Potatoes have long been regarded as the major UK irrigated crop. Particularly sensitive to water stress, they have a relatively shallow root-zone and are often grown on soils with low to medium water holding capacities. “Irrigation can have a major impact on both yield and quality,” says agronomist Tom Geraghty, project manager of the Precision Irrigation System (PIC). “Sufficient water in the early stages of the crop helps control common scab. During the bulking stage if the crop is deprived of water it can suffer major yield and quality loss. With specifications and quality controls for fresh produce becoming increasingly tight, market prices vary widely depending on the quality of the produce.”
Multiple small measures contained in the new Water Act mean that per unit, water is set to become more expensive to use and abstract. Growers are also likely to be called upon to gather comprehensive data to help demonstrate efficient use of water. While helping to justify to the Environment Agency (EA) that water is being well managed, it will also have a role to play in defending applications for abstraction licence renewals.
Growers using more efficient irrigation systems, that keep water use below 20m3 per day, will not require abstraction licences. However, in the future licences will be required for trickle systems. Growers using trickle irrigation in situations where they were previously unable to obtain a licence, remain unlikely to be granted one.
“As from July 2012, licences revoked due to environmental damage will not qualify for compensation for the licence holder,” says Geraghty. “Indeed, in future, farmers may be held liable for any damage to property or wildlife habitats caused by abstraction, with the burden of proof lying upon the abstractor. It is likely that many licences will be revoked if they lie near sensitive wildlife habitats and do not show efficient, careful water use.”
More stringent rules on the use of pesticides and fertilisers are also likely if additional powers are given to the EA to prosecute diffuse polluters. Farmers will therefore have to show good practice and collect data on water management on farm to avoid prosecution.
“New abstraction licences are likely to run for 12 years making it more difficult to secure a return on investment in irrigation capacity and equipment,” warns Geraghty. “This is already the case in East Anglia. Licences may also be timed to coincide with CAMS reports, therefore enabling renewal to be influenced by the report’s findings. By-right licences will not be time limited, but could be revoked if causing serious environmental damage.”
Proposed new four-year ‘use it or lose it’ regulations may be difficult to manage on certain rotations. As a result, there may be an increase in the number of new licences available.
In response to existing legislation, the market in the transfer of water rights is being encouraged and will be regulated by the EA using similar criteria and procedures used for new licence applications.
“In the short term, it is likely that the test of reasonable need will still apply to demonstrate why the resource is required,” says Geraghty. “Detailed record keeping, business benchmarking and best practice will all help to establish a case.
“In the longer term, it is likely this may be dropped in favour of market forces. A trade that can demonstrate environmental benefits will be looked upon favourably. Once again good management must be demonstrated, so the importance of measurements and record keeping cannot be over emphasised.”
Three techniques exist to estimate a crop’s demand for water. These are: experience, modelling and measurement.
“Experience must be supported by measurements and record keeping,” says Ben Sartain of Fairfield Control Systems - the Nottinghamshire based company at the leading edge of controlled automation. “Best practice is demonstrated by the use of sensors to monitor water storage, water usage, soil and environmental conditions. These can be used to produce a detailed record of the crop’s irrigation requirements.”
With access to accurate data regarding the previous day’s water usage and environmental conditions, irrigation schedules can be calculated based on the crop’s demand for water using actual movements in soil moisture deficit.
Traditionally, Penman-Monteith evapotranspiration models have been used to predict water usage and a water balance sheet used to decide when irrigation is required, says Sartain. “The demands on management time are significant and support is often required from an irrigation consultant. The model is only as good as the data entered. The irrigation schedule produced is usually updated weekly and is not responsive to local storms or rainfall patterns.”
Billed as the complete irrigation management tool, the Precision Irrigation Control (PIC) system continuously monitors conditions in the field, aiding irrigation decision-making and efficient water application. Developed by Fairfield Control System, this highly flexible automatic demand led system takes readings from different sensors, stores them in a data logger and remotely transmits the data to a computer.
The PIC software accurately identifies areas of moisture deficiency and, linked to a 10-day weather forecast, provides growers and irrigation consultants with all the information needed for improved decision-making, as well as detailed record keeping.
