to Grow Crops, from the 2005 Eco-Ag Conference & Trade Show. (50 minutes, 12 seconds). Listen in as agronomist Neal Kinsey, the author of Hands-On Agronomy, teaches about how to test your soils, and use that data, to increase crop yield and decrease weed pressures.

One of the most common problems is too much soluble nitrogen at any given time. A little nitrogen on a steady basis is good, but it is easy to go overboard. Nitrogen availability is a double-edged sword because too much soluble N leads to the nitrification of amino acids, which strips silicon and boron from the soil while shutting down nitrogen fixation. The result is insufficient transport in following crops. We have to be observant and intelligent in our management of soil nitrogen, as ignorance is hardly bliss.

Grasses usually are the best silicon accumulators, which makes maintain­ing them in our soil cover along with legumes a good idea. Bare soil is always a dead loss and a sure way to ensure sili­con and boron leaching — which easily results from too much cultivation, and this welcomes weeds. Weeds love soluble nutrients, which is one of the reasons we don’t want soluble nutrients. What we want is insoluble but available nutrients, and we want to get all our nitrogen from the air where it is abundant.

My target on pastures is to keep sol­uble silicon levels above 80 ppm with totals above 1,000 ppm — not so hard without nitrogen fertilizer abuse. For tomatoes I like 100 ppm soluble silicon which is more difficult; and for cher­ries — a really silicon-sensitive crop — I aim for 120 ppm. This really takes good management though it pays off hand­somely. Hopefully American soil labo­ratories will take total soil testing on board like my Australian lab, Environmental Analysis Laboratories (EAL).

Though growers can send samples to EAL, I’d prefer a quicker, more respon­sive domestic approach. So far Texas Plant and Soil Lab in Edinburg, Texas, and Midwest Laboratories in Omaha, Nebraska, have indicated interest. I’m not sure how they do with the Mehlich III analysis, my preference, but I’d like to think they can perform adequate total soil testing including totals for C, N and S.

This article was published in the April 2013 issue of Acres U.S.A. magazine.

How To Select Your Soil Lab

By Susan Shaner

Soil lab selection: How does anyone choose the right laboratory? Aren’t they all the same? Should you send a sample to several different labs and average the results? How do you get the samples to a lab and what is the turnaround time? Some homework needs to be done here.

These are all questions that I hear on almost a daily basis. All labs are not the same. This does not mean that one laboratory is better than another. They all provide a different “menu” of services. It is important to find a lab that provides all of the services that you require. Are you just looking for a soil analysis, or do you also need an irrigation water test or tissue analysis?

Laboratories can also choose from a number of methods or “recipes” to obtain results. Which method would be best for your soil type or crop? “Presentation” of results can also vary greatly from one laboratory to another. It is important that you can read the report and make use of the information it provides. These are all questions that you should consider before choosing a laboratory.

Menu of Services

Packages with various soil parameters are usually available, plus some a la carte choices. This will vary greatly from one laboratory to another. I think we all agree now that there is a lot more to soil than pH. Therefore, look at what is included in the soil package you are requesting.

soil sample

Important parameters include pH, organic matter, exchange capacity and base saturation. Also important are the major elements calcium, magnesium, potassium, sodium and phosphorus.

Important minor elements include sulfur, boron, iron, manganese, copper, zinc and aluminum. A complete soil analysis including all of these parameters may cost a little more. More information will provide better insight into your fertility situation. If you base your decision on cost alone, you will probably get what you pay for. An inexpensive analysis may only include pH, phosphorus and potassium.


Methodology is the most confusing area when comparing laboratories. There are several different methods for almost every parameter on a soil analysis. Laboratories choose methods that are best suited for the geographical area that they service. Most labs will offer different methods upon request to accommodate most customers; you will have to know what to request first.

Sending the same sample to several labs for comparison will be quite confusing unless you do your homework to determine what methods are used. I have talked with several customers after they have submitted the same sample to different labs without understanding the differences.

They have been very unhappy and disappointed with the outcome. Let’s look at a good example of different methods — for example, phosphorus. There are nine phosphorus test methods that I am aware of. All of these methods were run on a specific soil sample and produced results anywhere from 10.5 to 656 ppm. If you know how to interpret the results for each of these tests, you should come up with the same recommendation. If you do not have the correct threshold levels for the method provided, you could make a big mistake in interpretation.

