The Almond Irrigation Best Practice Management project was funded by Hort Innovation, using the almond research and development levy and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.
The project was conducted by the South Australian Research and Development Institute (SARDI), with assistance from the Victorian Department of Jobs, Precincts and Regions (DEDJTR) and Netafim Australia.
- Variation in dripper outlet flow rate across individual valve units was greater than recommended in over 80% of sites evaluated
- Age of dripline was a key contributor to drip system performance
- Frequency of dripline flushing correlated well with drip system performance, and indicated that flushing is generally not carried out often enough
A key component of the project was a drip irrigation system performance audit of the Australian almond industry, to assess the performance of drip irrigation systems across the major almond producing regions of South Eastern Australia (Adelaide Plains, Riverland, Sunraysia and Riverina). In total fifty irrigation valve units were tested across the above regions, and were ranked according to their performance against a set of standard indicators.
Performance of valve units against these indicators was also compared with other data collected at each site, including age of the system, water source, filtration type, and maintenance frequency. These critical factor comparisons assisted in identifying best practice management leading to good drip irrigation performance.
The following set of standard indicators of irrigation performance were used for this project:
- Pressure variation (important for non-pressure compensating emitters):
- Compares the highest and lowest pressures measured across the valve unit, and expresses the difference as percentage above and below the midpoint (average of the highest and lowest pressures);
- The target is less than ±10% variation from the midpoint between the highest and lowest pressures (for example for a midpoint of 100 kPa, the highest pressure should be <110 kPa, and the lowest >90 kPa);
- Flow Variation:
- Compares the highest and lowest emitter flow rates measured across the valve unit, and expresses the difference as percentage above and below the midpoint (average of the highest and lowest flows);
- The target is less than ±5% variation from the midpoint between the highest and lowest flows (for example for a midpoint of 2 L/h, the highest flow should be <2.1 L/h, and the lowest >1.9 L/h);
- Flow variation from quoted (important for pressure compensating emitters):
- Compares the average emitter flow rate to the manufacturer’s quoted flow rate for the dripline being used. For pressure compensating emitters the flow rate should be constant across the valve unit despite variations in pressure, and should be close to the quoted flow rate.
- The target is less than ±5% variation from the quoted flow rate (for example if the quoted flow rate is 2 L/h, the average should be between 1.9 and 2.1 L/h).
- Coefficient of Uniformity:
- Compares the variation across all flow rate measurements taken from a valve unit, and expresses the result as the average closeness of measurements to the average measurement (100% indicates all measurements are exactly the same);
- The target is greater than 90% CU;
- Test lateral flow rate:
- Compares the flow rate of a complete lateral with the flow rate expected from the number of drip emitters along the length of the lateral. This will potentially identify the presence of partially or fully blocked drippers, or worn drippers which may not be selected for the specific pressure and flow rate measurements above;
- The target is less than ±5% variation from the quoted flow rate (for example if the quoted dripper flow rate is 2 L/h, dripper spacing is 0.5 m, length is 100m, the expected flow rate is thus 400 L/h, measured flow rate should be between 380 and 420 L/h).
The drip irrigation evaluation tool allows growers to compare the performance of their own drip irrigation systems against the 50 sites evaluated in the almond industry irrigation performance audit.
Drip Irrigation Evaluation Tool