Users have access to detailed real time data on which to make informed irrigation decisions. Developed in consultation with growers, the unique PIC software accurately indicates areas of moisture deficiency. Last recorded readings for all sensors give the user a snapshot view of conditions. For more detailed information, and to view historic data and trends, PIC allows the user to plot the data on a graph.
“Using PIC, you do not have to go to the field to gather data - you can access the information from your computer at home or in the office,” says Geraghty. “While it is obviously still important to visually inspect the crop on a regular basis, the system saves time and improves the accuracy of water usage helping to ensure yields and quality are maximised, as well as water efficiency. Highly flexible, all systems are tailored to suit individual needs and requirements.”
At Castle Farm at Stibbington near Peterborough, 120 acres of salad potatoes are being grown on sandy loam. Untill now irrigation decisions on the farm have been based on readings taken twice daily from tensiometers in the soil.
“With fields spread out over a five mile radius, it has proved time consuming and not particularly accurate,” says Mike Bradshaw. “Quality is king with salad potatoes - good scab control early in the season is vital - adequate irrigation plays an important role in control.”
PIC was installed on Castle Farm earlier this year. “Using the real time data downloaded daily, we have irrigated more and earlier,” says Bradshaw. “It has helped us improve our irrigation efficiency - I can see where water is being lost and predict when we need to water rather than irrigating whether it is needed or not.
“We started harvesting in mid-June and the quality has been excellent. PIC is a useful management tool - through improving irrigation decision making it has helped us achieve superior quality potatoes while saving time.”
“Farmers are operating under increasing cost pressures,” says Geraghty. “Accurate demand based irrigation while helping maximise yields of high quality produce, can deliver cost savings in water, energy, labour and fertiliser.”
Using the latest IT technology, it is now possible to maximise efficient water usage, while generating the necessary data to demonstrate why the water is required and that it is being managed to its best potential. PIC has been developed to help bottom line profitability by helping to reduce the labour element and making the best use of water resources.”
IRRIGATION BENCHMARKING - THE FUTURE
The word efficiency is frequently used when discussing irrigation - but what does it mean? Does it relate to the quality of the crop, or the yield? Or perhaps how much water was used, the final profit of the holding or the environmental impact?
According to Geraghty, efficiency refers to all of these and more. “Efficiency is not just about getting the most out of the irrigation assets, it is about managing them with due care for the environment, good crop management and profit, as well as with the long term effects of any actions in mind,” he says. “Irrigation benchmarking must therefore take a large number of parameters into account, and find an effective and comparable value for each performance indicator.”
Here again, challenges are encountered - while it is easy to assign a monetary value to labour or crop yield, how can monetary values be put to an environmental impact, or indeed water itself? The cost of water varies greatly according to its source and its use. Mains water is highly expensive compared to water collected in winter from a watercourse. What is more the value of water to wash down a yard is probably less than if used to irrigate a field of potatoes in July.
“To be meaningful, irrigation benchmarking must be conducted using many indicative parameters, and used to compare grower with grower, area with area, even soil type with soil type,” says Geraghty.
BENCHMARKING IN PRACTICE
The International Water Management Institute (IWMI), together with the World Bank and other organisations, has set up an international benchmarking scheme that runs on this principle, putting system monitoring in the hands of practising irrigation managers. Using factors such as cost recovery, gross production, output per unit water consumed and drainage, irrigation managers can plot their operations against other growers in similar situations.
“Using this benchmarking system it is possible for a user to find that while an irrigation operation scores exceptionally highly in terms of profit per unit water, it can score poorly when it comes to environmental impact, or depreciation of hardware,” says Geraghty. “Alternatively, the exercise may conclude that while an operation is very cost-effective in regard to equipment and labour, it is not getting the most from the irrigation system.
“In short, benchmarking is essential in a market increasingly driven by demands for efficiency, traceability, and reduction in environmental impact. To be effective, it needs to be consistent and free from significant error, while using parameters that can be easily measured by growers themselves. The guidelines for measurement need to be clear and concise, and applicable to every form of abstraction, irrigation, cropping, and market form.”
While irrigation benchmarking is an involved process, with its ability to generating comprehensive data on water use, abstraction and crop data, the PIC system can help generate benchmarking key performance indications relating to service delivery performance and productive efficiency.
“A tool for comparing irrigation costs and improving efficiency in its widest sense, irrigation benchmarking will soon become invaluable to those that adopt it,” Geraghty concludes.
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