Influence of Time on Measuring Container Fertility by the Pour-through Extraction

Research was conducted to compare the traditional pour-through (PT) extraction procedure of waiting two hours following irrigation to that of waiting only thirty minutes following irrigation to make electrical conductivity (EC) and pH measurements.  It is believed that the time following irrigation, if consistent throughout the soluble salts reading for a given crop, will represent the available nutrient levels.  This has not been previously verified.  Recommendations for the time from irrigation to sampling vary greatly.  Thirty to sixty minutes has been recommended for greenhouse crops. Two hours and more is the standard delay following irrigation for woody species.  Lindera benzoin (L.) Blume were potted into straight pine bark media in 7 gallon containers and fertilized with medium recommendation for 7 gallon containers of 214 grams of Osmocote® Plus 15–9–12, 12–14 month.  The plants were placed in Top Hat™ Stabilizer Baskets on a gravel bed. Irrigation was provided via a single Tavlit 4463 sprayer delivering 15 lph per container by cyclic irrigation three applications per day for 10 minutes each application.  The two treatments (the 30 minute delay, and the 2 hour delay) were allocated to three rows (blocks) of containers in a randomized complete-block design.  Each treatment within each block consisted of 7 containers.  SAS was used for statistical analysis.  Pour-through extraction data was collected every two weeks from April 26, 2013 to September 24, 2013.  The EC and pH readings for the 30 minute delay and 2 hour delay after irrigation were statistically the same.  The pour-through results 30 minutes and two hours following irrigation enable a recommendation to shorten the delay between irrigation and the pour-through procedure.