From Commercial Growers
With climate change impacting on the agronomic, economic and environmental aspects of horticultural production, growers are dealing with changing water availability and increasing energy prices. Therefore, they must look to invest in the best possible irrigation system- to benefit both themselves financially and the environment, without sacrificing the quality of their crop.
Trickle / Drip
Described as irrigation of the future, this method is accurate, energy efficient, easily automated and produces high yielding quality produce, whilst providing water savings and environmental benefits that the government seek. Trickle/Drip irrigation is well established in soft fruit, orchard fruit, salads and glasshouse sectors.
How it works – Trickle irrigation consists of a system of small diameter plastic pipes with specially designed emitters that enable growers to apply small quantities of water (2-10litres/hr) to crops at frequent intervals (1-3 days). Using this system only part of the soil profile around the plan roots becomes wet meaning frequent irrigation is needed to make sure the plants are well supplied with water. Due to the direct connection between the irrigation system and plant, as well as the fact that the fertiliser can be added to water, the grower is able to achieved water savings, improved yields and crop quality. Additionally, the low operating pressures (typically 1-2 bar) mean lower energy costs and automations thus lower labour costs. This method requires a more specific approach to irrigation management, the grower must rely on instruments for information such as, flow meters, timers and pressure gauges to monitor water application and soil moisture probes to monitor water movement and wetting.
Trickle irrigation is adaptable to a wide range of agro climates, soils and crops. It is ideal for perennial orchards and soft fruits but is increasingly being used for seasonal crops, including field-scale vegetables and salad crops.
This method is a mobile system that can apply water precisely, particularly when spraying directly onto the crop canopy. When using this system, energy requirements are low because pumping pressures are only 3-4 bar, less than half the pressure of a rain gun. A typical modern boom compromises a set of fixed spray nozzles located on a gantry mounted on a 4 wheel chassis which is connected to a hose-reel. Recent improvements in design including reduced energy needs, uniform application and fine sprays that minimise soil splash onto delicate crops. These developments have made booms more popular among field-scaled vegetables and salad growers.
Booms can be single-handedly set up and manoeuvred and can irrigate 35-72m wide strips and are well suited to large and flat rectangular fields. Application rates are high and so care is needed to avoid runoff on low infiltration rate soils.
Solid set systems using rotary sprinklers are becoming increasingly popular, and are now being used on seasonal field vegetables and salad crops as an alternative to rain guns. Like booms, sprinklers operate at pressures of 2-3 bar. More sophisticated electronic systems, such as those used for sports turf irrigation using remote controlled switching of solenoid valves enable these systems to apply water more frequently- with a greater degree of flexibility and precision.
Improved irrigation scheduling – when to irrigate and how much to apply – using sophisticated equipment to measure and monitor soil moisture is now becoming standard industry best practice. Precise scheduling requires precise water application. Both mobile and solid set sprinklers are now able to meet these requirements.
An Ebb and Flood system is a versatile system that can be used within a variety of growing conditions. It works using a submerged pump, that is connected to a timer. When the timer activates the pump, the nutrient solution is carried into the grow tray and when the timer deactivates the pump, the nutrient solution flows back into the reservoir. The timer is usually set to come on several times a day, however this is dependent on the type and size of plants, the temperature and humidity of the growing environment.
Ebb and Flood is a water efficient, high-tech system, but demands the careful control of soil borne diseases, as well as close attention to soluble salt levels in the solution. This system may also prove problematic if there should be a power-cut or pump and timer failure, as if watering cycles are interrupted the roots can dry out quickly. However, with close attention and efficient management this system will prove very effective in water savings.
Modern systems such as booms, close-spaced solid set sprinklers and drip irrigation can improve water application efficiency, but they do depend on how well-managed they are. Good scheduling requires an in-depth understanding of your crop water needs and an accurate knowledge of soil water status on a day-to-day basis. Growers can use technical scheduling methods such as simple tensiometers and electronic probes that monitor water contents at different depths and can show water movement in soil profiles. Achieving higher levels of uniformity and measuring what happens in the field, will enable you to schedule water applications more accurately, which will lead to water saving, reduced costs and better quality crops.