For optimal climate control, accurate and reliable measurements are of course very important and maintenance to the CO2 box should be standard on every farm.

First thing would be to check the tubes and the magnetic valves for leaks. If valves are leaking they need to be replaced immediately as they will cause mixed air in the tubes.

All the tubes can get condense inside and block the air flow, also causing mixed air going into the CO2 sensor and sending the wrong value to the climate control computer. You can avoid this by blowing the tubes out regularly with an air compressor to avoid condense to gather inside them. Especially when tubes are not placed correctly and have no filter at the end of the tube this will happen easy.

A good practice on every farm would be to check the reference measument value on your CO2 system daily. That value is the CO2 measured in your outside conditions which is either outside, in the central duct or wherever the outside measurements sensors and CO2 tube are placed. The ppm value depends on where it is placed but should be consistent and seeing inconsistent value there can be a first indication that there is something wrong with your CO2 meter and some maintenance is needed. A good portable, calibrated CO2 meter can be a great help and indicator. You can detect problems before any misreading’s will cause more damage than necessary.

When all the tubes are clean and no leaks are detected the CO2 meter needs to be calibrated using a zero cartridge for the low values and CO2 calibrated gas for the higher values. Ask your supplier for the exact instructions.

Erik de Groot
Global Agriculture Services
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A good climate control is of course vital for every mushroom grower even more if you want to stand out with the quality of the mushrooms. One of the most asked question I get as consultant is: How can we get better quality and how can we keep the quality of the mushrooms good until the end of the flush? Now, of course the quality at the end of the flushes will always be less than at the start, no illusions there. But improvements are always possible and most of that you can get from an ideal climate.

Before we had more advanced climate installations with more options, we always controlled the rooms on Air temperature, Relative humidity and CO2. However, with the new systems coming on the market there is a lot more to learn than we think and controlling rooms, especially in harvest stage, on moisture deficit, inlet moisture control and even measuring systems for evaporation are used.
To understand the difference between all the systems you need to know exactly what the Mollier Diagram stands for and if you manage to run the system well you will see advantages, especially in quality of the mushrooms. The Mollier Diagram is crucial in mushroom growing and climate computers make the changes in the room based on that Diagram with the Absolute humidity (AH) as the biggest factor. Let’s me explain a little bit more about of those controls, the moisture deficit.

As we are changing air temperatures in the flushes you will see in the Mollier Diagram that that will create differences in evaporation as we change the temperature but leave the RH the same, with other words, we change the AH. By controlling on moisture deficit we will maintain a constant evaporation, what will benefit the quality of the mushrooms, no matter what the temperature differences are. The computer will calculate the right RH for the current air temperature, to keep the same evaporation in the growing room.

Moisture deficit is the difference between the current absolute humidity in the room and the maximum possible absolute humidity at the same air temperature. Once this value is constant the evaporation capacity of the air is also constant.

To use this in a practical situation of course first of all you need a climate control computer that supports the moisture deficit system and change it from RH to moisture deficit control, in the computer that will be named as Absolut humidity control. Ideally this is linked with humidity control of the inlet air to get the best benefit. The mushrooms will have a constant evaporation and that will benefit the quality as changes in evaporation will disturb their growth. The mushrooms will get less water stems and go softer in a later stage what would give an extra picking days benefiting the yield as well as quality.

I recommend to change the computer 1 day before you start harvesting the flush from RH control to moisture deficit control. When you changed the control, set the AH in the computer so that the RH is at the same level as you normally run it in the flush. So if you normally run the flush on 17.5 degrees and 89% RH, keep the air temperature the same and set the AH so that he calculates the 89% RH as set point. Keep 0.2 difference between minimum and maximum AH. From that moment forward you let the computer calculate the right RH and change the air temperatures as you normally do, until the end of the flush. After the flush put the system back to RH control.

The only way to find out is try other controls to improve quality. Many option are out there and based on results on other farms worth trying. If you start and are seeing any improvement? Learn more and keep doing trials, good luck.

Erik de Groot
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