Month: December 2021

Construction and mine sites are hot spots for disturbed soils – and a significant disturbance can alter the structure of soil entirely, leaving it unfit for purpose.

In Australia, disturbed soils are particularly prone to high concentrations of sodium, a condition known as sodicity, which can create significant structural and revegetative challenges.

Soil disturbances often require holistic solutions, hence the value of microbes. These microorganisms decompose organic matter and fertilise the soil to restore its natural balance and counteract the effects of excess sodium.

In the interest of supporting healthy soil systems and growth, the relationship between soil sodicity, plants and microbes is worth exploring.

What is sodicity?

Sodicity in soil is the presence of a high proportion of exchangeable sodium. Generally, soils defined as sodic have an exchangeable sodium percentage (ESP) of 15% or higher. This influences the physical and chemical properties of soil, affecting the soil’s structure and its behaviour under natural conditions. As a result, soil is more susceptible to mineral imbalances that lead to a range of problems:

• Erosion: soil is eroded away by wind or water
• Slaking: soil structure breaks down upon wetting
• Dispersion: clay particles separate in wet or moist soil
• Surface crusting: water recedes into the soil, causing clay particles to filter to the surface and form a hard crust on top
• Rill and tunnel erosion: water flows through soil, creating a shallow channel
• Hydrophobicity: soils repel water, causing it to bead on the surface and increasing water runoff and erosion. This results in lower rates of seed strike and plant establishment, and it is plants and soil health that solve the problem long-term.

What causes sodicity in soil?

Sodicity is common in disturbed soils because sodic soils typically form in the subsoil layer at various depths, depending on the landscape type and parent rock material. These subsoils are subsequently exposed during the earthworks stage of construction.

When trees and plants are removed during earthworks, the water table can rise, reintroducing soluble salts to the topsoil layer that the plants and soil biology were managing. As water evaporates from the newly exposed soil layer, salts migrate towards the soil surface. Then, when it rains and the soil is able to freely absorb water, soluble salts can be released and flushed deeper into the soil profile, allowing the cycle to begin again. The chemical makeup of the soil can, of course, have a positive or negative effect on this natural process.

What is the relationship between microbes and sodicity?

Microbes naturally counteract sodicity in soil through their symbiotic relationship with plants. Plants and microbes enable each other to grow and thrive, even in the most challenging of soils – but of course, there are levels of sodicity that the natural system may not be able to overcome.

Most microbial species can tolerate soluble salts when they form in water as part of the soil solution, but when evaporation dries the soil, the salts crystallise, causing dehydration. This process induces lower microbial activity in the soil, negatively affecting the soil microbiome and the plant symbioses and delaying healthy plant growth.

This is where soil conditioning becomes important, kicking the natural system into gear. The BioGrowth™ program is designed to prime soil conditions for plants and microbes so that they can thrive and overcome soil imbalances in a more holistic and natural way.

What is the remedy for sodicity?

Implementing the correct soil biology inoculation and remediation program is the most natural and effective way to remedy sodicity in soils. This process involves first assessing the factors affecting soil quality – including levels of exchangeable minerals such as sodium, dispersion, slaking and total soluble salt – and then implementing a plan to address these factors. Typically, Gypsum is used to break sodium particles away from clay particles so that they can be flushed out of the soil profile with water, which is not always a practical solution to the problem.

An effective soil remediation process can be activated within three weeks, and should be monitored and measured until the desired outcome is achieved. Soil reconditioning and fertility enhancement is an ongoing process involving regenerative self-sustaining systems which can take several years to stabilise depending on climatic conditions.

How does the BioGrowth™ program counteract sodicity?

The BioGrowth™ program is unique in that it uses microbes and the symbiotic relationship they have with plants to neutralise sodium and remove it from the plants’ rhizosphere. The process begins with a comprehensive assessment of the soil via laboratory testing to determine sodium levels and other nutrient imbalances. The program works in stages – first cultivating and preparing soils for moisture infiltration and preservation, and then implementing a program with tailor-made soil conditioners like Calcium Plus and Carbon Plus in combination with our Bio-Fertiliser, a natural mineral ore-based microbial inoculated fertiliser.

A typical program involves the application of ameliorants followed by soil cultivation to enhance the effect of soil conditioners and allow moisture penetration. The cultivation process is critical in preventing a hard surface layer from forming, sealing out moisture and rendering soil conditioning processes ineffective.

Once there is a sufficient concentration of water in soil, microbe activation and seed germination can occur. During initial stages of growth, the microbes protect the establishing root system from sodium and other imbalances in the soil. Then, as the plant establishes and forms leaf matter, the microbes and the plant are able to work together to flush sodium out by transpiring it through the leaves – similar to the way humans sweat.

When implemented effectively, the BioGrowth™ program can condition unbalanced, high-sodium soils with sufficient nutrient content to allow microbes to survive and plants to thrive long-term.

Are sodic soils onsite interrupting a project or thwarting your revegetation efforts? Contact our soil science experts today for a holistic, long-term solution.

 

Growing vegetation on sloped land can be challenging, particularly without the correct preparations in place. 

The successful revegetation of a slope requires an understanding of several factors influencing soil quality and stability, both of which are key to successful vegetation establishment with or without topsoil placement 

The gradient and length of the slope ultimately determine whether it will be possible to apply topsoil and ameliorate the subsoil effectively.

Revegetation projects are inherently complex when attempting to establish vegetation and stop erosion on steep and long slopes. Water runoff in particular needs to be controlled and incorrectly prepared slopes that do not focus on slowing water flow down are at particular risk of failure. 

As a rule, graded smooth cut compacted areas are very slow to establish vegetation at any gradient, putting them at greater risk of failure. 

