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Supplying Nitrogen: Tap into Nature

Human activity is affecting planet Earth to such an extent that natural scientists are naming this time the beginning of a new geological age/epoch called Anthropocene (the recent age of man) and ending what was the Holocene epoch (about 17,000 years ago to present).

We are no longer observers of nature, but significant influencers of what is happening to nature. The sheer weight of humans and their livestock is now bigger than the Earth’s wild animal population. Our activities are rapidly increasing the amount of CO2 in the air. That is an established fact, the effect of which is the only thing in dispute, i.e. will it get warmer or cooler and will we be wetter or dryer?

The temporary warmth is obvious in the Arctic. Although growers usually help to absorb CO2 by growing crops, their improper handling of crop residue or improper feeding of livestock can add the CO2 back into the air. However, farming’s bigger polluting effect concerns nitrogen.

Plants have always used N from the air by a variety of natural methods. Now the rate we are taking N out of the air is 50 percent higher than what nature has done for millions of years. Most of this industrially created N is now used for fertilizer. This industrial process was originally used to make munitions prior to World War I.

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Soil Testing: The Need for Total Testing

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.

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

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.

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. Continue Reading →

Soil Organic Matter: Tips for Responsible Nitrogen Management

For soil organic matter to work the way it should, it depends on a careful balance of nutrients and minerals, including one of

Healthy, homegrown carrots in rich soil.

the most important elements — nitrogen. One of the great paradoxes of farming is that lack of nitrogen is regarded as one of the great limitations on plant growth, and yet plants are bathed in it because the atmosphere is 78 percent nitrogen.

Most plants cannot use nitrogen in this form (N2) as it is regarded as inert. It has to be converted into other forms — nitrate, ammonia, ammonium and amino acids for plants to utilize it.

In conventional agriculture most of these plant-available forms of nitrogen are obtained through synthetic nitrogen fertilizers that have been produced by the Haber-Bosch process.

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Humic Acid: The Science of Humus and How it Benefits Soil

Humic acid is a group of molecules that bind to, and help plant roots receive, water and nutrients. High humic acid levels can dramatically increase yields. Humic acid deficiency can prevent farmers and gardeners from growing crops with optimum nutrition. Conventional wisdom today ignores humic acids, though, holding that it is impossible to grow and maintain an urban landscape such as a park, golf course, or lawn without high-analysis NPK fertilizers.

This article will drill down into the details on humus. We can adjust our soil biology and chemistry and achieve better yields if we understand its characteristics.

Humus vs. Organic Matter

We must begin by understanding that there is a difference between soil organic matter and humus. “Humus” is a general term that describes a group of separate but distinct humic substances. “Soil organic matter” is material that is decomposing at various rates in the ground.

Some of the most common substances we collectively refer to as “humus” include:

  • Fulvic acid: a yellow to yellow-brown humic substance that is soluble in water under all pH conditions and is of low molecular weight.
  • Humic acid: a dark-brown humic substance that is soluble in water only at higher soil pH values and is of greater molecular weight than fulvic acid. Humic acid may remain for centuries in undisturbed soil.
  • Humin: a black humic substance that is not soluble in water at any pH, has a high molecular weight, and is never found in base-extracted liquid humic acid products.
Humic acid

Adding a small amount of humus to an acre of soil can achieve positive results.

Applying organic matter is certainly an excellent way to remineralize a soil that has been leached or has no chemical reactions, such as with some sands. Sand with a low cation exchange capacity (CEC) has difficulty holding onto the cations of nutrients, and these cations can easily leach deep into the soil and become unavailable for plant uptake.

Sandy soils are also unable to hold onto water when arid conditions prevail and humus is lacking. Sands reside in a condition of “feast or famine,” since water and nutrients are only available for a short time after they are applied. Biomolecules of humus can help retain water and the ionized nutrients that are produced by the natural cycling of organic biomass, compost, or other sources of fertilizer.

The electronegativity factor of humic acids is key in developing and maintaining a healthy and sustainable soil. The source of these humic acids in a sustainable agricultural program, organic certified farm, or urban landscape can be decaying organic matter such as compost. In essence, this is fertilizer in an organic form. It is therefore important to know the ingredient source and the nutrient analysis of your compost.

