Good fertiliser recommendations start in the paddock. Choosing the right soil sample location is just as important as the collection method and laboratory analysis. 

Representative soil sample sites reflect paddock variability. Too few samples, or too many in one area will skew the results with follow-on impacts on the fertiliser recommendations.

Selecting the right number and location of sites within a production zone is critical to understand the nutritional and soil health status of the area and provide an accurate fertiliser recommendation.

There are different strategies for planning your sampling sites, such as grid and transect sampling, but CSBP has found that zone-based sampling gives the best results in the most cost-effective way.

So, what’s the process?

Step 1- Define your production zones
Paddocks are rarely uniform. Analysing and treating good/bad areas separately is important for precise fertiliser recommendations that match paddock and crop needs. CSBP’s DecipherAg biomass imagery and zones tool can help to identify plant growth variability within the paddock and delineate production zones. Yield data, satellite or aerial photos, Electromagnetic (EM) and Gamma Radiometric data can also be used to identify areas that may require different treatments.

Step 2 – Review or select sites
Within CSBP DecipherAg, from the Manage menu, select Manage Sites to create or import new soil sample sites. You can also review existing sites based on zones and archive them if they are no longer representative, or correct the location by moving or merging them. Rules of thumb such as having a site every 30ha (broadacre) can be used as a guide, but the number of sites required will depend on paddock variability. 
Be sure to avoid areas such as livestock camps, headlands, and lime/fertiliser dumps when selecting sites.

Step 3 – Name the sites
Giving a site a name that is meaningful to you makes interpreting sample results easier. Historically, individual letters or numbers have been used to name sites, such as A, B, C etc, but the best practice is to add details that act as a reminder of why that site was selected.

An example may be a reference to the Farm, the Paddock, the site identifier and the management zone it represents.