The Benefits of using Humic Substances in Alkaline Soil Conditions

Posted by Luke Serbina

Dec 21, 2017 9:19:31 AM

canstockphoto25994026.jpg

With soil pH being one of the primary drivers of fertility levels and crop performance, understanding how to mitigate those effects in commercial production has significant value. Here is a brief synopsis of some of the challenges with soil alkalinity and how soil carbon products can provide economic solutions.

What is Alkaline Soil?

pH is the base 10 logarithmic scale used to measure the concentration of hydrogen ions. When a soils pH is above 7 it is termed to be alkaline. A soil with a pH of 8 would be ten times more alkaline than a pH of 7. Significant differences offer different challenges with nutrient availability.

Phosphorus CHART pH.jpg

Phosphorous compounds are bound to calcium and magnesium under alkaline conditions.

How Does Alkalinity Affect Crop Performance?

Typically in alkaline soil conditions there are issues with less mobile nutrients being bound to insoluble soil parent materials such as alkali earth metals like calcium and magnesium. This renders the phosphoric compounds unavailable to soil water solution and root mass flow uptake.

With phosphorous being one of the most important macronutrients for early season vigor and developing maturity, having it bound severely limits the ability of plants to thrive.  With less vigorous plants, they are subject to increased pressure from soil pathogens, insect damage and environmental conditions.

How can Soil Alkalinity be Mitigated?

An example alkali compound found in soils would be calcium phosphate. This strongly polar molecule is unavailable to be released into soil solution. Humic substances are non-polar and effectively depolarize the calcium phosphate compound which in turn releases the phosphorous available into soil solution and root uptake.

Bulk soil pH conditions took decades to alter, and are difficult to change in a short period of time. Altering pH too rapidly can have negative impacts on soil microbiology (some of those microbes are responsible for solubilizing phosphorous).

However, when targeting the rhizosphere of a plant system, we can alter root / soil particle interfaces effectively altering pH conditions to make phosphorous and other nutrients more available. An example of this would be the in-furrow or seed row placement of humic substances. By having humic materials placed with developing root systems, nutrients are more available and less salt toxic to young sensitive roots systems. This enhances crop performance and ultimately yield.

Black Earth ACTIV80 products can increase phosphorous availability by up to 40%--


  • 1995. Wang, X. J. et al. The Effects of Humic Acids on the Availability of Phosphorous Fertilizers in Alkaline Soils. Soil Use and Management. 11: 99 – 102.

Stabilize Your Soil 

Topics: humic material, alkaline soil, Phosphorus, Phosphorus Uptake, Soil Health, humic acid