Learn Commercial Irrigation Online
With water resources under increasing pressure in many parts of the world; it is critical that we manage the water we have in the very best way. Water is critical to all human and other life. It should neither be wasted, nor contaminated; and this course can help you toward both of those goals
- This course focuses on broader scale water management than our other course: Irrigation (gardens)
- Students are guided by horticulturists and scientists with practical experience as well as formal training on the subject.
- You can commence any time; study at your own pace and work from anywhere in the world.
This course complements Irrigation (Gardens), but can also be studied as a stand alone course. Most students however would normally choose to study Irrigation -Gardens, first..
“This course is valuable for anyone in charge of an irrigation system or working in the irrigation industry servicing enterprises such as nurseries or turf facilities. It will show the best ways to run systems efficiently.” - Tracey Morris Dip.Hort., Cert.Hort., Cert III Organic Farming, ACS Tutor.
Course Structure and Content
There are 8 lessons in this course:
- Waste water and recycling
- Teaches how to minimize water wastage in irrigation.
- Measuring water usage
- Examines how to schedule irrigation for a large scale situation such as a large nursery, crop, turf, garden or pasture.
- Presents an analysis the design of different drainage systems
- Irrigation controllers
- Looks at the formulation of procedures to operate irrigation controllers, for appropriate tasks
- System maintenance
- Examines the maintenance of irrigation systems, both small and large scale
- Examines the management of fertigation of plants through an irrigation system
- Design evaluation
- Looks at the evaluation of the design of large scale irrigation systems
- System design
- You will learn how to design an irrigation system, including its drainage
Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.
MINIMISING PLANT REQUIREMENTS
The watering requirements of your plants can be minimised in the following ways:
- By choosing plant species and varieties that best suit the local climate.
- By maintaining a well balanced fertile soil (appropriate to the plants selected).
- By watering (only if absolutely necessary e.g. when first establishing plants) in the cool of the day
- By using micro irrigation systems e.g. trickle systems where possible. These are much more efficient in their use of water.
- By slow, thorough watering. A thorough deep watering once or twice a week will be more effective than a light watering every day or two.
- By avoiding spraying water on windy days.
- By reducing excess evaporation. This can be achieved by keeping bare soil covered. Mulches, as well as reducing weed growth will reduce evaporation. Compact ground covers will slow evaporation from the soil but they will use a lot of water themselves. Larger plants will shade the soil and limit evaporation but they can make getting water to the soil in the first place rather tricky.
This is a concept of water conservation through creative design and use of appropriate plants and landscaping materials. The principles can sometimes be applied to irrigation systems. In many developed nations landscape designs have tended towards European style agriculture/horticulture. This may be suitable for those areas where conditions (e.g. climate) suit those type of plants, however in areas where conditions are much warmer and drier, the European styles can be difficult to maintain and are generally very wasteful of water. Xeriscape systems (‘xeros’ is Greek for dry) feature:
- Limited area size
- Low volume irrigation
- Moisture sensor controlled watering systems
- Diversion of rain water run-off to garden areas
- Drought tolerant plants.
Water wastage during irrigation has always been a problem for irrigators in the past. Given that water is such a valuable commodity, water management has received a good deal of research in order to rectify the situation. Wastage occurs in numerous ways. These include evaporation, seepage and runoff. The key requirements of water use management are efficiency and even distribution. That is, the available water should be utilised by the plants in order to aid quick, healthy even growth. Problems such as water-logging or salinity should be monitored, and, in many cases, can be avoided with good irrigation management techniques.
TYPES OF WATER WASTAGE
A certain amount water loss through evaporation is inevitable. Water that is stored in ponds and lakes are more susceptible to evaporation due to large open surface areas. Flood irrigation too, will have more severe evaporation than trickle or drip irrigation. In all cases irrigation that is undertaken at night will suffer less from evaporation losses. Evaporation also takes place through the plants that are being irrigated. This is referred to as transpiration and as a natural process of plants cannot strictly be viewed as water wastage, however it is an important factor in estimating crop irrigation requirements.
- Transpiration: the loss of water as vapour generally through the stomata of leaves
- Evaporation: the loss of water as vapour from a free water surface
- Evapotranspiration: is the combination of the above two factors which
is essential when estimating irrigation levels for crops.
The loss of water through evaporation can be controlled either by the type of irrigation employed or by the timing of irrigation practises in relation to local climatic conditions.
Seepage is another factor which contributes to water loss. It too, is impossible to check completely. Seepage occurs through the base and walls of canals and dams which are usually constructed from local available soils. The compaction and permeability of these soils are what accounts for the levels of seepage.
Run-off is a result of too much water, this may be as a result of irrigation or due to excessive rainfall, it may be further intensified by poor drainage. It is the most controllable factor of water wastage but all too often is not given the consideration it deserves. Many variables determine the optimum irrigation rate. These include soil type and quality, climate, soil suction levels (which can be tested using a tensiometer), particular crop requirements, recent watering/rainfall history of the area to be irrigated. Run-off can be reused if the appropriate drainage and recycling techniques have been included into the irrigation design, thus wastage can be minimised.
Over-spray occurs when irrigation devices – such as sprinklers – deliver water beyond the desired irrigation area. Over-spray results in excessive water use, and thus wastage. Over-spray can affect crop growth where irrigation is timed to deliver a particular quantity of water, since not all water that is delivered can be utilised by the crop. Selection of appropriate irrigation methods and emitters, and correct calibration of irrigation equipment, reduces or eliminates the problem of over-spray.
Often in irrigation the water to be used is scheduled. For instance, the farmer may have talked to the water bailiff and ordered so many megalitres to be available for a certain day of the week. The water bailiff then releases that amount of water into the river or canal system. There are times however, when the water is not required due to a heavy local rainfall or evaporation rates are markedly less than expected. In this instance, the water that is earmarked for the irrigation is not going to aid the crop but more than likely hinder its growth. It will still have to be paid for and will be wasted.
The bailiff may be able to allocate the water elsewhere but the main strategy to avoid this scenario is to avoid scheduling until you, as the irrigator, are certain of when and how much water you require. This is very much a good management issue and can be especially critical in times of uncertain water allocation due to drought.
RECYCLING WASTE WATER
Waste water that has been used for domestic or commercial purposes can be treated and recycled thereby making it suitable for irrigation. The water is treated in a number of ways including removal of solids, biological treatment and disinfection. However, misconceptions still exist over the actual quality and health aspects of treated water, and as a consequence much of this treated water which is high in nutrients is flushed into our waterways where it contributes to environmental problems such as blue-green algae. This same high nutrient content water is actually a positive aspect from an irrigator’s viewpoint as it contains nitrogen and phosphorus.
Water recycling can be practised on a more localised scale also. Water that has already been used for irrigation or other purposes (hosing down cattle yards) will have deteriorated in quality due to the absorption of solids such as fertiliser, organic matter, etc.. Often, it is best to allow this water to settle in a dam since this will allow solids to sink to the bottom at which time the water will again be of a higher quality and can be reused.
The most common approach to recycling excess water is to design channels and canals in such a manner that drainage channels flow into primary channels or dams that service other areas to be irrigated. This system, to be most effective, needs to have good design of its levels and gradients.
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