Good quality soil is essential to the success of revegetation. Without fertile, nutritious soil, any efforts made to successfully germinate vegetation will be in vain, whether it is a smaller scale home garden or a larger scale civil project. In short, soil provides the necessary food, water and oxygen that is needed by plants to support healthy growth and development of seeds, so it is important to ensure that soil is of good quality.
Soil Types as Growing Mediums
The type of soil plays a large role in determining how well seeds will germinate. Soil can be judged by five types; sandy, silty, clay, loan or chalky. Each of these varieties has its own characteristics which can be improved in different ways depending on their needs. For example, sandy soils don’t retain nutrients well so it needs to be complimented with an organic matter such as fertilizer or mulch.
The most commonly found soils are silty and loan which are regarded as the best type of soil for growing vegetation as they usually need less work. In some cases, the soil needs to be raked, also known as scouring, to ensure that the soil is loose to encourage and support rapid growth or topsoil may be applied on top of the existing soil. Clay soils are a lot more problematic. Although they are full of nutrients, clay lacks aeration creating very little oxygen for plant roots to access, while the fine particles mean that plant roots are unable to penetrate the space between them to grow healthy grass.
Chalky soil is one of the worst soil textures for cultivation and revegetation due to its naturally high alkaline properties that cause mineral deficiencies in the soil. In order to reverse this and increase the quality of the soil is to add organic matters in the form of mulches, fibres, fertilizers and added nutrients such as calcium.
The Chemistry of the Soil
Cation exchange capacity (CEC) is the measure of the soils ability to hold positively charged ions. It is an important soil property that influences the soil structures stability, nutrients availability, soil pH and the reaction of the soil to fertiliser and ameliorants. The organic and clay mineral matter components of soil have negatively charges sites on their surface which hold and absorb positively charged ions (cations) by electric force. This is critical to the supply nutrients that vegetation receives because they exist as cations, for example magnesium, potassium and calcium. In general terms, soils with large quantities of negative charge are more fertile because they retain more cations, such as clay soil.
pH scale describes the acid/alkaline reaction in soils. Most plants prefer a neutral soil, but some prefer slightly acid or alkaline conditions. Soil pH affects plant growth directly as it determines the availability of nutrients needed to support growth. Soils with a pH of 7 are identified as neutral. pH’s within a range of 0 – 6.9 as defined as acidic, and a pH between 7.1-10 is considered alkaline. Plant growth and soil processes are favoured by a soil pH range of around 5.5 – 8.
In a recent project that was undertaken by Spray Grass Australia, stockpiles were thought to be high in sodium due to the surrounding environment. An adequate soil test and analysis was conducted to determine the state of the soil and if any amendments were required to reduce the salinity. Results found that the soil was moderately to strongly alkaline and high in saline and chlorides, but also was high is Sulphur. Sulphur is usually utilised to treat soils that are alkaline, but because the soil was high in Sulphur, it would not treat the soil as needed.
The founding showed that there was an obvious problem with excess salts in the soil which would severely limit the establishment of grass. A high application of gypsum to the stockpiles was the recommendation by Spray Grass Australia. Gypsum acted as a calcium source for the soil which was used to enable the clearance of Na+ (sodium) ions to allow for the long term survival of vegetation that was going to be introduced through hydromulching works. Furthermore, an acidic fertiliser was utilised to enrich the soil with the essential nutrients of phosphorus and nitrogen
Feeding Your Soil for Growth
Soil is a breathing organism that needs feeding and watering and they are the building blocks that vegetation needs as well for healthy and successful growth. There are three important nutrients that plants require from soils, without any which one they could not survive, and are referred to as the primary macronutrients: Nitrogen (N), Phosphorus (P), and Potassium (K). Often, soils lack these nutrients, either naturally or as a result of environmental factors or over cultivation. Soil lacking in nutrients require them to be supplemented in order to create the ideal environment and encourage growth, this is most often done in the form of NPK fertiliser which is commonly added to hydroseeding and hydromulching solutions.
Nitrogen (N) – Nitrogen is largely responsible for the growth of leaves on plants and provides the Vital to chlorophyll for photosynthesis.
Phosphorus (P) – Phosphorus is responsible for root growth and flower development and aids in the structural strength and quality of crop and seed production.
Potassium (K) – Potassium is the nutrient that helps the overall functions of the vegetation perform correctly and contributes to the overall growth and development.
Before conducting revegetation works, a soil test and analysis should always be undertaken to ensure the stability and quality of the soil to ensure that optimum growth is achieved.