[joe fresh]

This isa little guide to the pour through method for testing soil and soiless media for PH and EC(salinity) to make sure they are in correct levels or if there is a problem.






The Pour Thru Method for Testing Container Media
Steps for the Pour Thru method



1. water containers to saturation (so that a few drops of water come out of the bottom of the container) with the normal irrigation water they have been receiving


2. after container has drained for one hour, place a saucer under the container




3. pour enough distilled (DI) water on the surface of the container to get 50 mL (1.5 fluid ounces) of leachate to come out of the bottom of the container (Table 1)


4. collect leachate for pH and EC testing


5. calibrate pH and EC meters


6. measure pH and EC of samples


Saturated media extract (SME)

SME is currently "the" method of testing soilless greenhouse media and it is almost universally done by commercial and university labs, including the UMass Soil and Plant Tissue Testing Lab. In this test a paste is made using soil and water and then the liquid portion (the extract) is separated from the solid portion for pH, soluble salt, and nutrient analysis. Special skills and laboratory equipment are required to perform this test. SME is probably not suitable for a grower to use unless the greenhouse operation is large enough to support a lab, a technically trained person is hired to carry out the tests, and there is a commitment to frequent testing and tracking of the results.
1:2 dilution method

This method has been used for many years and has good interpretative data to back it up. In this test an air-dried sample of soil and water are mixed together in the volume ratio of 1 part soil to 2 parts water (e.g., using a measuring cup, 1 fl. oz. of soil + 2 fl. oz. of water). The liquid extract is then separated from the solids using laboratory grade filter paper or a common coffee filter. The extract is then ready for analysis. This is a very easy test to master and quite suitable for on-site greenhouse testing of pH and soluble salt using meters available from greenhouse suppliers. The 1:2 method is a very good choice for occasional pH and soluble salts testing by growers on-site.





INTERPRETING TEST DATA EC (Electrical Conductivity)

The values that you measure for EC will depend on the method you use for testing the container media. EC guidelines for several horticulture crops are presented in the table




Problems with Low EC

A low EC means that your plants are not getting enough fertilizer salts. Symptoms can include stunted plant growth or leaf discoloration due to lack of nutrients. Nitrogen deficiency (yellowing of lower leaves) often appears first.


Problems with High EC

Excess salts can accumulate when: you are applying more fertilizer than the plant requires; the container media has a high initial salt level; leaching during irrigation is insufficient; or your water source contains naturally high levels of salts. Excess salts can cause tissue death. Symptoms often appear first on the lower leaves and appear as yellowing (chlorosis) or browning (necrosis) that begins at the edges of the leaves and spreads inward. High salts can cause root tips to die back; and plants may show wilting even though the medium is still moist. High salt levels have been shown to increase the incidence of Pythium root rot. Solutions to high salts include leaching with clear water, then cutting back on the fertilizer rate if that was what caused salts to accumulate in the first place.



pH

pH affects the ability of nutrients to dissolve in water (solubility). Solubility is important because roots can only take up nutrients that are dissolved in solution and cannot take up the solid form of the nutrient.



Problems with Low pH

In container media, the micronutrients iron, manganese, zinc, and boron are highly soluble at low pH (pH 5.0-6.0). Therefore, at low pH these nutrients are available and readily taken up by roots. If pH is too low, typically below 5.0 for most plants, the nutrients become so soluble that they may be taken up at harmful or toxic concentrations. A classic symptom of this is iron toxicity which appears as leaf bronzing and chlorosis which appear first on lower leaves. Certain plants that are especially efficient at taking up iron, such as seed and zonal geraniums and marigolds, can exhibit iron toxicity when pH is below 6.0.


Problems with High pH

At high media pH the low solubility of phosphorus, iron, manganese, zinc, and boron (see figure below) makes these nutrients less available to be taken up by roots and so deficiency symptoms can occur. Certain plants are less efficient at absorbing micronutrients (especially iron and manganese). These plants require a slightly lower pH to be able to absorb enough of these nutrients. A classic example of this is iron deficiency is petunia. Affected plants show yellowing between the veins on the upper leaves. Often there is enough iron provided in the fertilizer/container media, but the pH is too high for roots to absorb it.

[DevilWeedSeeds]

Good information. Thanks for posting.

[Bunz]

FWIW..................DI water isn't "distilled", it's deionized............it's been ran thru deionized resin which further removes dissolved solids not removed by the reverse osmosis membrane.

Good info nonetheless.

Bunz

[rives]

Interesting stuff, Joe. I ran across that testing protocol quite a while ago and have been using it since. The charts for ec and pH look a little odd to me, though. I try and keep my soil-less media (SS#4 based) around 6.2-6.5, and the ec chart looks higher than hell to me (2.6-4.6=Normal). Any thoughts?

[joe fresh]

the chart is for runoff only, these are the acceptabe ranges for moderately salt tolerant crops, which cannabjs falls under....

notice the pourthru method givesthe widest range, imo this is because it is the least accurate compared to SME or 2/1 method...imo the less "range" means the more accurate....

but this info is good, using pourthru method if runoff EC is anywhere between 2-6 is ok...but ime is best between 1.6 and 3.5...but this is strain and environment dependant and im sure there are variables we are not considering.

[inreplyavalon]

This is a great thread, thanks Joe. I have been playing around with runoff and the 2/1 testing methods in coco, and comparing the two. My results fall into the ranges on the graph. I used to flush when i would have a 3.0+ runoff reading, but instead started using the 2/1 testing method, and my EC was usually around .7-.9. Plants would be showing signs of deficiency and i was thinking they were overfed because of the high Runoff readings. This round instead of a flush, i increased nute strength and they reacted real well.
Growing is so humbling, empowering, and endless in its insights...

[IvAx]

Hi! Is there anyway of doing this in a more comfortable way weekly?
I cannot afford to saturate my plants medium weekly... Maybe some kind of measure device?

[Dave Coulier]

Originally Posted by IvAx

Hi! Is there anyway of doing this in a more comfortable way weekly?
I cannot afford to saturate my plants medium weekly... Maybe some kind of measure device?

Why its nice of you to ask, because I have just the item you are looking for. Hanna HI 83900 Suction Lysimeter. Its the best way to monitor EC/pH within your media without the need of flushing. Easier on the plants as well, and you can get daily values giving you so much more insight into whats going on down there.

*Ive since come to learn pH values are not 100% correct with using soil extraction method via lysimeter. The pH will be higher than that of the soil solution in the media. With that said, I still record my pH results since I can still make value of the results along with visual observations.

[sonofthebong420]

Great topic, im starting a new crop on soil and i started mesuring the runoff and saw 2.000ppm and started to freak out beacause they were still seedlings.
Now i see i did know how to measure and interpret the numbers. Thanks !

[Sante]

Really interesting!