1 Executive Summary
The purpose of this project was to test, under field conditions, a set of indicators developed for sustainable irrigated agriculture. This has been part of an ongoing programme of research into indicators of sustainable agriculture.
The set of indicators developed for MAF by Lincoln Environmental in 1996/97 was used as the basis of the trial. These indicators are given in Table 1.1 along with comments about each indicator, arising from the trial.
The trial included six farms in the Central Canterbury area, four dairy farms and two arable farms. The farms were loosely paired. Two dairy farms had border strip irrigation systems - one with narrow borders and a big gun and the other with new wide borders. Two dairy farms had spray irrigation - one with travelling irrigators and the other had a new centre pivot system. One of the arable farms had siderolls and hand shift sprinklers and the other a combination of travelling irrigators and a sideroll. Three of the farms were also involved in a companion field trial conducted by Lincoln Environmental to evaluate a set of Best Management Guidelines for irrigation practice.
Data was collected from each farm to determine as many of the indicators as possible and the results were discussed with the farmers involved. All indicators were determined historically at the end of the 1997/98 season. Due to difficulties encountered on all properties with installing water meters no daily water flow data was available for the whole irrigation season for any of the properties.
Indicator testing on the dairy farms concentrated on production and soil indicators. On the arable farms indicator evaluation was targeted at financial and production indicators for individual paddocks rather than the whole farm.
On two of the spray irrigated farms detailed irrigation system audits were carried out. These highlighted technical problems with system design and operation that helped explain some of the indicator values obtained.
The study showed that it was relatively easy to evaluate and interpret the economic/technical indicators but that the environmental indicators were more elusive, both to determine and to interpret. The farmers were interested in the results, particularly the economic/technical indicators. They could see how these could aid in future decision-making processes, both capital investment and day-to-day management. There was a consensus from the farmers that it would be valuable to continue monitoring in subsequent years.
Table 1.1 Recommended Indicators of Sustainable Irrigated Agriculture and Comments Derived from this Project
Economic |
|
1. Annual net operating profit after tax ($) |
Insufficient information available to evaluate this for all dairy farms. For arable farms evaluated gross margin for each crop. |
2. Quantity of crop or product produced per unit of water used for each crop (t/m3) |
Easy to determine once total volume of water used had been estimated. Farmers perceived as being useful. |
3. Profit per unit of water used ($/m3) |
Not determined for dairy farms. Useful for comparing value of water for arable crops. |
4. Quantity produced per hectare for each crop or product (t/ha) |
Already used by farmers as standard of comparison. |
5. Quality of produce (% of each crop or product at each grading level) |
Difficult to obtain meaningful data. Not evaluated. |
6. Annual energy used to operate irrigation systems (kWh) |
Required some effort to obtain this information. |
7. Energy used per volume of water pumped (kWh/m3) |
Easy to determine once total volume of water used had been estimated. Farmers perceived as being useful. |
8. Labour units per irrigated area (hours/hectare) |
Easy to determine once total volume of water used had been estimated. Farmers perceived as being useful. |
Environmental |
|
1. Resource consents obtained and complied with |
All farmers stated this to be so. Not included in further discussion. |
Evaluated from soil water holding capacity, total organic Nitrogen and carbon, pH and conditions of soil surface aggregates. |
Easy to obtain but expensive. Not obvious how these relates to irrigation system or management practice. |
3. Daily volumes of water flowing onto farm for each crop (m3) |
Not obtained due to difficulties with water meters. |
4. Daily percentage of water flowing onto the farm that is stored in the root zone (derived from soil moisture measurements in and below the root zone) |
Not obtained due to difficulties with water meters. Also requires continuous soil moisture monitoring. Expensive to obtain. Alternative seasonal indicators proposed and tested but proved to be of limited benefit. |
5. Daily visual assessment of the amount of ponding or surface water runoff |
Not obtained. Would require farmer to record every day. |
6. Maximum water abstraction rate each season (m3/day) |
Estimated from resource consents or bore performance. Interpretation of meaning not obvious. |
7. Lysimeter based measurement of nitrogen leaching below the root zone (effluent irrigation only) |
Not obtained. Expensive. |
8. Agri-chemicals and fertiliser used per quantity of crop produced (kg/ha or l /ha) |
Easy to determine but meaning doubtful. Does not take into account timing and amount of each application. |
Social |
|
1. Record of any abatement notices |
None recorded. |
In summary the conclusions of the study are:
- Accurate water measurement proved to be the greatest limitation for determining the indicators. This could be addressed through the development and use of a low cost portable flow meter on spray irrigation systems. A suitable solution for surface irrigation systems is still a problem.
- The accuracy of total water application amounts based on area by depth calculations should be improved by measuring application depths under spray irrigation with 'catch-cans'. Once again a suitable alternative for surface irrigation is a problem.
- Most of the indicators were easily determined. The others were essentially impossible without expensive continuous monitoring.
- Interpretation of the economic and technical indicators was relatively straightforward and meaningful to the farmers as they related to short-term economic goals.
- Interpreting the meaning of those environmental indicators that could be determined was more difficult. These tend to relate to farmers' long-term goals and are more 'fuzzy'.
- The system audits proved to be useful in identifying technical system problems that related directly to some indicator values.
- These indicators will be useful to irrigators within a 'Plan-Do-Check-Act' cycle of improvement toward sustainable management.
In summary the recommendations of the study are:
There is a genuine need for a low cost flow-metering device to be developed.
Finally, a point that we believe cannot be made too strongly:
These indicators are not sufficient or accurate enough to 'point-the-finger' at individual irrigators by way of inter-farm or inter-system comparisons. We feel strongly that such a use of indicators would be contrary to the 'true spirit' of sustainable management. Rather these indicators should be used as tools to aid in the development and evaluation of sustainable management practices.
Contact for Enquiries
MAF Information Services
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PO Box 2526
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