THE EFFECT THAT THE AMOUNT OF LEACHATE OBTAINED IN POUR THRU TESTS AND IRRIGATION HAS ON PH AND EC READINGS^©

Nutritional problems of container-grown plants are very common in greenhouses and may go undetected for prolonged periods of time (Iersel, n.d.). Over and under fertilization might result in reduced plant vigour and make them more susceptible to diseases and insects. Two important measurements that can be collected are the pH and the electrical conductivity (EC). The pH is a measure of how acid or basic the growing medium is, on a scale from 0 to 14, and it is important since it affects the availability of micronutrients in the growing medium (Iersel, n.d.). Electrical conductivity is a measure of the total amounts of salts in the growing medium, and it can be used as an indicator of the presence of macronutrients (Iersel, n.d.).
For the past years, Gro-Bark has worked closely with its customers in testing the growing medium of container-grown plants and checking its pH and EC. These field tests are conducted on a 3 week rotation by performing a pour thru test on selected crops and recording their pH and EC levels. The idea behind the pour thru method is to pour distilled water on top of the growing medium, collect about 50 ml of leachate and measure the pH and EC with a calibrated Hanna® pH and conductivity meter. Gro-Bark prefers this method because of its simplicity, inexpensiveness, and rapidness. Even though it is well known that this test is ideally done 2 h after irrigation and that over-leaching should be avoided, it is still unknown to Gro-Bark how much these two factors affect the accuracy of pH and EC readings. Therefore, the purpose of this trial is to investigate the effects that two factors have on pH and EC readings: (1) the amount of leachate obtained in pour thru tests and (2) the irrigation time. Having a better understanding of these two factors and their effect on pH and EC readings could provide some insights for Gro-Bark into how their pour thru tests can be improved.