In order to stabilise the topsoil layer, all gradients should be roughened via track rolling, horizontal ripping or pin wheeling before seeding. This slows water flow, reduces water runoff and increases water absorption into the soil layer beneath the hydromulch, allowing vegetation to thrive with less frequent watering. Short and long-term, this improves slope stability and significantly enhances vegetation growth.

Processes like track walking, horizontal ripping and pin wheeling strengthen the bond between the topsoil layer and the subsoil below it, minimising slumping and rilling of the soil surface layer to optimise stability. These processes create a surface which is better for binding, allowing the binders in the hydromulch layer to hold onto the soil. 

A process like back-blading delivers much smoother results, and although these results look nice, they work against the revegetation process by minimising water penetration and increasing water flow. The resulting erosion and rill formation due to the impact of rain and increased overland flow rates makes it difficult for EnviroStraw BFM hydromulch to deliver the intended results. 

Watch the video below to see the results for yourself.

Are you preparing to revegetate a slope with a steep gradient? Contact our revegetation experts for professional advice that guarantees results.

 

pH is only one of several factors that determine soil and plant health, but left unidentified, it could be seriously detrimental to your revegetation efforts.  

Studies show that soil pH varies widely by location across Australia, affected by factors such as leaching and the presence of vegetation and basic rocks, all of which can have a significant impact on soil quality. While addressing pH is critical, many worksites find that their workflow does not allow sufficient time for a soil conditioning program, leading to revegetation failures. 

Are you concerned about the impact of pH levels on your site soils? If so, read on to find out more about understanding, testing and correcting soil pH levels. 

Defining soil pH

Soil pH is a measurement of the acidity or alkalinity in a soil. pH is defined as the negative logarithm of the activity of hydronium ions in a solution. In water, it normally ranges from -1 to 14, with 7 being neutral.

There are two common testing methods for soil pH:

• Using a pH testing kit.
  These can be purchased from local hardware supply stores.
• Sending soil samples to a laboratory.
  For optimum data scope and quality, it’s best to send soil samples to a NATA-approved lab. This option also allows for a wide range of soil characteristics and mineral concentrations to be tested. 

A soil pH between 6.4 and 7.4 indicates optimum availability of water-soluble nutrient minerals for plant root uptake. However, this also indicates that these minerals are most susceptible to volatilisation and most likely to react with each other and/or leach out of the soil profile. The more the soil pH deviates from this optimum range, the more these reactions take place and the less available they are for plant root uptake. This phenomenon explains why it’s so important to balance soil pH with soil conditioners in conventional farming systems. 

Understanding soil conditioners 

Soil conditioners are important components of maintenance and fertilisation programs – and the most appropriate soil conditioner depends on the soil analysis. Low soil pH levels can be conditioned with lime and dolomite, while high levels are typically conditioned with Gypsum, iron sulphate and other sulphate-based fertilisers. 

The BioGrowth™ system applies these same minerals in non-water soluble form, meaning soil pH and associated chemical reactions, volatilization and leaching factors are not at play. Therefore, soil pH is essentially irrelevant. The soil biology species mine for these nutrient minerals as a source of energy and simultaneously exchange them with plants for root exudates if and when required.

The use of soil conditioners like lime dolomite and Gypsum in water-soluble fertiliser systems is critical, and even more so during periods of intense rainfall due to the excess leaching of nutrients. This process can cause plant nutrient deficiencies and induce conditions that lower soil pH. 

 

Measuring total mineral levels is important to ensure that suitable levels of each mineral are available once the soil biology system reaches peak performance. The following soil pH chart shows the plant-available nutrient (water-soluble) levels at various soil pH levels.

Correcting soil pH 

While the principles and practices of the BioGrowth™ system don’t recommend specifically correcting soil pH, they do recommend soil conditioners that address mineral deficiencies developed under specific climatic conditions. 

The correct process for adjusting soil pH levels depends on two factors: 

• Test results
  In conventional farming systems, lime and dolomite are commonly used to correct low soil pH levels. Common treatments for high soil pH include Gypsum and iron sulphate and/or acidifying water soluble fertilisers.
• Soil texture class
  Soil texture can alter the effect of applied soil conditioners significantly. pH will increase more in sandy soils with low buffer capacity than in clay soils. For example, applying one ton of high-quality lime may increase a sandy soil pH by 0.3 and a clay soil by only 0.15.

In the roading, construction and mining industries, these same soil conditioners are also used to enhance physical characteristics of soil like stability, resulting in a more dense, compacted soil post-earthworks. 

Like any other soil conditioner, Calcium Plus (and Carbon Plus, to a lesser extent) may impact soil pH if applied at well above recommended rates. However, these products are primarily designed to supply missing minerals rather than to alter soil pH. 

Common pH misunderstanding

Excessive use of soil conditioners is one of the most common challenges when it comes to correcting soil pH – particularly in the revegetation industry. Applying large amounts of soil conditioners is not conducive to timely, long-term stabilisation of reclaimed land after major earthworks. While this may enhance some soil characteristics, such as stability and structure, it may also induce mineral imbalances and nutrient lock up constraints that affect vegetation establishment post-conditioning. 

The BioGrowth™ program approach is different in that it is designed to work with nature in a more holistic and natural way. This approach targets soil microbiology development based on an assessment of the soil and climatic conditions. Most importantly, the recovery and stabilisation process is driven not by soil conditions but by the symbiosis between soil biology species and selected plant species. 

When did you last have your onsite pH levels tested? If your site soils are due for a checkup or a mineral adjustment, reach out to our soil scientists and find out how BioGrowth™ could help.