Humus is powerful stuff, and a tiny amount can produce a huge measurable result. We have seen as little as 40 total pounds on an acre of farmland increase the yield of a crop dramatically.

The Physics of Humic Acid

Humic acids are extremely important as a medium for transporting nutrients from the soil to the plant because they can hold onto ionized nutrients, preventing them from leaching away. Humic acids are also attracted to the depletion zone of the plant root. When they arrive at the roots, they bring along water and nutrients the plant needs.

Humic acid and grass root system

Humic acid brings nutrients directly to plant roots.

The depletion zone is the area close to the root of a plant from which the root draws (depletes) nutrients. This zone can become particularly depleted if there is a lack of either humic acid or mycorrhizal fungus. When plants are mycorrhizal, the depletion zone is of less importance. Mycorrhizae have hyphae micro-tubes that can extend much further into the soil than the host plant can reach. They can gather mineral nutrition for the benefit of the host plant from outside the depletion zone. Humus is even more critical for plant nutrient availability and uptake if there aren’t healthy mycorrhizal relationships in the soil.

Positive ions are more easily absorbed by a plant’s root because the root has a negative charge. In other words, the positive (cation) is attracted to negative (the living root). Humic acids hold cations (positive ions) in a way they can be more easily absorbed by a plant’s root, improving micronutrient transfer to the plant’s circulation system. This works because humic acids (ulmic, humic, and fulvic) pick up positive ions and are then attracted to the root depletion zone and to the hyphae micro-tubes of mycorrhizae.

Since the root’s negative charge is greater than humic acid biomolecules’ negative charge, scientists theorize that the micronutrients are taken up by the plant’s root and are absorbed by the plant’s circulation system. Some of the micronutrients are released from the humic acid molecule as they enter the root membrane, but we are now realizing that the plant will also uptake some of the lighter molecular-weight humic acids as well. In essence, the humic substances are chelating such cations as magnesium (Mg2+), calcium (Ca2+), and iron (Fe2+). Through chelation, humic substances increase the availability of these cations to plants.

How to Build Humic Acid Levels

Compost and other sources of decomposing organic matter are not an efficient way to build soil humus levels. Compost rapidly decomposes and leaves its minerals behind, releasing carbon into the atmosphere as CO2. Humic substances, on the other hand, are stable, long-lasting biomolecules. Components of humus have a mean residence time (based on radiocarbon dating, using extracts from non-disturbed soils) of 1,140 to 1,235 years, depending on the molecular weight of the humic acid.

If you really want to fix or rehabilitate a soil, increase its CEC, improve its tilth and porosity, improve water availability for conservation, and therefore make a soil a healthier terrestrial biosphere for all plants, roots, microorganisms, you must depend on humus. Humus is a product of soil chemistry, and is dependent upon a source of its precursor chemicals: amino acids.

Amino acids are the building blocks of protein. The best source of the amino acids in a natural ecotone are produced by the Glomus species of mycorrhizae. These are associated with any grass in a natural, undisturbed site. The tallgrass prairies of the Midwest exemplify this soil-building process better than any ecotone on earth, because grasses utilize a Glomus-mycorrhizal relationship. This is why there is was so much humus-rich topsoil in the Tall Grass Prairies. Glomus makes a soil protein called glomalin, a substance that is rich in amino acids. Combined with humus, they create a huge carbon sequestering and banking factor.

Scientists can measure the percentage of calories in compost that come from proteins (the amino acids), carbohydrates, and fats. This enables them to measure the lack of humus-making potential of compost. Even in supreme-quality compost, the percentage of calories coming from amino acids (protein) is less than 5 percent. Since it is difficult to rely on the perfect amino acid ratio in compost because of differing manufacturing quality controls and ingredient consistency, we cannot predict a 100 percent efficient conversion of all these amino acids into humic substances. Compost or other soil amendments of organic matter are therefore not a reliable way of increasing soil humic substances.

Attempting to add adequate amounts of humic acid through application of compost would require such a huge amount that it could lead to overdosing the site with nutrients. In fact, the better the quality of the compost, the more concentrated the nutrients will be, and the less you should use. In the case of our TTP Supreme Compost, for example, we recommend using it sparingly – never more than 60 pounds per 1,000 square feet or 2,600 pounds per acre. And this is assuming no other fertilizer is being used at the same time.