Presentation of Data

What units of measure do you feel comfortable with? Do you prefer graphic results, high and low distinctions or an actual value found?

Soil reports come in all shapes and sizes. Some reports are very colorful and show your results in a graphic form. Various reports show values as low, adequate, or high. A number of reports show actual values found for each parameter. Reporting styles also vary regarding the reporting of desired levels, sufficiency levels and base saturation percentages. What style are you most comfortable with? A combination of these styles may be most helpful.

Units of measure can vary from parts per million, pounds per acre, pounds per 1,000 square feet, or kilograms per hectare.

It is very important that the laboratory is aware of your sampling depth if you will be receiving your results in a pound per acre or pound per 1,000 square feet format. The sampling depth will affect the value reported. It is vital to be aware of units when comparing reports from different laboratories. You have to compare apples to apples. Looking at a phosphorus example again will explain this. A laboratory may report phosphorus at 50 ppm P and another may report it at 229 pounds per acre P2O5. These two results are the same; however the units are the difference.

Does the soil report offer a recommendation? Where did it come from? Some recommendations are generic computer recommendations that give a ballpark range for optimum levels of nutrients. These may or may not be for a specific geographical area. If you are growing a unique or exotic crop, then you may need some specific advice. Inquire about the services of an independent agronomist.


How do you get your sample to the lab? Most labs will provide a soil sample bag or suggest a suitable alternative. Soil laboratories receive hundreds of samples each day. Be sure to acquire the appropriate paperwork from the laboratory to submit with your sample. Incomplete information will only delay the processing of your samples. Packing your samples for shipment is very important. Be sure to pack the samples tightly in a box. Pack newspaper or other packing material around the samples to keep them from bouncing around in the box.

If samples can move around during shipment, they sometimes break open and can be destroyed. Resampling will add to your cost in time and money.

How long will this process take? Turnaround time in the whole soil testing process is imperative. Laboratories under stand that your test results can be time sensitive. Don’t hesitate to contact the lab if you have an emergency situation and need “rush” service. To determine your approximate turnaround time, consider the time it takes to get the sample to the lab (two-three days) and perform the analysis (three-four days).

Turnaround time varies from one lab to another and also varies by season. You may want to contact the lab to inquire about their current turnaround time. How do you get your report? You do not want the report held up somewhere after you have already waited through shipping and testing procedures. Reports are usually emailed or made available on the internet on the same day the testing is completed. Be sure your correct email address and/or a fax number is submitted with your samples to get your results as soon as possible.

This is just the tip of the iceberg when looking at differences in laboratories. Laboratory instrumentation is continually improving. More parameters can be detected in a short amount of time and detection limits keep getting smaller. More efficient and “green” procedures are always being investigated.

Embrace the advancements. Visionaries like Dr. Albrecht are still being cited in soil analysis circles. If he was continuing his research today, I believe he would embrace the latest technology and tools available.

So, the question still looms … which laboratory is best for you? Take the time to do your homework. It will be worth the investment and you will receive the value that you expect. Explore laboratory websites, call a lab and ask some questions, ask your friends about their experiences. Make sure you acquire the appropriate paperwork and instructions from the lab that you choose.

When you have selected a laboratory that meets your needs and you are comfortable, stick with it. Jumping from lab to lab will only discourage you on your quest to improving soil fertility.

Editor’s Note: This article appeared in the October 2011 issue of Acres U.S.A.

A Guide to Reading Soil Test Results

By Charles Walters

What is a Soil Test?

A reliable soil test includes three parts:

  • Proper sampling, with field and cropping history, and yield goals.
  • Chemical tests for nutrients available for crop growth.
  • Reliable recommendations for nutrients and amendments needed to attain desired yield goals.
Klaas Martens: Soil, Testing & Fertility from the 2009 Eco-Ag Conference & Trade Show. Listen in as the popular agronomist and successful organic farmer teaches his methods for managing soil testing, data and inputs.

Reading a Soil Test

The following is how laboratory results are reported at Texas Plant & Soil Lab — other labs utilize similar terms.

Texture — Ranges from 1 (sand) to 3 (loam) to 6 (heavy clay)

Cation Exchange Capacity (CEC) — Texture determines the CEC. Textures of 1 = 3-8 CEC. Textures of 6 = 30-50 CEC.

