Irrigation checklist to reduce run-off this summer

It’s that time again when some crops and pastures start to need irrigation. Environment Canterbury Land Management Advisor, Ian Lyttle, shares a handy checklist for irrigating well.

Good irrigation management is essential to reduce on-farm costs and loss of contaminants to waterways through run-off and leaching. Most annual irrigation maintenance will have been completed by now and the irrigators ready to do their job.

Opportunity abounds in Canterbury to improve on-farm irrigation practices to Good Management Practice (GMP) levels and to make a real difference to nutrient losses off the farm.

Here is a checklist that will help bring practice to GMP if it is not already there!

Before you start

  • Check soil temperatures. Do not irrigate where the temperature is below 10ºc. Grass growth is slow below this point and water will cool soil temperatures more.
  • Check soil moisture status as well
  • Check your weather forecast – no point irrigating if good rain is on the way.

Make good in-season decisions

  • Make good irrigation decisions based on good information. You need this information from soil moisture monitoring, rainfall and PET (potential evapotranspiration) forecasts and pasture/crop water needs.
  • Start irrigating before crops get to stress points and never put on so much that you exceed field capacity – aim for 90% of field capacity.
  • Apply water when the plant needs it to maximise plant growth (remember no matter how much water, plants do not grow in cold soils)
  • Check if you are on water restrictions to avoid compliance issues
  • Make sure your rate of application does not result in ponding or run-off, especially where effluent is applied. If it does, you are putting too much on
  • Graze in advance of the irrigator to reduce soil compaction- stock hoofs compact wet soils. It is a good idea to take a spade with you during the season to check on soil compaction
  •  Adjust application rate or turn off irrigator where rain is forecast
  •  Are you recording your irrigation data and decisions for when your auditor arrives?

Check how well the equipment is operating

  • How uniform is your water application? Use a bucket test to check rate of application and distribution uniformity
  • Does your water meter, pivot control and bucket test all agree on application rate?
  • How effective is your rate of application – is it infiltrating into the soil, ponding or running off?
  • Are you able to control your system so that you do not put on more water than the soil can hold?  This is more challenging for k-line and guns.

If you need more help managing your irrigation, you can get in touch with a Land Management Advisor at Environment Canterbury by calling 0800 324 636 or contact industry body Irrigation NZ.