Humus supplementation is necessary if you want humus. You can measure the quantity of humic acid in a compost product at a qualified lab. A good quality compost will measure around 5 to 8 percent humic acids.

Benefits of High Humic Acid Levels

One obvious benefit of humus we have seen at our Arboretum in Los Lunas, New Mexico, has been the aggregation of clay. This aggregation has made the clay more porous, soft, and aerobic, with better drainage, resulting in deeper root growth of all plants. The site was purchased in 1986 with clay soil 12 feet deep and a pH ranging from 8.3 to 9.2 – so alkaline that in the winter the site would turn white.

Today we have one of the largest oak species collections of the Quercus genus in the United States, and the largest collection of native oaks of the Chihuahuan Desert Region in North America. Also on the site are several types of redwoods, maples, dogwoods and giant timber bamboo. None of these plants should be able to grow on soils with the conditions we started with, but with the power (or magic) of humic acids we have rehabilitated the soils to a productive and healthy level.

Finally, “Humic Acids: Marvelous Products of Soil Chemistry” (The Journal of Chemical Education, December 2001) states, “Humic acids are remarkable brown to black products of soil chemistry that are essential for healthy and productive soils. They are functionalized molecules that can act as photosensitizers, retain water, bind to clays, act as plant growth stimulants, and scavenge toxic pollutants. No synthetic material can match humic acid’s physical and chemical versatility.”

By Michael Martin Meléndrez. This story was first published in the August 2009 issue of Acres U.S.A. magazine.

Organic Nitrogen: When are Nitrogen Units Not Nitrogen Units?

Organic nitrogen and inorganic nitrogen: what’s the difference?

A farmer gives a plant organic humus fertilizer to plant.

Organic growers frequently attempt to quantify the amount of organic nitrogen they add to their soil ecosystems in the same manner that conventional growers use inorganic nitrogen units to calculate their nitrogen requirements. Logically, they reason that a ton of organic material with 4 percent nitrogen content as verified by a laboratory test will provide 80 pounds, or units by some determinations, of nitrogen.

The truth is that organic nitrogen sources vary in their efficiency of transformation into soil components over a much broader range of response than do inorganic synthetics, which offer precision measurement and a repeatable predictability of release. Use of inorganic nitrogen units to determine nitrogen needs for organic growers is therefore problematic. A popularly available and reliable conversion algorithm between tested inorganic nitrogen and untested organic nitrogen in organic soils does not exist, however. Without such an algorithm there can be no scientific basis of comparison. Continue Reading →

Soil Carbon: Changing Dirt into Soil

Soil

Soil carbon’s role in creating healthy topsoil is becoming a global topic.

It’s a popular notion that humankind is contributing excessive amounts of carbon into the atmosphere in the form of greenhouse gas. There’s been debate on what can be done to correct this situation, going so far as to suggest methods of sequestering the carbon into places of long-term storage. Regardless of who’s right or wrong, it can’t be debated that the definition of a healthy topsoil is when the soil has a rich concentration of durable carbon compounds that change for the better the chemical, physical and biological nature of the soil.

I heard recently a Ph.D. horticulture specialist say that you cannot add too much compost to a soil and that compost was the key to building and preparing a soil. In fact, he published on his university’s letterhead a statement where he recommends adding as much as 6 cubic yards of compost to an area of 1,000 square feet while preparing the site for landscaping. I heard a similar statement was made at a Santa Fe nursery seminar by a guy who makes compost. Well, that statement may be true if the compost was still composed of extremely decay-resistant woody material that was also low in nutrients, but then it would not be compost.

Photo by the author.

Photo by the author.

