Background and Objectives

Over the three years prior to 2001 various trials had been funded by MAF and MFE to determine and test "Best Management Guidelines" for Sustainable Irrigation. Once these guidelines were confirmed there was a need to get this management tool out to farmers.

The objectives of this project were, therefore, to:

1. Demonstrate the economic and environmental benefits of using the "Best management guidelines for sustainable irrigated agriculture"
2. Obtain useful data for writing up as case studies to be used for the future
3. Encourage the uptake of the "Best management guidelines for sustainable irrigated agriculture"

Benefits

During the testing stage, one of the farmers noted how much interest there was in his property, once people knew what trials were in place. Every time he or his wife was out in the community, other farmers were always asking him when he was irrigating next. Another comment he made was "During the season he was not irrigating for 100 days when others around him were". He had the information and trusted it, others around him were not so confident. At a cost for irrigation of $200/day, this saved him about $20,000.

1. Community benefit
   Approx 400,000 ha of land in Canterbury is irrigated. Spreading the demonstration sites throughout the region, will maximise the uptake of the management tool. Results will be published in the regional paper weekly during the season on the farming page. Field days run for farmers to give them a hands on introduction.
   
2. Commitment
   Farmers will contribute to the cost of some of the monitoring equipment and read data on a weekly or more frequent basis depending on the season.
   
3. Existing strategies
   This project would be an incremental step towards Part I of a strategy discussed by the regional council and irrigators to establish a telemetry and internet based programme for monitoring soil moisture and making this available to all.
   
4. Sustainability
   Improved irrigation practise has many benefits; less water used, less labour used, less electricity, less fertiliser, healthier soils, and better production. So is good economically and good for the environment.
   
5. Alignment with Government initiatives
   Farming and irrigation are very important to the region. The trial projects to date have determined the right tool. Unless the tool is used by farmers, the investment to date is wasted. Also the project indirectly contributes to the drive towards reducing greenhouse emissions, through efficient use of electricity. The project will encourage efficient use of energy.
   
6. Value for money
   The geographic spread will make it easy for farmers to access the management tool. The same system could eventually be extended throughout NZ. Canterbury is the irrigation centre of NZ. This project is extremely good value for money given the high level of money contributed from farm and industry sources.

Canterbury Soil Moisture Levels and Ground Temperature

Soil moisture and temperature were generally logged every 30 minutes, and results were updated weekly during the irrigation season, otherwise monthly.

Click the highlighted areas for results. This will open a PDF file in new window.

Understanding the Data

View an example graph.

Each monitoring site has two sensors (top and bottom). The bottom sensor is installed flat at about 500 mm below ground level. The top sensor is installed on a slope from ground level to about 400 mm (ie in the root zone).

The depth shown in the graph is the average depth of the top sensor. Each sensor records soil moisture and temperature. The top temperature is recorded at 50 mm below ground level.

The temperature at the top sensor is variable as it is responding to daily changes in air temperature. The temperature at the bottom sensor is a smooth curve as it indicates the storage buffer in the soil.

Soil moisture will be plotted in mm/100 mm. To determine water in soil, take reading from graph, say 35 on the 10th, and multiply by 5 (if average depth (say 250) x2 = 500 divide by 100 = 5). Ie 125 mm water in top 500mm.

Example - How much to apply and how often

To determine water use at the moment.  From the graph on the 8th April, reading was 36.5mm/100mm.  On the 13th April reading was 32 mm/100mm.  The difference is 4.5mm/100mm over the 5 days. ie 4.5 mm/100mm x(250mm / 100 x2)=22.5mm water used over the 5 days, or 4.5mm / day.

If you are able to irrigate your property in 10 days, the net amount you would need to apply is 45mm.  Assuming your system is 75% efficient, you actually need to apply 60mm.

• Alan Street