SFF 05-051: Quantifying losses resulting from surface ponding during irrigation
- The Sustainable Farming Fund
- Horticulture New Zealand - Process Vegetables
- Foundation for Arable Research
- Hawke's Bay Regional Council
Contributing Science Providers
- Page Bloomer Associates
- Hawke's Bay Regional Council
- Centre for Precision Agriculture - Massey University
- Spatial Solutions
Combine soil moisture monitoring, LIDAR topography, ECa mapping and surface flow modelling to answer the question: “Which simple field observations can provide valid indications of the quantity of irrigation lost as a result of surface ponding?”
The project used a range of soil monitoring technologies combined with GPS, GIS and hydrodynamic surfacae flow modelling to assess irrigation infiltration and ponding. Tools included 'Diviner' and TDR soil moisture monitoring, EM38 scanning with RTK-GPS, and Mike21 surface flow modelling. We still want want simple guidelines or ‘rules of thumb', suitable for use in on-farm irrigation efficiency evaluations, without the need for high technology tools.
The biggest problem with simple observations is making them adequately.
While we could assess the extent and duration of surface ponding, (on the surface) we consistently noted little puddling even when application rates were very high. However, when holes were dug to observe the depth of the wetting front, free water from within the soil matrix (from cracks) rapidly flowed into them. This is clear evidence of high rates of preferential flow from surface to soil layer boundary. From this and other work, we believe this to be a very common but unnoticed occurence.
We have identified the likely role of surface roughness, but would need many observations to derive empirical values to use in any situation. We note the use of Mannings 'N' in channel flow, and that we needed to use out of range values to make our modelling provide realistic representations of surface flow.
We had difficulty correlating EM38 data and changes with our other soil moisture change data. We now realise the soil was far too wet when we started, so there was excess wetness over much of the area after irrigation. We also note recent work showing the need to calibrate EM38 away from the affecting soil. Both will have limited our ability to use EM38 to adequately describe changes in soil moisture status resulting from an irrigation event.
- Dan Bloomer, Page Bloomer Associates, Irrigation NZ Board
- John Donkers Deputy Chair INZ, Irrigating Farmer, Dairy Consultant
- Grant Bunting, INZ Board, Manager PGG Irrigation
- Hugh Ritchie, Irrigating Farmer, Federated Farmers, SFF 02-051 Applicant
- Nick Pyke, CEO, Foundation for Arable Research
- Sarah Bromley, Business Manager, Horticulture New Zealand
- Andrew Curtis, Land Management, Hawke's Bay Regional Council
- Project Summary Report 4MB pdf
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- Centre Pivot Irrigator Report 4.3MB pdf
- Centre Pivot Evaluation Report 1 MB pdf