Smart paddock sampling and zone based decisions

Sampling right so your data works hard

Soil testing only pays when the samples match the way the paddock behaves. Zone based sampling gives you clean data for clean decisions. You get fewer mixed signals, fewer average numbers, and better placement of fertiliser and amendments.

How to define zones

• Use grower knowledge first. Mark out soil type breaks, problem patches and historic sweet spots
• Add yield maps, EM38, satellite NDVI or elevation if available
• Limit each zone to a single soil type and similar yield potential
• Aim for two to five zones per paddock to keep it practical

Depths and numbers that hold up

• For grains, common layers are 0 to 10, 10 to 30 and 30 to 60 cm
• Take 15 to 20 cores per zone for a reliable composite
• Keep core counts and depths consistent year to year for trend value

Field workflow

1. Plan the run. Pick paddocks, zones and access points.
2. Sample correctly. Avoid headlands, stock camps and wet depressions.
3. Label well. Include grower name, paddock, zone, depth and date.
4. Handle samples. Keep cool where ammonium or nitrate stability matters.
5. Freight fast. Use the lab’s preferred packaging and forms.
6. Log GPS so you can repeat exactly next time.

Turning lab numbers into paddock decisions

• Budget nitrogen by zone based on mineral N and yield target
• Set phosphorus plans using Colwell P with PBI for that soil type
• Allocate lime where pH is low, prioritising zones that constrain the system most
• Generate variable rate files for seeders or spreaders where equipment allows
• Keep a simple table of spend per zone and track the return at harvest

Common mistakes to avoid

• Sampling a zone that mixes soil types
• Changing core depth mid project
• Too few cores which leads to noisy data
• Waiting too long to get samples to the lab
• Not recording GPS and ending up with different areas next year

Record keeping that saves money

Create a single page per paddock with zone maps, lab results, recommendations and actual applications. Add harvest notes on yield and quality. This becomes the reference that improves decisions every season.

Book a zone based soil testing run with Dawson Ag. We will design zones with you, sample to depth and convert results into a clear plan with optional variable rate files.