E.C.made easy

There is an absolutely huge vocabulary that comes along with being a gardener. E.C. or Electric Conductivity, P.P.M. meaning Parts per Million and T.D.S. which stands for Total Dissolved Salts are all terms that one must become accustomed to when entering the world of indoor gardening. If you have ever purchased or used a plant nutrient, then you have probably read E.C. or P.P.M. in the mixing instructions. E.C., P.P.M. and T.D.S. are all related to one another and can be converted from one to the next. The beginner gardener might know of E.C. and may use a nutrient tester to keep nutrient levels proper. But, most gardeners don’t understand how the levels of elemental salts and metals can affect the growth of the plant. This article is designed to give you the advantage of knowing why E.C. is so important. This knowledge will allow any gardener to take the guesswork out of feeding their plants. They say “give someone a fish, feed them for the day. Teach someone to fish, feed them for a lifetime.” I say “teach someone to garden, they will be happy for a lifetime.”
E.C. or Electric Conductivity is a way for one to accurately measure the level of nutrient in their solution. Other units of measure consist of P.P.M. (Parts per Million), T.D.S. (Total Dissolved Salts) or D.S. (Dissolved Salts), M.S. (Measured Salts) or C.F. (Conductivity Factor). The most accurate way to measure the level of nutrient in your solution is by measuring the E.C. This is more accurate because different manufacturers of different nutrient testers use different standard to convert from E.C. to the P.P.M. reading. Therefore, P.P.M. readings are inaccurate and confusing. To help, here is a conversion scale from P.P.M. to C.F. to E.C., which is modified from the version found in “Gardening Indoors” by George Van Patten.

EC MS/CM	Hanna 0.5	Nutrawand 0.70	CF 0
1.0	500 PPM	700 PPM	10
1.1	550 PPM	770 PPM	11
1.2	600 PPM	840 PPM	12
1.3	650 PPM	910 PPM	13
1.4	700 PPM	980 PPM	14
1.5	750 PPM	1050 PPM	15
1.6	800 PPM	1120 PPM	16
1.7	850 PPM	1190 PPM	17
1.8	900 PPM	1260 PPM	18
1.9	950 PPM	1330 PPM	19
2.0	1000 PPM	1400 PPM	20
2.1	1050 PPM	1470 PPM	21
2.2	1100 PPM	1540 PPM	22
2.3	1150 PPM	1610 PPM	23
2.4	1200 PPM	1680 PPM	24
2.5	1250 PPM	1750 PPM	25
2.6	1300 PPM	1820 PPM	26
2.7	1350 PPM	1890 PPM	27
2.8	1400 PPM	1960 PPM	28
2.9	1450 PPM	2030 PPM	29
3.0	1500 PPM	2100 PPM	30
3.1	1550 PPM	2170 PPM	31
3.2	1600 PPM	2240 PPM	32

Although using slightly different methods of converting E.C. to P.P.M, each brand uses the same principal to get the reading. A small current is sent from one electrode to another and the ability to conduct electricity through the solution is measured. This allows the gardener to know the ration of ionic salts, the main ingredient in nutrient solutions, to water. Pure water or distilled water has no electrical conductivity, but as salts and metals are added, electrical conductivity will also increase in proportion.

There are many factors that can affect the E.C. level in your reservoir and growing medium. The temperature of the nutrient solution can affect the ability of the nutrient tester to read accurately, but quality nutrient testers are factory calibrated to compensate for the temperature. For achieving accurate readings from non-calibrated nutrient testers simply let the electrodes of the tester reach the same temperature of the solution it is testing. This is easily achieved by letting the electrodes sit in the solution for about five minutes.
Factors that can affect the concentration of the nutrient levels can easily be controlled once they are understood. One such factor is the evaporation of water out of the nutrient solution. When room temperatures are high, water evaporates out of the nutrient solution. This will likely cause the solution to become over concentrated. This happens in both hydroponic reservoirs as well as plants potted in soil or soil-less mixes. When a potted plant is in a room that is too warm, the nutrient levels in the growing medium can spike because of water evaporating. Evaporation not only causes the concentration of the solution, but it will cause nutrient to be left behind and build up. Fast growing plants need anywhere from 500-2000 P.P.M. of nutrient in the water being given to them. If salt levels get too concentrated the internal osmotic system will reverse and plants will actually become more dehydrated.

The dilution of a nutrient solution is very common with hydroponic growers. Nutrient testers are a must with hydroponic growers who wish to achieve the highest yielding crop possible. Fast growing fruit and flowering plants in rooms of moderate temperature can deplete the levels of nutrient in the solution practically overnight. Testing the E.C. levels of the reservoir every day or two can allow the gardener the ability to keep the nutrient at optimal levels for growth or flowering.

The one downside to E.C. and P.P.M. meters is that they cannot tell the gardener exactly which elemental salts or metals are low or which are too high. In fact there are some ingredients that will not register on nutrient testers because they do not conduct electricity. Urea, which is 46% nitrogen and the chelates are examples of such ingredients.

There are many things that can be done to limit the possibility of your nutrient solution diluting or becoming too concentrated. The first tip is to start with a quality nutrient. Quality nutrients are made to prevent the possibility of salt build up. Any nutrient that is in only one part will have some sort of anti-binding agent in it. These chemicals are used to keep the ingredients of the nutrient from binding with one another. The plants do not use these anti-binding agents and as a result a crusty build up will appear on top of the soil or soil-less mixes or rockwool cubes. Nutrients that are separated into an A part and a B part will not contain these anti-binding agents.

One way to maintain that your reservoir contains the proper amount of nutrient is to test the E.C. often and to change the solution in the reservoir completely every 4 to 7 days. Topping up the nutrient level in between reservoir changes will ensure that the plants always have the right amount of food. But some gardeners get lazy and won’t change the solution in the reservoir once a week; instead they top it up when needed. This is risky because even though the amount of nutrient in the solution may be correct the amount of each elemental salt or metal is unknown. Levels of a certain elemental salt or metal could become toxic if the plant isn’t absorbing all of it up.

As for soil or soil-less potted plants an easy way to maintain the proper E.C. is to water the plant enough to that 1/3 of the solution drains out the bottom. This will ensure that any salts or metals left behind from the previous waterings are washed away. Even if you are using a premium nutrient, it does not hurt to water your potted plants with straight pH balanced water every third watering.

There is an easy way to prevent water in your reservoirs from evaporating. If you cannot lower the temperature of the room then try covering your reservoir with black and white plastic. With the white side up and black side down the light will be reflected away from the solution helping the water from evaporating. This will also keep light off the solution and in turn stop the growth of algae and bacteria.

If you are gardening and you suspect that there may have been a spike in the nutrient levels, you should empty the reservoir of the nutrient solution and replace that with a clearing solution. Clearing solutions can also be applied to potted plants if the grower suspects a nutrient toxicity. Clearing solutions latch on to salts in the plants as well as in the growing medium and leech the salts out. Many gardeners will use clearing solutions only at the end of the fruiting or flowering cycle to purge the salts and improve the taste of the final product. But by having a clearing solution on hand, one could save a crop from toxicity when it seems to be doomed.

The amount of nutrient in the solution that is fed to a plant is an important as the quality of the nutrient. Too much of one or too little of another and it could mean the end for your plants and all the hard work involved. There is nothing to worry about when you’re next mixing a nutrient solution. Whether it is E.C., P.P.M., T.D.S., etc, with some knowledge and understanding anything can be made easy.

For more information on related topics please visit www.hydroponics.com.

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