Tips for vineyard workers
System effectiveness is one of the biggest advantages of drip irrigation. The design of drip irrigation is aimed at minimising water loss as a result of evaporation and/or runoff. In terms of system effectiveness (the efficiency with which water is delivered to the irrigation system from the irrigation dam or tap point on the farm’s border, to the point where it lands on the soil) drip irrigation performs the best with 90%, followed by micro sprinklers with 80% system effectiveness.
Correct maintenance of the system is very important to ensure that the effectiveness remains consistently high, so that all grapevines/trees receive sufficient water for maximum yields and quality. The great advantage of drip system effectiveness is therefore lost if maintenance is not correct. Basic maintenance actions for drip systems may include rinsing of lines, monitoring of effectiveness, basic maintenance and chemical treatment.
Rinsing of drip and main lines
Rinsing of drip lines (Photos 1A – 1D) is considered the basis of maintenance and should be undertaken regularly. Flow speed is very important and should be at least 0.5 m/second for effective rinsing of drip lines. An easy way to determine flow speed is to see how long it takes to fill a 1 litre container. Twelve seconds or less are sufficient for 16 mm and 17 mm lines and eight seconds or less suffice for 20 mm lines.
Rinse taps on main and sublines (Photos 2A and 2B) are a prerequisite for a good irrigation system. These enable the producer/worker to rinse these pipes only, especially if a pipe has burst, to ensure that sand does not get into the drip lines.
It is important to monitor the pressure regularly at the end of the furthest drip line. A basic pressure gauge (Photo 3) may be used. The pressure should correspond to that of the design specification of the system.
The flow rate of the drip emitters can also be tested by using a measuring cylinder (Photo 4). Measure the water that drips into the cylinder over a period of 30 seconds for example and convert this to litres/hour.
Drip system, photo 4.
It is very important to walk through irrigation blocks during irrigation to look for burst pipes and leaks so that these may be addressed immediately. Basic system components to be kept amongst supplies include different types of joints (Photo 5), as well as extra drip lines. It is important that the drip to be used in the joint should distribute the correct amount, for example 2.3 litres/hour or 4 litres/hour. Do not hit blocked drips or squeeze them with a pair of pliers. This may damage the pipe as well as the drip.
Chemical treatment of drips takes place if there is a blockage problem that cannot be sorted out by means of normal maintenance. Always try to apply the application directly to the drip lines and not to the main lines. The dirt coating that is dislodged from the main lines will be rinsed through to the drip lines and the blockage will become even worse. Products that are used mostly for this purpose are hydrogen peroxide (H2O2 – Photo 6A) and hydrochloric acid (HCl – Photo 6B). The nature of the problem will determine the product (or combination), as well as the amount, to be used. Contact your irrigation expert for a correct recommendation in this regard.
Gert Engelbrecht (Photos 1A – 1D and 4); Willem Botha, Netafim (Photos 2A, 2B, 3, 6A and 6B) and Jaco van der Westhuizen, Vredendal Irrigation (Photo 5).
VinPro viticultural consultant,