Equipment Every Greenhouse Should Have
by John Erwin
Professor, Department of Horticultural Science
University of Minnesota
How many times would you like to know your pH and EC immediately to decide what to fertilize with at that moment? What is your plant temperature? Is your media temperature what you think it is? Do you have a virus in your crop? Are your lights positioned to give you the amount of light you need for night break lighting or supplemental lighting? What temperatures did your plants get exposed to during shipping? New instruments available on today can answer these questions.
Soluble Salts Or Electrical Conductivity (EC) Meters
EC or soluble salt meters measure how much salt is in the media. Why is this important? Too much media salt will result in water actually leaving the roots and moving into the media. This will result in root burning and eventually result in root death and rot. Where does the salt in the media come from? In greenhouses, salt in media comes from two places: water, and fertilizer – fertilizer is a mixture of salts. Fertilizing or watering, without leaching, will result in increasing media salt levels that will eventually result in soluble salts burn.
Aside from measuring when salt levels are too high, EC meters are great ways to determine if your injector is working the way you think it is!
http://en.wikipedia.org/wiki/EC_meter
Where do you buy one?
EC/Soluble salts meters are inexpensive and very reliable. EC meters come in three different uS measurement ranges: Low (0-199 uS), medium (0-1999 uS) and high (0-5.0 mS or 0-19.99 mS). In general, most greenhouse companies should purchase the one that is in the high range (0 - 5 mS or 0-19.99 mS). Also, you should purchase a meter with accuracies of + 0.02 and resolutions of 0.01 mS. Calibrate EC meters using a single standardized solution that you can buy premade, or make yourself using distilled water (follow directions) and mixing in a packet that you purchase. Regardless, choose a standard that is near 1.41 mS as that is a reading which is similar to what you will be measuring in greenhouse media.
EC/soluble salts meters can also be in the same probe as pH meters, i.e. they are combined probes and have a pH meter and an EC meter. The problem with a combined probe is that if one part of the probe breaks, you need to purchase a whole new probe even though the EC part of the probe may be fine. I recommend having two probes that you can connect to the same meter, or just having two meters. The following list is a list of sources for EC meters:
EC METER SOURCES:
Cole-Parmer:
http://www.coleparmer.com/catalog/product_index.asp?cls=555
Gempler’s:
http://www.gemplers.com/list.aspx?SKW=ec+meter&src=24GLHTB
Hanna Instruments:
http://hannainst.com/usa/subcat.cfm?id=003
Milwaukee:
http://www.water-testers.com/
Myron Instruments:
http://www.myronl.com/products/ds_pds.htm
Omega Instruments:
http://www.omega.com/toc_asp/sectionSC.asp?section=EE&book=green
Spectrum Technologies:
http://www.specmeters.com/Conductivity_Meters/ |
