A practical way to assess your soil

It is important for farmers to know the health of their soil, because it has an impact on almost every aspect of a farming practice. There is an interesting book – Visual Soil Assessment by Graham Shepherd – which I think can be of great use for farmers to get an idea of their soil health. Farmers are reliant on healthy soils as a medium for the growth of high quality feed (e.g. ryegrass pastures, oats, maize and sorghum, to name just a few). Soil health relates to the effective functioning of a balanced range of different soil micro-organisms that are able to break down organic matter and cycle nutrients. A healthy soil has good structure, is well aerated and has the right set of nutrients that are in balance and available to plants and /or soil micro-organisms for uptake. Having a healthy soil makes it possible to reduce fertiliser costs and chemical herbicide and pesticide control. It will also reduce the need for physical actions on the farm such as ripping.

Deterioration in soil health is associated with negative impacts on pasture and crop production and quality, negative impacts on animal health, increased production costs, increase nutrient losses, greater greenhouse gas emissions and decreased carbon sequestration. It is important for you as the farmer to evaluate your soil in order to assess its health for yourself.

There are many ways in which soil health can be assessed, but many of them are time-consuming and require the services of professionals such as soil scientists, fertiliser reps and agricultural consultants. There are alternative, cost-effective methods that can be carried out in the field. These methods help farmers to visually evaluate the quality of the soils under different crops or pastures. It should be noted that such a visual soil assessment should never replace taking soil samples and having them comprehensively analysed. Using the two methods in conjunction creates a powerful tool to manage and identify opportunities to improve soil health. The health of the soil may be improved by improving the following soil properties that can be used in the visual soil assessment of your farm. Visual Soil Assessment by Graham Shepherd is a useful field guide to a few soil physical properties, which will be discussed below.

Soil texture

Texture can be used to determine what type of soil you have, as it is important to manage different soil types in different manners. Texture cannot be changed, but it relates to many soil properties relating to healthy soils so it is important to take note of the texture. For example a soil with more clay can hold nutrients better, but require a different irrigation approach than a sandy soil with poor nutrient holding capacity and a higher irrigation demand.

Soil structure

Structure refers to the proportion of small and large pieces of the soil, which are called fine aggregates and larger clods respectively, and can be seen in figure 2. It is important to take note of the structure as it influences the ability of the soil to hold water and nutrients and the ease at which roots can move in the soil to find the necessary plant nutrients and water