Topics covered in this article include:
Capacity to match crop water requirements
The primary decision is whether a drip or microjet irrigation system has the capacity to supply sufficient water to match crop water requirement.
Ease of scheduling irrigation
In most cases, microjet irrigation wets a larger volume of soil than a drip system.
Relative installation and operating costs
Unfortunately the cost of installing and operating a pressurised irrigation system increases with flow rate.
Susceptibility to blockages
In the early days of micro-irrigation it was usually assumed that drippers blocked more easily than microjets because of their smaller orifices.
Likelihood of damage to emitters or laterals
Microjets mounted on stakes are generally vulnerable to damage in orchards, particularly during harvest and pruning.
Grass and weed growth
Microjets wet a larger soil surface area than a drip system. This encourages the growth of grasses and other weeds (Figure. 1).
Effects on soil structure
Maintaining soil structure in the root-zone on heavier soil types is more difficult with drip irrigation.
Ease of applying fertilisers for nutrient supply
Fertigation is a common practice in both microjet and drip systems.
Susceptibility to waterlogging
Microjet irrigation is less susceptible to waterlogging in the root-zone because of the relatively long interval between irrigation.
Irrigating with saline water
When irrigation water is saline, it is generally considered that drip irrigation is the best system to avoid the build up of salt in the root-zone.
Some protection from frost can be achieved with microjet systems (Figure. 2).
Drip irrigation is recognised as the most efficient system to deliver water directly to the crop root-zone with minimal understorey evapotranspiration (soil evaporation and weed and cover crop transpiration).
Ability to manipulate growth and fruiting
A smaller active root-zone under drip irrigation helps to reduce tree vigour, contain tree size and promote fruitfulness.
- It can be easier to manage a microjet than a drip system, and management is not only associated with technical ability but also with time available.
- Irrigation headwork breakdowns and pipe breakages in drip systems that operate daily increases the risk of crop losses.
Overall, given proper installation and management, there is little difference between microjet and drip systems unless particular circumstances dictate the choice of one system over the other.