The simple act of composting is where specialized fungi and bacteria called saprophytic microorganisms collaborate in the reduction (shrinkage) of organic matter by utilizing the calorie value of the fats, proteins and sugars contained in the organic matter. As the microbes eat, they are concentrating all the parts that cannot be eaten, such as the minerals and the humic substances (HS). If plentiful levels of oxygen are available, the microbes that need oxygen to function will do the composting. A bi-product of their work will be CO2 which the microbes liberated from the carbon that was part of the digestible (decomposable) organic matter — the proteins, the fats and the sugars (carbohydrates). We call this source of carbon “rapid cycling carbon,” as it simply will not persist in the soil as part of the long lasting carbon bank that defines a topsoil. The part of a topsoil that defines the very essence of the soil is the concentration of the carbon substance that is not rapid cycling, and which has a resonance time in the soil of thousands of years. These carbon molecules are powerful biologic chemicals of nature called humic acids (HA or HAs), which are contained within the whole material called humic substances. They are not food for microbes, fungi or bacteria, therefore, they are not decomposable and will persist for a long time. Compost is a poor source of these substances, which any commercial soil lab can verify by doing a humic acid extraction and assessment. Levels of 1 to 5 percent humic acid are typical of a high quality finished compost, which is insignificant and inadequate to expect compost to fulfill the objective of building soil carbon directly.

For this reason, you simply can’t add enough compost to make a difference without overdosing the soil with nutrients! This also makes the term humification in my opinion an obsolete term, since that term implies that composting (decomposition) of organic matter results in the formation and high concentration of humic substances, which it does not! If it did, we would see levels much higher than 5 or even 25 percent humic acid in commercial compost, which we rarely see unless the compost was salted (fortified) using humate/leonardite.

Soil Carbon and Compost

Carbon found within the molecular structures of proteins, fats and carbohydrates (sugars) is turned into CO2 when oxygen is plentiful and aerobic saprophytic microbes can do their work. If O2 is not plentiful, then only those microbes that can function anaerobically (without air) can do the decomposing. This is not good, because toxic chemical compounds are the byproduct of anaerobic organic matter decomposition.

Compounds such as lactic acid and alcohol are produced when oxygen is not available in adequate amounts and those chemicals are toxic to plants at even parts per million. Anaerobic metabolism can occur in our muscle tissue as well, when we are out of shape and have poor vascularity (blood flow) in the muscles. This causes poor gas exchange during exercise and the muscle cells will not have adequate levels of oxygen, resulting in the production and accumulation of lactic acid. The lactic acid is toxic and irritating to the cell walls of your muscles and nerve endings and you consequently will feel pain a day or two after you workout. So it doesn’t matter if we are talking about soil, or we are talking about our own bodies, we must have adequate amounts of oxygen at all times in order to have optimum health.

Soil Carbon and Compost Limits

So we don’t want compost that is produced without oxygen, but here’s the other side of the problem when we look back at the original statement “that you can’t add too much compost.”

Humic substances accumulatingYou can indeed add too much compost, and for many reasons, one of which is back to the problem of oxygen. Here’s how and why; the more decomposable organic material you have, the more microbes will want to get into the act therefore, the more oxygen will be needed to accommodate this feeding frenzy. We call this the “BOD” or the Biological Oxygen Demand. If you incorporate into the soil too much compost that still contains a lot of combustible organic matter, the resulting population explosion of saprophytic microorganisms will rapidly use up the oxygen and your soils will go anaerobic. This results in a whole slew of unhealthy conditions, including the production of lactic acid and alcohol, two chemicals that are toxic to plant roots.

The other problem with adding too much compost is that if it is really compost and if it is made from a source of nutrient-dense plant organic matter, it will contain a rich and concentrated source of plant nutrients. After all, who do you know that is intentionally looking for a poor nutrient source of organic matter in order to make their compost? That would be silly, plus you may not achieve the proper carbon to nitrogen ratio needed to actually instigate the composting process. If you made the compost using the proper carbon to nitrogen ratio, by default your finished product will contain a significant amount of nitrogen. The bulk density of compost can easily be 40 to 50 pounds per cubic foot, which is 1080 to 1350 pounds per cubic yard. If you add 6 cubic yards of compost, as suggested by the University Ph.D. for a total of 7,800 to 8,000 pounds of compost per 1,000 square feet, you have also added over 103 to 106 pounds of nitrogen, a toxic amount! On a per acre level, that’s approximately 4,600 pounds of nitrogen, an amount that no farmer on earth would dare apply. So yes indeed, you can add too much compost!

