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variations on the theme, such as rotating pipes, moving pipes and drip irrigation systems, were also investigated and tested. The under-bed system of pipes – that is a common watering system today – was also looked into, but absolutely failed to meet the required standards, partly because water distribution was poor at low pressure. In the mid-1990s, the first computer controlled cable-pulled systems became popular signifying a revolution on many farms and attracting world- wide attention: no huge volumes of water required, control over the spray nozzles and working pressure of the water.


Pipes and fl exible pipes In 2005, the pipe watering system made a reappearance, but this time with working pressure of around 3 bar, so the mist could be dispersed over a far larger surface area, but about half the water was wasted. A required pump capacity of 40/50 m3/hour is no exception. If more copious watering is involved, such as 3 l/m² this is feasible, but when less water is needed, such as 1 or 1.5 l/m², the water distribution is poor. There is also no way of checking if all the nozzles are functioning properly and problems are only detected afterwards – entailing consi- derable financial risks. In addition, in systems where the pipes are emptied the actual amount of water applied to the beds can widely fluctuate, and there is a higher risk of soiling in the nozzles. Leaving water in the pipes increases the risk of legionella (as water can be left in the pipes for one to two weeks at summer temperatures in excess of 25 degrees Celsius).


The ‘new’ system with flexible pipes has been studied many times in the past (particularly by the University of Wageningen). There is now another system with flexible pipes on the market. I think it stands a good chance of working well, if it wasn’t just an extra system alongside the existing systems (see article in MB76). I can’t imagine that growers would be prepared to invest in this system on


existing farms. Perhaps it is more viable in new - build projects, where subsidies can be applied for.


There is also a far greater risk of spreading disease, including bubble. To prevent transmitting diseases from one room or farm to another, much more effort has to be put into disinfection, not just of the flexible pipes but also all the accessories such as winches used by the grower and filler and so on. Many growers are already reticent about taking spray lorries from one growing room to another. If the investment really can generate 3 to 4 kg/m² extra of good quality, the maths is easy, but I have my doubts. The increase infection risk at filling and more labour at filling, emptying and cleaning/ disinfection also have to be factored in. The matter of monitoring also has to be considered: is enough water being distributed evenly over the beds? If the answer is no, it’s already too late. Despite this, it’s of course good news that new systems are being developed. The same applies to using compost as a growing medium or picking robots. At the moment making sure you use good quality compost that can produce another 2 to 3 kg/m² extra is just as important. Compost with the right level of activity will give more and better quality mushrooms with less risk of bacterial blotch.


Good watering is worthwhile! It is crucial to water properly at the right time. There are still many growers who water after all the other tasks have been finished –picking first, then cleaning and maybe watering in the evening, when actually the beds should have been watered in the afternoon. So what do measures such as good watering achieve in the form of extra yields of 1 of 2 kg/ m²? As an example, we will take a farm with 12 growing rooms of 300 m² with nine flushes. One kilo extra is 300 x 9 x 12 = 32,400 kg at € 1.25, which converts to € 40,500 per year. There are naturally other influential factors such as the compost, but growers can control their watering strategy. The financial benefits including picking costs are € 25,000 - € 30,000.


Good water distribution over the beds, leading to harvested mushrooms of a higher quality, can result in lower picking costs, a better price of e.g. € 0.05/ kilo. With a yield of e.g. 30 kg/m² on the same farm used in the example with nine flushes this converts to ± 300 x 30 x 9 = 81,000 kg x €0.05 = € 4050/room per year. With 12 rooms this amounts to € 48.600, while with rooms of 400 m² this rises to € 64,800 per year.


Hedonk spray arm and nozzles.


It is certainly worthwhile getting good advice on systems, settings, working pressure and how to clean nozzles for example. The nozzles should be replaced in the correct position and settings such as working pressure are extremely important to obtain good results.


Henk Douven has worked in the mushroom business for more than 45 years, for a long time at Dofra (the company his father founded). In 2011 he started his own company Hedonk, which provides consultancy but sells complete watering systems and parts, spraying arms and nozzles as well. For more info: www.hedonk.nl, info@hedonk.nl


 MUSHROOM BUSINESS 15


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