Precision Nutrient Management – Zonal Soil Management

Zonal soil sampling is the process of using your knowledge of historical management and spatial factors to separate a field or management unit into areas of more uniformity for soil sampling than could be achieved by testing the whole paddock.

Zonal sampling takes into consideration things like differences in soil type across an area, differing yield capability, historical fertiliser regimes, cropping history, and other differing management features. If known variability exists and there is information available to delineate these differences then these areas should be sampled separately. Zonal soil sampling uses knowledge of historical management and spatial factors to direct where to take samples to determine if these areas have different fertiliser needs. Tools such as yield maps, crop sensor maps, EM soil maps, aerial imagery etc. provide more information about variability in the field and where soil sampling can help interpret variability.

The process and results:

Patterns showing consistency from one data layer to another – such as multiple years of yield maps, or a yield map and an aerial photo – are more likely related to soils than other sources of variability. In many cases, a soil map or topography map can be a good base for yield map overlay and other sources of spatial information. Experience gained from tillage, cultivation, harvest, and scouting the field can also serve as an effective information layer.

After you’ve pulled information from multiple data layers, including your on-farm knowledge and experience, the field is subdivided into management zones. Look for general categories when subdividing and don’t create lots of subdivisions. Generally three to six zones should be adequate. Excessive subdivision may create small areas which are unable to be efficiently managed. Management zones need not be contiguous – samples may be collected from more than one area of the field that fall into the same range of yield, soil type, etc. making this the same zone.

Summary:

Zonal soil sampling is an effective way of undertaking a more targeted and intensive soil testing regime without incurring a large cost for processing lots of individual soil samples at the lab. To effectively undertake Zonal soil sampling however, spatially variable maps are needed to create a sound basis for creating the soil sampling strategy.

To find out more, click here to download the Zonal Soil Sampling flyer.