As I’ve already described, the carbon found in over 95 percent of the carbon-rich parts of a compost are easily and rapidly decomposed into CO2, which defends my claim that compost is the wrong tool in the tool box, needed to accumulate carbon into the soil. The purpose of this tool is that it could potentially be a source of plant available nutrients if the composter was actively utilizing nutrient dense sources of plant organic matter.

As a fertilizer, compost can nutritionally support vegetation and it is then that we see a more efficient and effective development of topsoil, only because the plant is better at photosynthesis! If the plant is better at photosynthesis it can convert more atmospheric carbon into biological carbon called glucose, which is then transported down into the roots and provided to the bacteria and the mycorrhizal fungus. “Root Exudates” are liquid glucose leaking into the soil from the roots of plants.

Soil Carbon and Humus

In the same article, May 2011 issue of Discover Magazine, my 30-year long opinion of where humus comes from is finally collaborated by another source. Humus does not come from humification of dead organic matter; rather, it’s a result of an efficient mutualism between plants and the terrestrial biosphere of soil microorganism, and most specifically the mycorrhizal fungi. The mycorrhizal plant fungi relationship is critical to the process of pedogenesis, because it’s the massive contribution this fungus makes to its host plant in the form of water and minerals that allows the plant to be healthier and to live longer. Science has demonstrated that when a plant is mycorrhizal, the uptake of minerals from the soil is dramatically better and the drought tolerance of the plant is also significantly better.

Once again, a healthier and longer living plant can contribute more carbon in the form of liquid glucose to the soils terrestrial biosphere and from there everybody gets fed. Be clear that almost without exception, farm soils worldwide are lacking a strong mycorrhizal component therefore, expecting humus to accumulate in those same farm soils is most likely not going to happen. Also, research has proven that plants must have the benefit of this amazing fungus in order to get those minerals out of the ground in a useful fashion and with the minerals comes water. This is how we grow a nutrient-dense crop and also grow soil. For farming, mine reclamation, landscaping, highway re-vegetation, and other venues where you hope to build soils, you must inoculate with a mycorrhizal product, if you expect to see these benefits.

In 1974 I described this relationship as the “Soil Food Web,” a process of soil formation and collaboration, where most terrestrial life benefits from the Bio-Geo-Chemical process of mineral nutrient sequestering and availability. The term humus is one used by the average person, but its technical description used in chemistry is humic substance! The term humic substance describes a whole bunch of carbon rich compounds that resist decay and which are products of soil chemistry. Within the whole substance is a chemical of nature called humic acid. While humic acids are powerful chemicals with many characteristics and benefits, it’s the whole substance of humic compounds that are the major bank of long lasting carbon in the soil, resulting in the formation and accumulation of a rich topsoil.

But What About Soil Compaction?

The large, air-filled spaces, or “macropores,” in untilled soil without compaction, often resemble the branching vessels of the human circulatory system. A team of Nordic researchers led combined computed tomography (CT) scanning with traditional measurements of air exchange to “diagnose” the long-term impacts of soil compaction on the hidden, but vital, soil pore network. When scientists examined cores of heavy clay subsoil suffering from compaction on a research site in Finland, they found the macropores were greatly affected compared with a non-compacted control soil. The compacted soil contained mostly long, vertical “arterial” pores, or pipes, with significantly fewer marginal pores branching from them.

Most troubling to the researchers was how lasting the impacts of compaction appear to be. In the study, the group examined soil cores taken from a depth of 0.9 to 1.2 feet in plots where 30 years earlier a heavy tractor-trailer drove over the ground four times to create compaction in an experimental treatment.

It’s where a lot of farmers end up at some point, with dirt. And turning it into soil starts with understanding carbon.

By Michael Martin Meléndrez. This report on soil compaction appears in the April 2014 issue of Acres U.S.A. magazine. This story originally published in October 2011 issue of Acres U.S.A. magazine. Michael Martin Meléndrez and his wife Kari, own Soil Secrets LLC, Soil Secrets Worldwide LLC, and the Trees That Please Nursery. Contact Soil Secrets and Michael by calling 505 550-3246, or email soilsecrets@aol.com.