Sodic soils are very common around Australia, particularly in Queensland where 45% of soil is considered sodic. Here, we look at what sodic soil is, why it causes major headaches in many industries, and what can be done about it.
Soil is composed of a combination of clay, sand and silt in varying proportions. These components have a negative charge. In addition, elements like calcium, sodium and magnesium may be present within the soil. They have a positive charge and are known as cations, meaning they can bind themselves to the soil particles. It is this combination of particles and cations which gives soil its structure.
Sodic soil is soil that holds sodium in high proportions. In this soil type, the proportion of sodium will be high relative to other cations (atoms with a positive charge). Sodic soil occurs when sodium leaches into the soil over time and a higher volume of sodium binds itself to clay particles. This displaces other cations.
This process will eventually begin to affect the soil structure. Clay swells when wet because of the sodium present which forces the clay particles apart. The bonds between soil particles are weakening, meaning there is potential for erosion and other issues.
Sodic soil causes numerous problems, particularly the following:
Sodic soils are vulnerable to subsoil dispersion. This is when clay particles are overwhelmed by sodium, which means the soil breaks down and washes away. Erosion can happen quickly, with gullies and tunnels appearing.
Dispersion can also occur on the soil surface. Here, it causes a crust that prevents water infiltration.
Sodic soil destroys aggregation, leading to dense, cloddy soils. Water and air movement are impeded, which causes severe structural problems and potential collapse.
Sodic soils cause problems for any industry that uses or disturbs the soil, so included are farming and agriculture through to road construction and mining.
Agricultural activities are particularly affected by the crusting that occurs with sodic soils. Many seeds are crust-sensitive so germination is impeded. Water runoff from crusted soils is also a problem because more frequent irrigation is required. The runoff also takes with it fertilizers and pesticides.
Stable soil is vital for construction and particularly for infrastructure construction. Road surfaces create a lot of runoff, so it is vital that the soil is stable to cope with this. For roads to stay in good condition for longer, the soil in the area must stay structurally sound.
In mining, it is also crucial that the soil is kept as stable as possible for safety reasons. Many activities related to mining, such as digging and road construction, interfere greatly with the natural drainage of the soil in the area. This kind of disturbance in sodic areas is very likely to cause erosion and silting. Given the large expanses of area affected by mining activities, sodic soil can be a major problem.
Where sodic soil is already causing problems, or is likely to, there are a few methods that could be used to cope.
Many of these methods rely on capturing sediment in structures like silt fences, sedimentation ponds and check dams. These cannot really be considered a solution to the problem. They do not address the cause of the problem, but instead manage the symptoms. They are costly to install and require frequent maintenance.
A method of sodic soil control can only be considered a solution if it keeps the soil in place. Is this solution available? Yes, erosion and sediment control devices do exist that can take care of sodic soil.
These are all-in-one solutions that are applied directly to the soil surface. Here’s a little more on how they work.
These products are designed to keep the soil in exactly the place you want it. They are spray-on solutions that permeate the surface of the soil. The product binds itself to underlying material which enables a strong, stable and durable surface to form.
This layer now protects the soil structure from water and wind erosion and suppresses dust. However, it does not impede seed and vegetation growth, nor does it cause water to run off. In fact, there is likely to be less runoff compared to untreated sodic soil.
Spray-on erosion control products are liquid polymers. The product is diluted with water and sprayed on by hand or industrial spraying machinery. The typical lifespan of the product is a minimum of six months with the potential to last up to two years.
The application is simple and safe. The product saves time compared to other erosion control measures and does not require frequent or laborious maintenance. Minimal soil preparation is needed.
The products are also very cost-effective. Because they prevent a large degree of water runoff, water savings of up to 30% can be expected. In agriculture, this is particularly useful. Savings in water cost are compounded by the impact of less fertilizer and pesticide lost to runoff.
Non-toxic and environment-friendly erosion control products are available, meaning this is an ideal solution for most projects. They have been used in the farming and agriculture, mining, construction, military, commercial, government and industrial sectors. Both land and aquatic flora and fauna are not harmed by the use of these products. The product is biodegradable.
Spray-on erosion control products are non-volatile, non-flammable and non-hazardous for safe storage.
The products are waterproof so they are not impacted by adverse weather. Significant rainfall and storms do not affect the performance of the product.
Common applications of these products include cut or embankment batters, preload embankment protection, stockpiles and bunds, V-drains and catch banks.
Spray-on erosion control products present a very easy-to-use and cost-effective solution to sodic soil related problems. They suit a wide range of applications, even those in environmentally sensitive areas.