Organic Matter (O.M.) — Humus increases CEC. About 3.5 CEC increase for each percent increase in humus. O.M. improves tilth (soil physical condition), water and nutrient holding capacity. The more the better. Ideal O.M. levels for corresponding texture levels (1-6 respectively) = 2.8, 3.1, 3.6, 4.1, 4.5, 4.8.

Natural Extracting (CO2) — Plants produce natural carbonic acid in the root zone which can be used to obtain nutrient values that are more realistic and calibrates to the plant uptake.

NO3 (N) — This highly soluble nitrate ion moves easily up and down with water and is a constantly changing value. Plant uptake is rapid. Excess can be toxic.

P2O5 (P) — Extracted with CO2, the amount is reported in pounds per acre for the top foot of soil. The amount reported is available to a crop in a normal growing season. Responses can be expected below 40 pounds per acre and high phosphorus requiring crops may respond to additional phosphate of up to a 200 pounds per acre tested.

Potassium (K) — Extractable using CO2. This is the amount available to the crop in a growing season. Readings range from of 80 ppm to 120 ppm for crops with high potash needs. Soil availabilities vary with texture, soil moisture conditions, interference from sodium levels and ratios of Na, Ca and Mg.

pH — The acidity measurement is variable. Most crops prefer a pH between 6.5 and 7.3. Neutral is 7.0, above is alkaline and below is acid. The desirable pH level is a nebulous, dynamic determination that is highly variable.

Electrical Conductivity (EC) Salts — This is a measure of total water-soluble salts expressed as mmhos/cm. EC x 640 = total dissolved solids in ppm.

Salt Cations — Water-soluble cations determined by the atomic absorption spectrophotometer. Calcium is important and should exceed 100 ppm.

CO2 extractable (carbonic acid equivalent) is the same as the plant root process. Sodium is the main extractable harmful element and should be below 180 ppm. The amount of extractable calcium reserve in the soil is also reported and must be known to properly manage excess salts.

Na (CO2)/Ca (H2O) and Na (CO2)/Mg (H2O) — These ratios help evaluate salt problems and are indicators of the soil’s physical con­dition for water, air and root penetration. The Na:Ca ratio should be less than 6 for good internal drainage. The Na:Mg ratio should be below 20 for regular crops and below 10 for sugar-producing crops such as melons, citrus, sugarcane, etc.

Source: Ask the Plant

Examples of How to Adjust to Your Soil Test Results

By Neal Kinsey

Reading your soil test and knowing what to do are two different things. Here are some examples of how to apply results to your fields based on what your soil test is indicating. It will give you confidence that you are on the right track to increasing your overall soil health.

Except in the case of wheat and other small grains, if the soil test indicates that you need ten pounds of copper sulfate but that amount represents a cost that is too high, you could consider putting on two pounds for the next five years instead of ten pounds all at once. You can build copper levels this way because that nutrient is so stable in the soil. Almost every soil analyzed is deficient in copper. The few exceptions are where there is natu­rally occurring copper in the soil or where manure has been used, or along rivers where soil has been moved in by constant flooding, and where alluvial deposits keep the soil built up. The other place where we don’t have copper deficiencies is where large amounts of pesticides containing copper have been used in the past, and where turkey litter is commonly used.

When crops on soils with adequate fertility that test low in copper fail to respond to copper applications, a molybdenum test should be considered. Both need to be present in adequate amounts, since either one can influence the amount a crop can take up of the other one.

A farmer from Iowa I had worked with for eight years called me one day. He said he had a problem with some of his corn going down. He wanted me to look at the soil test. He had 80 acres split into four 20s, and one had a 1.5 copper, his lowest level. I told him that his copper was 1.5 ppm and he was going to have the weakest stalks there. It was true. He said, “Well, since that is true, what about the next field?” We went through all the data until he hit 2 ppm. In each case he lost corn from lodging, but the lower the copper level below 2 ppm, the worse the corn was lodged.

Copper gives resilience to a plant. The other key to flavor after sulfur is copper. Copper doesn’t move in the soil. If you see a copper deficiency at all, it is like sulfur. It shows the deficiency in the young­est growth first. Adequate nitrogen means you get better copper uptake. Too much nitrogen means you actually decrease the avail­ability of copper to the plant. Wheat is a crop that responds well to copper. If the other needed nutrients are adequate, but you are below 2 ppm copper and you put enough copper on your wheat to get above 2 ppm, it will produce an extra five bushels (300 pounds/acre) of wheat.

