Getting the most from your irrigation system

Although often not the most expensive part of an undercover growing system, the irrigation infrastructure can be likened to the cardiovascular system of the human body – the essential system responsible for conveying water and nutrients to our highvalue, sensitive crops being grown in the climatic environment created in tunnels or greenhouses.

The role of the irrigation designer entails not only planning the system in terms of water and energy requirements based on sound principles as one would for any new irrigation system, but due to the nature of undercover irrigation systems also giving particular attention to the quality of the water supply, carefully selecting the most appropriate micro-irrigation system for the growing system, and making provision for the water required for climate control and other peripheral systems. Undercover crops are often sensitive to pH, and nutrient dosing require EC monitoring and control. The water supply may therefore require pH correction through acid injection, and the correct nutrient dosing system must be specified to be able to maintain the required injection rates. The effectiveness of the automatic dosing machines must also be checked in the field with an appropriate monitoring system using handheld EC meters. Physical water quality also has to be addressed by means of effective automatic filters to remove any physical impurities from the water before it enters the system, to prevent clogging of emitters. As far as the irrigation system is concerned, water is most often pointapplied to the growing medium or soil with drip irrigation. Inline drip irrigation is mostly used in soil, while button drip with tubes and stakes are used in growing bags and pots. In the case of nurseries where high concentrations of small plants need to be irrigated, overhead irrigation by means of micro-sprinklers is used. In all applications, the use of high-quality products from reputable manufacturers is of great importance to ensure uniform water applications. Where crops are grown in soil bags or pots, or in the case of hydroponic systems, consideration must also be given to the drainage and/or recirculation system. This will entail careful planning of the whole system to ensure that it is laid out at suitable angles for water to drain correctly, and designing the necessary systems to remove or recirculate the drainage water. The irrigation designer may also be required to make provision for additional

As far as the irrigation system is concerned, water is most often point-applied to the growing medium or soil with drip irrigation.

8 FRESH PRODUCE

However, these outlets need to have a market agent or more to ensure a steady flow of the main consumer lines such as potatoes, cabbages, beans, onions and more. This effects an on-going flow to the market by retailers and spaza shop keepers,” according to Francois.

CHANGING THE ACT

APAC is currently busy changing their Act (Act 12, 1992) and they have now prepared a new Act with Department changes. This was discussed with Minister for Agriculture, Mrs Thoko Didiza and presented to the Agricultural Committee to be passed by Parliament. Francois Knowles in his capacity as Registrar at APAC presented to the Committee in person. The Department of Agriculture’s main reason for changing the Act is to enable us to increase our service level to the producer and also to protect him in his dealing with fresh produce agents. At the same time, this will benefit the markets too. Currently the market agencies perform well and within regulations, but export and livestock agencies also need to be regulated far better. In essence, if an export agent or livestock agent steps over the line in terms of ethics or undesirable business related acts, APAC should be able to execute disciplinary hearings which may lead to the offender losing his business license. There is also the need to create Trust accounts at livestock and export agencies. They will have to fund towards the Fidelity Fund (the same as fresh produce agencies currently do) which enables to assist a producer which lost money through an agency default (in case of theft and fraud). “Communications between APAC and agencies, markets, producers and local and National Government is sharpened up to fulfil in the needs of feeding millions of hungry mouths and rebuilding trust in a South African food chain; exports and all that runs efficient,” Francois concluded. JS

water distribution infrastructure such as overhead cooling systems using misting sprinklers or wet walls for evaporative cooling. Furthermore, a system for supplying clean water to different parts of the farm may be required for filling of fertiliser tanks or hand water in the grow houses. The relationship between the grower and the irrigation designer is of great importance to ensure the most appropriate system is planned from the start and management problems are addressed timeously for the grower to get the optimum benefit from the irrigation system. As intensive growing systems are often developed in phases due to the capital costs involved, a long term partnership between grower and designer is needed to ensure smooth and sustainable implementation of irrigation infrastructure across phases. By: Isobel van der Stoep, Cherry Irrigation