HYDROPONIC
ELECTRICAL
CONDUCTIVITY :
EC and EC Meters Explained
by Grubbycup
Mother Nature doesn ’ t make mistakes , but people do , so monitoring EC is essential for any hydroponic grower .
Electrical conductivity ( EC ) meters are used to estimate the amount of nutrient ions in a nutrient solution . They rely on the principle that solutions with more ions conduct electricity better than those with fewer . Although the exact specifics of how each meter performs the test may differ , the basic concept is the same . All EC meters test how well a given solution conducts electricity . Pure water is not a particularly good conductor of electricity . To reflect this , EC meters will show a reading of zero ( or at least ideally zero , some meters have trouble when there isn ’ t enough conduction ) when placed in pure water . Water with conductive contaminates in it ( for example , the ions from salts ) do conduct electricity , and that difference is where EC meters come in . Nutrient solutions are created by dissolving measured amount of nutrients ( often salts of nitrogen , phosphorus , and potassium ) into water ( the solvent ). Hydrophilic ( waterloving ) materials like salts tend to dissolve easily in water because water molecules have a positive charge on the side with the two hydrogen atoms , and a negative charge on the oxygen side . These are attracted and attach easily to many other molecules . Salts are often used as nutrient sources because they also have a positive and negative side but are generally held together with a weaker ionic bond . Water molecules attach themselves to either side of the salt molecule and literally split them apart . That ’ s why many chemical hydroponic solutions make use of nutrient salts dissolved in water . When salts such as potassium nitrate are dissolved in water , they break into their ionic forms . In the case of potassium nitrate this breaks into ions forming the cation K + ( potassium ) and anion NO 3- ( nitrate ). Not only is this handy as a source of both potassium and nitrogen for the plants , but it allows the solution to better conduct electricity . There are many salts that can be used as fertilizers , such as urea , ammonium nitrate , mono ammonium phosphate , diammonium phosphate , and potassium chloride to name a few . The more salts that are added to the solution ( to a point ), the better the solution conducts electricity , and the higher the EC will read on the meter .
Raising the temperature of the solution increases the movement of its molecules , including its ions , and raises its conductivity . As one of the factors of conductivity is temperature , some EC meters include a thermometer to adjust their readings automatically , or one without can be used if care is taken to measure samples at the same particular temperature each reading or with the use of a temperature-conductivity adjustment chart . One place where EC can be immediately useful is in determining if a solution is within expected tolerances . If the EC numbers unexpectedly double in a fresh batch of nutrient solution , it may be an indication that nutrient concentrates were added twice . Paying attention to EC levels can not only help identify issues but can be used to track changes in a nutrient schedule which can then be compared with similar historical data recorded from previous seasons . In general , nutrient schedules start light , then build in intensity to a plateau , and then taper off as harvest approaches . Careful recording of readings during one season can set a baseline to compare subsequent seasons against , possibly alerting an attentive gardener to potential issues or unexpected changes . Note what nutrient schedule was used for the week , and the EC of the nutrient solution . This way changes in the nutrient schedule ( or other factor ) can be compared to prior performance . Changes that can be linked to improvements can be kept , and detrimental changes can be reversed . This allows for a continuous fine tuning of the nutrient regimen . While EC meters do a fair job at displaying how many ions are in the solution , they don ’ t indicate which ions are in the solution and it will not show results for any particular nutrient . A solution high in nitrogen salts but low in phosphorus may give an EC reading of 2 , but so can one low in nitrogen but high in phosphorus . A solution made with table salt may show an EC of 2 but still not have enough nutrients in it for plant growth because plants don ’ t need much chlorine and need even less sodium . A different solution with an EC 2 value might be well suited to growing plants if the ions are part of a balanced mixture of macronutrients and micronutrients .
24 Maximum Yield