Friday, March 9, 2012

Mycorrhizal Effects on Root Growth

Here are a number of scientific abstracts which cover Mycorrhizal effects on plant root growth. Please post a comment if you are interested in finding additional information.


         Juvenile plants of Thymus mastichinaThymus zygisLavandula pedunculataGenista hirsuta, and Cistus ladanifer were transplanted from the field to the greenhouse; the soil used was the same in which they had grown at their natural site. The plants were grown to maturity to determine comparative growth, water status, and mycorrhizal colonization under greenhouse conditions and to determine the influence of drought on the symbiosis. After 24 months, L. pedunculata showed the most developed root system; G. hirsuta showed the lowest root/shoot ratio and the lowest percentage of mycorrhizal colonization. This percentage ranged from 32.0% to 82.4% for G. hirsuta and L. pedunculata, respectively. There was a positive relationship, between root biomass and root/shoot ratio with mycorrhization percentage, and a positive response of water potential to that percentage also occurred. After a moderate drought treatment over 4 weeks, increased mycorrhizal colonization percent and root biomass was related to with decreased plant moisture stress. The ectomycorrhizal symbiosis between C. ladanifer and Laccaria laccata appeared to be more severely affected by hydric stress than the endomycorrhizal symbiosis of the rest of the shrubs. This should be considered when this symbiosis is to be established in Mediterranean regions.

Thursday, March 8, 2012

Success in Arid Arizona

     Arid lands across the globe are being impacted by water shortages that are having grave economic consequences. In the arid west of the United States, this is causing a conflict between cities and agricultural entities which are competing for the same water!   At the same time, arid soils have been compromised due to common management practices and therefore are not functioning at optimum capacity.  As a result, these soils provide relatively low levels of water and nutrition to vegetation. These compromised soils lack or are deficient in Mycorrhizal fungi and Humic substances; both Mycorrhizal fungi and Humic substances greatly increase a soils capacity to hold water and a plant’s ability to uptake nutrients. 

     If we do not restore compromised arid soils, we cannot maximize crop success nor the conservation of water in arid lands of the Western United States, nor anywhere else on the globe.

     Mycorrhizae associate with roots and help improve the uptake of water and mineral nutrients from the soil, particularly during times of drought or when soil pH decreases mineral availability.  “Developing agricultural practices using the fungus as an inoculum could help bring back low-input agriculture and enable cultivation of arid or semi-arid lands because the fungus promotes drought resistance in the plants it colonizes” said Dr. Lammers of New Mexico State University. 

     Humic substances, containing Humic Acids, are complex biologic chemicals, which are prevalent in healthy top soils.  Humic substances are incredibly hydrophilic (water-loving),  they significantly increase a soils Cation Exchange Capacity (CEC) and they contribute to macroaggregate formation.  Combined these benefits convert arid soils, which more than likely are not providing sufficient water nor nutrients, into a soil which provides abundant nutrients and water.  

Below are 2 sets of pictures illustrating success in arid Arizona:

  • The following 3 pictures show an increase in root mass in a Barley crop grown in Arizona. The barley was treated with Humic Acids and inoculated with mycorrhizal spores. The plants with the larger root system are from the treated fields. These photos were taken by the farmer who grew this crop.

Barley on the left treated with MycoMaxima (Mycorrhizae) and TerraPro (Humic Acids)
Barley on the right not treated!

Barley on the left treated with Mycorrhizae.
Barley on the right not treated!

Barley grown in the Arizona desert.

  • The next 2 photos show a successful erosion control project on the median of Highway 93, near Hoover Dam. Notice the lack of vegetation on the untreated hills bordering the highway; this site is brutally hot and dry.  As expected the mix of native wildflowers germinated nicely and is now the greenest place around. The hyper-hydrophilic nature of the Humic Acids, plus the improved water uptake of plants because they’ve been made mycorrhizal, accounts for the instigation of sustainable vegetation.

Erosion Control project on Highway 93 in Arizona

Written by:
Aurora Fabry-Wood
Staff Biologist

Thursday, March 1, 2012

Soil Health: Level 2 - Soil Structure

Soil macroaggregates create a soil structure which is permeable (by air and water) and stable (resistant to compaction and erosion).
  • Soil aggregates result when Mycorrhizal Fungi bind soil particulates together. To be more specific Mycorrhizal hyphae, or filaments, are responsible for increasing a plants overall root mass. These hyphae extend throughout the soils surrounding a plant, and in their search for water and nutrients end up binding soil particles together. As hyphae die and begin to decompose they release Glomalin into soil systems. Glomalin is a glue-like protein which significantly increases aggregate formation, by gluing organic matter to soil particles. This process, of binding Labile carbons (as you recall, organic matter contributes to the Labile Carbon pool) to soil particles, traps these rapidly decomposing carbons in the soil; thereby storing them for future use and preventing these carbons from being released into the atmosphere.  
  • Humic Acids have been shown to increase aggregate formation. Please see Level 2 - Carbon Compounds for a detailed description of Humic Acid's role in aggregate formation.  When Humic Acids combine with clay particles, we get the Humus-Clay Domain where most of the Nutrient holding and water holding capacity of the soil takes place!
  • Once these aggregates have been formed, as a result of both Mycorrhizae and Humic Acids, water and air can easily penetrate the soil. Macroaggregates can also be described as Water Stable Soil Aggregates. The term Water Stable Soil Aggregate can be a bit confusing. First of all, "Water Stable" means that a soil which contains water stable aggregates will not collapse when water enters the system (these aggregates remain in tact during a slake test, which is a measure of the disintegration of soil aggregates when exposed to rapid wetting); as compared to a soil which does not contain these water stable aggregates and will collapse, thereby preventing water from penetrating. Once you have fostered the creation of water stable soil aggregates, water can enter the systems and form small pools in the aggregates. These pools hold moisture, gases, bacterial colonies and labile carbons, all of which increase soil and plant health.
This image shows a macroaggregate (on the left) holding its structure during a slake test. The cylinder on the right does not clearly illustrate how a compacted soil will prevent penetration of water, but it does show how much soil will be lost as water runs off a compacted soil.
  • Tilling of soil will destroy these structures, increase erosion and create soil compaction. Tilling of soil reduces stability, by destroying the structural web created by Mycorrhizal hyphae.  Tilling destroys worms passages and other structural spaces created by soil organisms. Worm passages are tunnels which help the soil breath, by letting in water and oxygen and releasing other gases. 
  • Please see No Till and Water for interesting information on this topic.
Written by:
Aurora Fabry-Wood
Staff Biologist