Soil and Irrigation Management

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How do I measure soil quality?

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Choosing a Moisture Monitoring System

1. Which provider should I go with?

Look for someone who offers good support, not just good hardware. A probe is only useful if you understand the information coming off it, so make sure the provider can help with setup, interpretation, and ongoing advice.

2. What sort of logging or telemetry system do I need?

Check what connectivity you actually have on-farm - mobile coverage, Wi-Fi, Bluetooth, radio networks. If coverage is patchy, ask what alternatives they can offer. Reliable data flow is more important than fancy features.

3. Are there extra costs I should know about?

Yes. Most systems come with annual subscription or support fees. Get a clear picture of all ongoing costs before you commit, not just the upfront price of the probe.

4. Should I stick with a standalone probe or set up a full network?

Some platforms can pull in data from different brands, which is handy if you already have gear. A farm-wide network gives better overall coverage, but a single well-placed probe may be enough in some situations.

5. When and where should I install the probe?

Earlier in the season is usually better - soils are moist and you get a cleaner baseline. Most probes need a decent rainfall event (around 30 mm) before the SMD data settles down. Choose a representative spot considering soil type, irrigation uniformity, and what you’re trying to monitor.

6. Why do prices vary so much between companies?

Sensor quality and durability are the big reasons. Some sensors perform much better in challenging soils such as gravels or very stony profiles. Cheaper sensors may work fine in uniform soils but struggle elsewhere.

7. How do I know if the probe is set up properly, and how do I use the data?

Make sure Field Capacity and Stress Points are set sensibly for your soil. Keep an eye on the data - if the graph doesn’t respond to rain or irrigation the way you’d expect, something’s off.

If you have multiple depths, use the sum of the sensors rather than the average; it gives a truer picture of what’s happening through the profile.

8. Where can I find more reliable information?

Irrigation New Zealand’s soil moisture monitoring booklet is an excellent starting point. Other useful tools include:

Irrigation Glossary (INZ)

S-Maps (Landcare Research)

Moisture Probe and Sensor Options

There are plenty of sensor types: capacitance, TDR, tapes, single-depth or multi-depth. Each has pros and cons depending on soil type and how much detail you want.

Be mindful of installation - clay and gravel soils need extra care to reduce soil disturbance around the sensor.

Useful metrics to monitor:

Individual depth traces

Root-zone sum

Full and refill points

SMD

Soil temperature

Linking Soil Probes with Weather Information

Your probe data becomes much more useful when combined with local weather information. Soil temperature (particularly at 10 cm) and hourly moisture changes help you time irrigation and fertiliser.

Before applying N, check the forecast - dry soil and dry weather mean poor responses and higher losses. The FAR weather platform is a good reference point for this.

Precision Agriculture & Managing Variability

Crops rarely perform evenly across a paddock. Start by identifying the consistently high and low performing areas - simple observations go a long way.

As you build confidence, you can start shifting towards variable rate applications (“feed to the need”).

Tools that can help:

FAR N-Calculator

N-Sight

Sirius Wheat Calculator

Quick N

AmaizeN Lite

Mapping options such as drones, satellites, EM surveys and yield maps can support this, but ground-truthing with crop walks is still essential.

Irrigation Best Practice

Regular bucket testing and system checks help make sure your irrigation is actually delivering what you think it is.

For VRI systems, EM mapping and soil information can help refine application zones.

Probe data is most powerful when used alongside irrigation performance data.

Soil Nitrogen & Residue FAQs

Will I “mine” my soil nitrogen if I rely on soil N tests?

No. Soil microbes continue to break down organic matter regardless. Keeping good levels of residue and plant material in the system is what maintains soil organic matter over time.

Does cereal straw tie up nitrogen? What about legumes?

Cereal straw can temporarily immobilise N as it breaks down. Legume residues generally release N more quickly. The N-Sight tool can help estimate N release from different residue types.

Is liquid N more efficient than granules?

Not by itself. What improves efficiency is applying N in smaller, more frequent doses — if a liquid system makes that easier, then yes, it can improve efficiency indirectly

Moisture Monitoring & Irrigation – Quick Guide

1. Choosing a Provider

• Go with someone who offers good support and can help interpret your data.
• A probe is only useful if you understand what it’s telling you.

2. Telemetry & Connectivity

• Check what coverage you’ve actually got: cell, Wi-Fi, Bluetooth, radio.
• If coverage is patchy, ask the provider what workarounds they offer.
• Reliable data flow is more important than fancy features.

3. Costs to Expect

• Hardware is only part of the cost.
• Ask about annual fees, data subscriptions, and support charges.
• Get the full cost upfront.

4. Standalone vs Whole-Farm Network

• A single well-placed probe may be enough.
• If you already have sensors, check if they can be integrated into one platform.
• Networks cost more but give better coverage across different soil types.

5. Installing the Probe

• Install early in the season when soils are naturally moist.
• Probes usually need ~30 mm of rain to settle in and give good SMD data.
• Place them in areas representative of your soil and irrigation, not in extremes.

6. Sensor Quality

• Price differences usually come down to sensor accuracy and durability.
• Better sensors perform more reliably in gravel, stones, and variable soils.

7. Checking Your Probe Is Working

• Make sure Field Capacity and Stress Points are set correctly for your soil.
• Check the graph responds properly to rainfall and irrigation.
• If you have multiple depths, look at the sum through the profile - not the average.

8. Using Weather Info

• Soil temperature (especially around 10 cm) helps time irrigation and fertiliser.
• Combine probe data with local weather forecasts or the FAR weather platform.
• Before applying N, check rainfall - crops won’t respond well on dry soils.

9. Precision Ag Starter Tips

• Note where crops consistently grow better or worse inside a paddock.
• “Feed to the need” - reduce inputs where crop demand is lower.
• Tools that help: FAR N-Calc, N-Sight, Sirius, Quick N, AmaizeN Lite.

10. Common Soil N Questions

• “Will I mine my soil if I rely on soil N?”
  No. SOM breaks down regardless - keep good residue levels to maintain it.
• “Does straw tie up N?”
  Cereal straw can temporarily. Legume residue releases N faster.
• “Is liquid N more efficient?”
  Not by itself. Smaller, more frequent applications (liquid or granular) are more efficient.

11. Sensors & What to Watch

• Sensor types: TDR, capacitance, tapes, single vs multi-depth.
• Installation matters - take extra care in clay or gravel.
• Key metrics:
  • Individual depth traces
  • Root-zone sum
  • Full & refill points
  • SMD
  • Soil temperature