Calculating Proper Runoff Numbers

meter callibrated? what is error% or +/- accuracy of tool? pH dropping can be microbes. This depends a bit on how well buffered your nutrients are and even your tap water pH. (or whatever water source). You probably want to target a slightly higher pH with soil. It gives a bit more room for error on the low side. You drop a few tenths below 5.8-6.0 and you can lock out some nutes very quickly. you aren't adding 1000ppm to 1000ppm (false perception). You don't want it escalating way over 1000ppm in nearly all contexts. Some living soils or super soils may have a valid arguement, but in genearl you don't want your concentration of dissolved nutrients spiking or even gradually increasing over time will also cause major problems but further down the road before you see it. You want to maintain a safe and fertile concentration and ratio (balance) of nutrients. This is the point of runoff. get 10-15% runoff and it should avoid any buildup of concentration. This runoff should go down drain or thrown outside. Don't let it soak back in to pot. This will maintain your pH too -- assuming microbial issues are not causing a wild swing in pH. some evaporation occurs between irrigations. this increases "EC" or ppm of the water soaked into the soil. The excess runoff during irrigation will average everything back out and the higher concentrations are flushed out. What you add is significantly more than what moisture remains, so it safely returns it back to what you feed. your soil has nutes in it. This is why you don't see it running out at 1000ppm. The plant isn't clawing and it looks pretty late into flower. While i wouldn't make any drastic changes at this point in time, i'd be careful of those ppms rising too high. Watch for any hint of burnt tips or leaf symptoms. if they start to pop up, maybe give 1/2 dose for a couple fertilliations and make sure that runoff ppm drops a bit. other note -- runoff won't accurately tell you what is in the soil. it should probably be a bit higher, unless you get a ton of runoff, at which point it may be damn near what you feed if enough fertilied water runs through it. It's a good thing to check and will hint at an impending problem, but don't read it as "my soil is 1700ppm" because that's not what it is telling us. it is likely lower than what runoff is. watch for relative changes.. is it going up? down? staying the same is more often the target if all is going well. 1.5EC or 750ppm is probably a better target for future. Soil is more complicated than that since you have some nutes in it and slowly ramp up feeding as the plant eats up what is pre-built into soil. there are many factors involved with soil to consider. if you stick in this range and religious about runoff and not having any dry pockets of substrate after any irrigation, it's virtually impossible to run into any nutrient issues. if you irrigate with water only, a little less runoff is fine. be religious about teh 10% when you fertilize, but any water-only irrigation you just want to ensure there are no dry pockets. this requires some runoff to be sure. Unless your intention is to lower concentrations of nutrients in soil, of course.. extra runoff can quicly do that in case of toxicity.