As with all machinery, pumping systems will decline in efficiency over time, either due to abnormal operating conditions, or through normal wear and tear. To keep the system functioning at peak efficiency it’s important to monitor pumping performance on a regular basis, but it can be difficult to pick up gradual declines in performance by observation only. Unless regular checks on the system are made, it’s likely the decline in efficiency won’t be noticed, until the system fails to the point where there are significant equipment and or crop losses.
As the cost of energy, and the pressure to reduce greenhouse gas emissions increases and combines with the problems energy supply companies have maintaining supply during peak times, the issue of energy efficiency becomes much more important. Field tests have shown there is a large variation in pump efficiencies and costs in many of the irrigation sectors in Queensland, and the nursery industry is no different. On-farm pump performance tests completed over a period of 10 years, as part of the Rural Water Use Efficiency Initiative, found that irrigation systems that functioned poorly were often linked to poor pump performance. This testing showed a significant variation in efficiency, with some results as low as 23% and an average around 48%.
Hand watering is a common practice in many production and retail nurseries, with 55% of production nurseries using this method to some degree. Sometimes hand watering is regarded as an efficient irrigation method without full knowledge of the underlying principals and actual efficiencies of alternative methods. During 2008, DPI&F, Qld conducted an investigation into the efficiency of nursery irrigation practices on behalf of NGIA. This investigation surveyed a number of production and retail nurseries to examine labour costs and water use associated with hand watering, and compared it to the calculated costs of other irrigation techniques.
There are many ways that water can be saved in the nursery. Here are 10 tips.
Measure water use
The first step in saving water is to measure how much you are using. This allows informed management and costing decisions to be made based on facts, not assumptions, and allows cost savings to be quantified. The easiest way measure your water use is by using a water meter, but, if a water meter isn’t available, water use for each growing area can be calculated from the measured flow rate of the sprinklers. Rainfall and evaporation should also be recorded, as these have a major influence on water use, and this information is useful when comparing water use from year to year.
NIASA, the Nursery Industry Accreditation Scheme Australia advocates a ‘free chlorine’ residual reading of 2ppm or 2mg/litre following at contact period of 20 minutes for the successful treatment of irrigation water. There are a range of test kits, test strips, and meters available for accurately measuring the chlorine concentration in the disinfested irrigation water and also capable of testing for pH values.
Pump cavitation is a common pumping problem which, if not addressed, leads to impeller surfaces and pump bowls pitting and wearing, and eventually leads to mechanical destruction of the pump.
The term evapotranspiration is simply the sum of evaporation and transpiration. It is the water lost to the atmosphere from the ground surface by evaporation and from the plant by transpiration.
Drip irrigation is a method of irrigation that can be used in nurseries to save water and money. It is an effective and efficient system that simply drips or sprays the irrigation water directly onto the growing media surface where it is slowly absorbed. A well designed drip irrigation system improves irrigation uniformity and loses virtually no water to runoff, non growth areas, wind or evaporation. Irrigation scheduling with drip systems can be managed precisely to meet nursery crop demands potentially providing increased growth and quality. Drip irrigation systems generally do not require high system pressure and have relatively low flow rates allowing for efficient, cost effective pumping. Drip irrigation systems can be adapted to irregular shaped growing areas and are ideally suited to those larger container plants used as wind breaks around the boundary of growing areas.
Chlorine is extensively used by growers in Australia to disinfest their irrigation water, but not always successfully. Chlorination of irrigation water with high levels of dissolved iron and/or manganese is not recommended as chlorine oxidises these elements to form precipitates that can potentially clog up an irrigation system. Oxidising iron is a relatively quick process and can be managed by filtering the iron precipitate out of the system, however oxidising manganese is much slower and can potentially precipitate out later in the irrigation system, clogging valves, solenoids and sprinklers.
How much can an efficient sprinkler layout set up to Best Management Practice save? The owners of Bunneys Lane Nursery had decided to increase their growing area, and this presented an opportunity to install a more efficient sprinkler layout and identify areas where cost savings could be made.
Production nurseries in the South East corner have welcomed the rainfall received in recent weeks. The fairly widespread rainfall has swelled most onsite nursery storage facilities, many to very near their capacity, giving some water security to each nursery operation and providing business confidence for the immediate future.
The irrigation sprinkler field day held at Redlands Research Station in early September attracted forty-five participants along with a substantial amount of rain. The much needed rain did cause some alteration to the original program and forced relocation indoors to the research station’s conference facilities. The afternoon began with the welcome bbq on the adjacent terrace which provided participants with the opportunity to network and ask all those burning questions.
Sodium hypochlorite (Chlorine) is frequently used within the nursery industry in Australia for the disinfestation of water used for the irrigation of nursery stock.
Sodium hypochlorite over its long history of use has proved suitable for most applications within the nursery industry and is considered effective, simple to dose, easy to monitor and relatively safe to handle and store. It is a recognised as a suitable water disinfectant under the NIASA, Nursery Industry Accreditation Scheme, Australia when used according to the guidelines. Chlorine does have significant limitations in the spectrum of disease organisms that it is effective (efficacy) against and is generally considered the minimum standard for water disinfestation.
Many of the nurseries that I work with are taking our advice and implementing changes in their business at very little cost. It is a tough time for many production nursery owners at present, so expenditure on larger capital projects is inclined to be in the future plan rather than a current projects file. However, some operators have found that spending a little can reap great rewards.
It is becoming more and more evident as the present drought continues that the community expects the efficient management and use of any water resource. The single use of water for irrigation and later release to waste is no longer acceptable to the regulators or the community. Nurseries operating under the newly established environmental management system, EcoHort™, are encouraged to include water reuse or recycling in their future planning activities.
Upgrading to a variable frequency drive or VFD pump set can provide a number of benefits to nursery owners and also affords a significant level of flexibility to the grower. The expected benefits for nurseries in upgrading to a VFD pump set are a reduction in pumping costs and the ability to operate irrigation zones with different sprinkler numbers and flow requirements. The soft start of VFD pump sets has also provided a reduction in main line blow outs in many nurseries, especially those older operations. Installing a larger pump is sometimes hindered by the electricity service available to the pump shed and upgrading to a VFD pump set may allow a larger capacity pump to be installed.