I was asked to make a consulting trip to Germany in 1985. The client who asked me there had arranged for speaking engagements to several groups of farmers. He told me to tell them just what I had done on his farms. In Germany, they use the taller varieties of wheat, but they also use growth regulators to keep plants short. When the subject turned to copper, I mentioned that if the soil had below 2 ppm and copper was put on, it would increase yields by five bushels per acre. I also told them that every soil I had checked in Germany was below that level. One man raised his hand, stood up and spoke for two or three minutes. The interpreter leaned over and said, “This is the man who is in charge of fertility for the university in this area. He is telling the farmers why they don’t need to really worry about the copper that you said should be put on.” When he had finished, a doctor of fertility research rose and reported a ten-year study (unknown to me) just completed which had shown exactly the same results I had mentioned on wheat production.

Copper sulfate, 22.5 or 23 percent, is water-soluble and can be applied to soil or as a foliar. A word of caution here. When cop­per is mixed in solution with other elements it may show as compatible in the mix, but use it up. Do not let it set in your spray tank, pumps or hoses overnight. It can harden to the point that the entire spraying apparatus has to be scrapped. I won’t bother with other copper sources if I can get copper sulfate because I know it works, and I know how much can be applied safely. A ten-pound application of copper sulfate—after 12 months time—will raise the copper level by 0.6 ppm on the spe­cific test we use. A copper level is the easiest to build and main­tain, and zinc is next in the pecking order. Both have staying power in the soil.

Zinc aids in the absorption of moisture. Along with potassium, think of zinc in critical moisture situations. It also helps transform carbohydrates. It regulates plant sugar use. Zinc plays a role in enzyme system functioning, as well as with the growth regulators normally present in the plant and protein synthesis.

Consider zinc needs, especially in sensitive crops such as corn and grain sorghum, also soybeans and dry beans. As far as zinc levels are concerned, the minimum is 6 ppm. Below that, enough should be applied the first year to get up above the 6 ppm figure. There has never been a soil—in my experience at least—that required more than 30 pounds of zinc sulfate to completely take care of the worst zinc deficiency, provided limestone didn’t have to be applied at the same time. If lime is applied, the lime won’t drive out the zinc, but it will affect zinc availability. If you need zinc and lime and put on the lime but don’t put on the zinc, expect your zinc level to get worse. Zinc probably gives a response more often than any other micronutrient when it is applied for crop production. I see many soils that need zinc. All can be taken care of, generally with excellent response. Only a few crops do not respond well to zinc when only slightly deficient, one of them being wheat. Again, for zinc, 6 ppm is the minimum. Excellent means at least 10 ppm, and an excess is 35+ ppm.

A classic sign of zinc deficiency in corn is the whitish stripe in the leaf color, which looks much like a magnesium deficiency. In the field, often I can’t tell whether it is a zinc deficiency or a magnesium deficiency. The difference between zinc and magne­sium deficiencies should be that zinc will be white and magne­sium will be white on top with a purplish color on the bottom.

High phosphorous, high calcium or high potassium levels can induce zinc deficiencies as does the overuse of nitrogen. Also, as the pH goes up from 6, when a soil has good zinc levels, availability begins to decrease. It can go as high as pH 7 before it decreases good zinc availability to the point that it becomes a problem. Heavy cuts, such as when the field has been graded or the topsoil has been taken away, or when eroded soil allows sub­soils to appear, strong zinc deficiencies become evident.

Zinc is not easy to leach away. It is held well on clay and humus. Once zinc levels are improved, it is relatively easy to keep them up. When zinc sulfate is applied on the tests we have, an exact relationship between the amount of zinc applied and the increase shown on the soil test can be expected. Using 36% zinc sulfate at an application of 10 pounds per acre will exhibit a 3.6-pound increase of zinc on the test. The correlation is classic. Putting on ten pounds of 36% zinc sulfate means putting on 3.6 pounds of zinc per acre. A soil test — when the zinc is finished breaking down — should show an increase of 3.6 pounds of zinc. That translates into 1.8 ppm, meaning every 10 pounds of zinc sulfate applied will raise the zinc level by 1.8 ppm. There is one other thing to be remembered about pure zinc sulfate. Put on ten pounds of zinc sulfate today, then come back next year and pull a soil test on the same day. That zinc is only going to be halfway to its final level. You are only going to see a 0.9 ppm increase in the soil. When you put on sufficient zinc it will not reach the desired level for two years, but will supply enough zinc for the crops grown for both years.

