Irrigation shifts

An irrigation shift occurs when an individual block is irrigated, not when all blocks are irrigating at the same time.

There is one mainline that supplies the whole system, and a valve turns each block on/off separately, which in turn enables the operation of irrigation shifts.

We make irrigation shifts primarily because it reduces the cost of the system considerably. You need smaller mainlines, pump and filtration as the overall water flow at any one time is lower.

See the examples below.

By increasing the number of shifts, you require smaller main control head (e.g. filters, valves, etc) and lower diameter mainlines.


But how many shifts can you have and still meet the water requirement?

Calculating irrigation shifts

Step 1

Calculate the application rate of the drip line/tape you have selected in mm.

Calculate how many hours of irrigation are required to meet peak crop water requirement based on the application rate.

This output is simply the number of hours the system needs to operate to achieve the peak water requirement. However, not always do you have 24-hour supply, or you may want to utilize off peak electricity tariffs.

Calculate how many shifts you can operate, based on how many hours you have/want to use the system.

The above is all calculated on the assumption of unlimited water source in terms of m3/hr (gpm) – both the water source and the pump.

It is recommended not to irrigate more than 20–22 hours daily, and to leave spare time for maintenance and malfunctions.

Calculating the flow required m3/hr to determine if the flow requirement can be met.

First convert the application rate (mm/hr) to (m/hr). Working in m will make it easier for the next calculation.

As there are 10,000 m2 in a hectare, multiply the above figure by 10,000 to obtain the flow per hectare.

Multiply the above figure by the amount of hectares in each block.

Calculating the flow required in gpm to determine if the flow requirement can be met.

The USA system uses inches of applied water per hour (in/hr), which can be converted to gallons per minute per acre (gpm/ac) by multiplying by a factor of 452.54. For example:

A 40-acre set would require a flow rate of:

The factor of 452.54 was derived using the following formula:

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