Moving and pressurising water requires a lot of energy. As a result irrigation is the major energy user in growing vegetables.
For most growers, improving productivity, i.e. increasing the revenue for the amount of energy used, is more important to the bottom-line than simply improving the energy efficiency and reducing energy costs.
Managing irrigation well delivers improvements in water productivity ($/ML) through increases in yield and/or quality and hence revenue per ML of water applied. In a similar way improving energy productivity ($/KWh) will be more about increases in yield and/or quality and hence revenue per KWh of energy used. This productivity approach will be a stronger motivator than simply reducing the cost, whether it is for water or energy.
There are three areas where irrigation improvements could increase energy productivity or reduce energy usage, these being:
- Crop management.
- Irrigation system design and maintenance.
- Pump efficiency.
Similar reductions in on-farm energy use can be made by improving either pump efficiency or irrigation system design and maintenance. For example, in a survey of 16 vegetable growers in the Peel-Harvey valley, half the potential saving came from fixing up the irrigation system and the other half from optimising pump and motor performance. A wide range of irrigation tools have been developed to assist growers, consultants and designers to improve irrigation management. Many of these will also improve energy productivity and/or reduce costs.
Water use efficiency varies hugely between growers. For example, a study of citrus growers found a 10x difference in water productivity, ranging from 0.8t/ML to 8.0t/ML. Converting this to energy productivity produces a range of 0.4 to 3.5 tonnes produced per 100 KWh of electricity used for irrigation.
In general, the higher the head pressure, the more energy is required.
|Irrigation system||Total operating head
|Furrow - river||10||45|
|Pivot or linear move, low pressure||40||181|
|Drip or micro irrigation system||50||226|
|Spray - river||55||258|
|Traveller - river, medium pressure||85||385|
|– bore, medium pressure||90||407|
|– high pressure||120||543|
Irrigation scheduling is an important aspect of improving crop productivity. There are many guides to irrigation scheduling including;