Compose™ Sodium Reclamation

Scientific Background Information Regarding Remediation of Saline/Sodic Soils With Plant Health Technologies™ COMPOSE™ Products

For over 25 years Plant Health Technologies™ soluble humus supplier, Horizon Ag-Products™, has specialized in the production and use of humus derived organic acids products for agriculture. These products were first applied to improve
soil tilth and increase crop growth and yields, 11. Academic research and extensive field trial studies have shown how they also reduce the toxicity and burn from chemical fertilizers and improve the efficiency of nutrient uptake by crops, 15.
Over the years, we noted that the most dramatic improvements in crop and turf yield were often on saline or sodic soils, or where irrigation water was unusually salty. In recent years our staff has conducted a dozen or more studies in the field that showed dramatic improvements in soil conditions and crop response when the products were added to salty or sodic soils or irrigation waters. Based upon our knowledge of the active ingredients and modes of action involved, we have f formulated certain products specifically to deal with salinity reclamation situations.

"Comparative soil samples indicated reduced soil EC levels and lower sodium, SAR, and ESP numbers."

A Review of the Scientific Literature

The effects of humus derived organic acids on soils and plants has been surprisingly well documented in the literature. Impacts of humic substances on soil structure have been studied in great detail. Studies on the effects of these substances on plant growth and nutrient uptake are even more extensive. There are literally hundreds of studies chronicling the beneficial effects of these compounds on plant nutrient uptake and for the mitigation of various toxic herbicides and heavy metals. Affects of humic substances on sodium and on salinity in general, however, have not been adequately studied. What we know about these effects can be deduced by our knowledge of the chemistry and modes of action of the active ingredients viewed in the light of what we have learned in the field from recent trials.

Impacts on Soil Structure

It is well understood that sodium causes soil particles to disperse from one another and destroys soil aggregation and good soil structure. Sodic soils crust easily and have characteristically poor water infiltration rates. Sodium dominated soils are often hard to work into a good seedbed. The mechanisms of how humic substances work together with calcium to counteract sodium’s effects have been thoroughly studied. Allesandro Piccolo is a leading researcher in this field. His reviews of this subject are particularly insightful11,12. Using humic substances from oxidized coal (lignite) and organic soils, he has demonstrated that relatively low rates have profound impacts on soil structural improvements including: 1) flocculation of clays, 2) formation of water stable soil aggregates, 3) water infiltration, 4) runoff and erosion reductions, and 5) even available water holding capacity. Figure 1 below shows results from a study12 where various rates of organic acids from lignite successfully amended soils, improving their structure.

Soil aggregate size vs organic acid applications

Remediation of Contaminated Soils and Waters

The scientific literature abounds with studies on the use of humic substances for remediating soils contaminated with pesticides16, heavy metals13,14, and other pollutants5. Other studies focus on the remediation of surface and groundwaters5 contaminated with the same constituents. Although the modes of action described in these studies provide insight into how humic substances help amend saline and sodic soils and waters, there are no studies to date that directly address the salinity and sodium issue directly.

Horizon Ag Products™ / Plant Health Technologies™ Sponsored Field Research

We have conducted numerous field trials throughout the Western United States comparing soils or waters treated with COMPOSE™ DC & COMPOSE™ liquid on saline or sodic soils. Using the dry granular product COMPOSE™ DC at broadcast rates of 40 to 150 lbs/acre, yield increases have consistently ranged from 10 to 30% on alfalfa, tomatoes, cotton, potatoes, and other crops. In most of the studies there was an increase in plant population and plant height in the most saline or sodic portions of the fields. After harvest, comparative soil samples indicated reduced soil EC levels and lower sodium, SAR, and ESP numbers. Other studies that have been sponsored by Horizon Ag™ have involved the use of the COMPOSE™ liquid product, applied to the soil directly on or under the seed, then water-run with the irrigation water. Growth and yield increases have been consistently measured in response to such applications. We are currently compiling these studies for presentation in another document. 

