Ask Erik - Organic Nutrients
Hey Erik,
Their seems to be alot of discusion about measuring organic nutrient strength use electronic equipment. It is a know fact that solid organic matter can effect the signal resistance from one point to the other on testing devices. It is expected that when measuring organic nutrients that the tds/ppm will generally be higher even thought nutrient levels are moderate. Has their ever been a conversion factor on testing organic nutrients?
Will
Thank-you for your question.
I do not believe that attempting to measure EC or PPM with electronic dissolved solids testers would provide an accurate reading of organic based nutrient values. There is particulate in the form of dissolved solids in most organic solutions and will provide some electrical interference to provide a reading. However, this reading is not indicative of the nutrient value contained in the organic solution. Also with soil/soilless based organic production, there are micro-biological organisms which play a strong role in the availability of nutrients to the crop.
Typically, most testing facilities will perform chemical reactions versus electronic readings to determine actual quantities of the individual available nutrients in an organic fertilizer solution to verify and confirm stated nutrient values. Remember that many elements are present in the solution, so electrical testing would only reflect them as a group, not individually.
To give you an idea of how much of what nutrient is in your applied nutrient solution, you can work backwards mathematically from the fertilizer's stated levels. For example, if the label states the nutrient contains 2% nitrogen, it means that there is approximately 20 000 PPM (mg/L) of elemental N in the solution. If you apply one teaspoon per litre (5ml/L) to your reservoir this will dilute it to approximately 100 PPM of elemental N ((5/1000) X 20 000).
However, you must remember that fertilizer labelling laws are archaic, as plants will use Nitrogen (N) in either Nitrate (NO3) or Ammonium (NH4) forms so this figure is only truly representative of potential plant usable nitrogen. Typically, following the manufacturer's feeding guidelines will supply the necessary plant elements in their ideal ratios and concentrations.
Cheers,
Erik Biksa