Some firms say they have a 36% zinc product, it being a 36% oxysulfate. It is cheaper at the counter, but it does not always build zinc levels. There are some zinc oxide products that have been pulverized and then prilled, which have also proved effec­tive for increasing the levels in the soil. Apply ten pounds, the same as with 36% zinc sulfate, and see if next year the deficiency is still there. Pure zinc sulfate is the sure choice.

With the exception of boron, on most soils the technology exists in order to build the levels of trace elements to a point that it is not an annual expense, but basically an initial expenditure. Then afterwards, it is a matter of testing and fertilizing as need­ed over the years to keep the levels up. Many farmers, ranchers and growers initially resist the addition of trace elements to increase fertility levels, objecting to the added expense. But when you consider the years spent taking from the soil without adding the traces back, replenishing should be expected. And supplying those micronutrients have helped increase corn yields by 20-30 bushels, and wheat from 5-25 bushels per acre. Micronutrients, when applied in the right form, to build up the levels in the soil will help quality and crop yields accordingly.

Some farmers who have livestock have always felt they shouldn’t have to be concerned with trace elements because their manure or compost would take care of it. I work with many farmers who use manures and compost, and this is rarely the case. Think about it. When a soil is deficient in copper and adequate copper is not being supplemented, how can enough be in the manure? Manure is generally low in sulfur, boron and copper—the nutrients most often lacking in our soils used for growing the crops. Keep in mind, when manure is applied, you can influence the soil nutrient level to only the extent of what is there in the first place. Nevertheless, manure is certainly helpful and in certain soils even sufficient to keep the trace elements that are present in a soil most available for plant use, while at the same time helping to recycle those that are picked up in the feed. And therefore, as the use of manures in an area declines, the need for trace elements will increase.

Most soils we analyze just do not have an adequate supply of trace elements to assure that the crop will do its best. So keep in mind that just because there are enough of the major elements for the crop, does not assure that trace element levels will also be adequate.

Under the present economic circumstances, every farmer needs to have the confidence that he is on a solid footing, and doing all he can to supply his crops the fertility needed from start to finish. The misconceptions and misunderstandings about soil fertility make this even harder to accomplish. The more farmers or those involved in a soil fertility program understand the reasons behind micronutrient recommenda­tions, the more confidence there will be in those recommenda­tions and the decisions made on how to use them. The lack of any nutrient, whether needed in major, secondary or trace amounts, hurts the soil and all that must live from it.

Source: Hands-On Agronomy

How to Read a Soil Test

By Charles Walters

The first step on the road to achieving healthy soils able to sustain productive plants is the soil or plant analysis test. For optimum results, the initial test relies heavily on proper sampling.

Quality samples submitted to the laboratory and excellent testing methods can produce the most accurate results possible but without an interpretation of the nutrient recommen­dations that speaks to the grower — all may be for naught.

Graphs and charts filled with color-coded lists of numbers speak volumes to those that know how to read them. But the uninitiated may glean just a fraction of the total message.

A soil or plant analysis test from a quality laboratory contains much more than just the raw data. Using an integration of field and cropping history with the test results, interpretations and recommen­dations are formulated to tell the grower the meaning behind the num­bers. It is these soil and plant test interpretations and recommendations that matter most and have the greatest benefit for many people.

Agronomist Esper K. Chandler, author of Ask the Plant and founder of TPS Lab, was asked to look at several plant and soil analysis tests from different crops and give his expert interpretation of the results. The results are below. For each example, Chandler’s com­ments offer new insight and enlightenment about what the results said to him. The soil and plant test samples presented in this chapter are actual real-life examples included here with Chandler’s dictated interpretation and recommendations — presented so others can gain a deeper insight into the important messages held within. For each example, the most important messages have been highlighted and explained by Chandler.

Above: A Guide from TPS Lab on Compost STA Test Reports. 

Source: Ask the Plant;