White Widow auto. End of 11 weeks from seed in ground. Soil FFHF + FFOF + Pearlite. Indoor grow. Temps 80 degrees, 45% RH. Light 800 - 1000 PAR. All in flower, several already flushed for harvest over the next week or two. Others may take three weeks or so. All plants look healthy and happy.
Do I need to flush out the non-flushed plants because ppm is so high? They are about three weeks (or more) from harvest.
What should I learn from this data?
Non flushed plants got:
Flowertime Nutes and CalMag at 6.2 pH going in and 30 ppms.
Not yet flushed plants – some really high ppm #s. Water out/ppms out #7 6.1/3800 ppm #8 6.2/2800 #4 6.4/2300 #2 Zebra 6.2/2845 #5 6.3/3200
Flushed plants – all under 2000 ppms. Water out/ppms out #10 6.2/1300 #6 6.3/1976 #9 6.2/1850
Yep I water/feed to run off every time. I’ve been told by a guy who I trust implicitly, that trying to react to ppms in soil is about impossible because we just don’t know if the tds readings are impacted by the dirt in the runoff.
Increasing runoff PPM means the plants are taking in less than you are giving them. This also coincides with the decreasing pH. Nutrients / salts are building up in the rootzone. For me, over 3000 PPM was usually not an issue. I paid more attention to the pH side.
If you are that close to harvest, I am thinking back off on the feed ppm - maybe 50%, and use a higher pH like 6.8 - 7.0. Also have more runoff than normal.
Hopefully this will wash out some of the excess while providing a higher pH late in flower.
Regarding pH & ppm
when I transplant into final containers I get a good amount of runoff. I use it and the next couple as a baseline to gauge where the numbers go later on. My pH rule of thumb was if it changes more than .5 I take corrective actions. I start with mini flushes like I described above (basically overwater to create more runoff)… If the numbers do not change enough, I will flush.
These are pH charts.
If following Kootmed 6.2 is slightly out of range on the low side.
According to growweedeasy it is in range but still on the low side.
I would try to raise it a bit like @kellydans and I described. Feed with a higher pH than you have been using and produce more runoff then normal. Basically trying to raise pH and lower ppm using a light hand rather than flooding it this far along.