Modes of Action

Our studies lead us to conclude that there are three primary modes of action involved with our products and salt remediation. Binding Soil Particles Together for Better Soil Structure: Organic acids derived from humus act as glue to bind individual soil particles (especially clays) together into ideal, crumb sized aggregates2,4. This improves soil aeration and the stability of these aggregates under the motions of wind and water11. Humic substances stick to soils through various means: water, sugars, hydrophobic moieties on the humic molecules, and most importantly, calcium16. Reducing the Osmotic Potential of Salts: The osmotic pull of a salt only occurs if the salt exists in an ionized state. The degree of ionization depends on which anion the salt cation is associated with. When sodium is accompanied by chloride or nitrate the osmotic potential is very high. The fertilizer salt index is an objective measure of this potential to dessicate plants through its osmotic pull on pure root water. When sodium (or another salt) is attached to a humic colloid sized molecule the salt index (osmotic pull) is reduced to less than one-hundredth the salt index. Table 1 below shows the results of a study conducted at a certified agricultural laboratory showing the salt indices of various 0.1 normal sodium solutions associated with various anions.

Measured salt index of various sodium solutions

Selectivity of Active Uptake Mechanisms: Sodium is a specific salt ion that can be toxic to various plants. Plants vary in their sensitivity to sodium. Sodium and potassium are both taken up actively by plants through active uptake mechanisms. In fact, the uptake sites appear to be the same, and in mineral soils, most plant species cannot distinguish between potassium and sodium. The dominant salt is typically taken up in the greatest quantities and if it is sodium specific ion toxicity, symptoms for sodium appear and yield losses occur.

When exposed to organic acids derived from humus, plants take up increased amounts of potassium and lesser amounts of sodium7. The exact mechanism is not known, but it is believed to be tied to well defined trans-membrane proteins. Certain organic acids from humus fractions seem to change the conformation of the trans-membrane proteins that move potassium and sodium through the cell membrane into the cell. This allows the plant to selectively take up potassium while leaving the sodium outside. 

Effects on Plant-Water Relations

Certain low molecular weight organic acids from humus9 included in the our soluble humus products help plants regulatethe opening and closing of stomates in response to moisture stress18. This allows plants to conserve moisture during periods of moisture shortages. Arid areas of the US have both a shortage of rainfall, and an excess of salts. Some of thebenefits we have observed from our products are linked to the plant-water relation effects of the low-molecularweight organic acids in the products. We have several well documented studies that show reductions in water use by fifteenpercent after a few seasons of product use17.

Effects of Heat Stress

Recently published studies at Virginia Tech indicate that some of the organic acids from humus help plants tolerate heat induced stress. Polyphenolic functional groups (a component of humus-derived organic acids) act as electron-receptors (anti-oxidants) to minimize the damaging effects of heat stress. Saline soils and waters are usually associated with hot, dry climates. Some of the damage to plants from salinity are due to the plants’ inability to cool itself off through transpiration. The canopy temperature therefore rises above the critical level and heat stress is unnecessarily induced.

Product Rates and Methods of Application

For saline and sodic soils the most economical treatment is a broadcast application of COMPOSE™ DC granular. It can be applied alone or with soil amendments or fertilizers. Rates will vary from 40 to 150 lbs/acre depending on the severity of the problem. Rates should be based on soil EC, sodium, SAR, and ESP. In precision agriculture, COMPOSE™ DC can be variable rate applied along with soil sulfur according to the salinity or sodium content of the soil.

The liquid product COMPOSE™ is an organic acids concentrate applied in banded soil fertilizers or injected into irrigation water. In soil applied fertilizers it can be applied at 1 to 3 gallons per acre depending on fertilizer rates. In irrigation water, it can be injected at ¼ to 2 gallons per acre-foot of water, depending on the quality of the irrigation water. 

Compose™ Sodium Reclamation

Scientific Background Information Regarding Remediation of Saline/Sodic Soils With Plant Health Technologies™ COMPOSE™ Products

References Cited
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