Thread: PH Down ??
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Old 08-25-2011, 07:55 AM
GpsFrontier GpsFrontier is offline
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Location: Lake Havasu AZ.
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Quote:
SO your saying my plants should be drinking roughly 10-20 gallon's of water a day?
It's not that they "should," just that they "could" under the right conditions. One persons 6 foot tomato plant may have 4 times more foliage than someone elses. Each leaf transpires (exhales water vapor), so 4 times more leaves will transpire 4 times more water. As the plants transpire and exhale water vapor, they suck up water through the roots to replace it. So the amount of foliage is a huge factor as to how much water your plants use. Also not everybody's tomato plants have the same amount of fruit, the fruit sucks up a good amount of water as well.

That's even before you factor in the environmental conditions like temperature, humidity, amount of light, and even co2 level. All have an effect on plant growth, as well as how much the plants transpire. 68% humidity is a good level for tomato's. Here where I live our relative humidity is normally below 20% (without a greenhouse), unless we're having monsoons, then it could go as high as 30%-50%. As a result, your same plants would transpire a lot more here due to low relative humidity. I have had 4 foot tall, and 4 foot wide tomato plants drink over a gallon of water (each) daily. And that was without a heavy fruit load, but low humidity, and air temps over 100.

And 88 degree air temp is fine, though around 82 or 83 would probably be just about perfect (depending on variety). Though 88 degree water temp would be a big concern for me. Plants abort fruiting with high water (root zone) temps, and the fruit that had started generally are poor size and quality. Though there are heat resistant varieties that would probably be able to handle heat stress better.

Quote:
At most i'm only having to add maybe 4-6gallon's at best.
In a system holding 30 gallons of nutrient solution, adding 4 gallons a day you wind up replacing 100% in a week (about 13% daily). At 6 gallons a day you wind up replacing 100% in 5 days (about 20% daily). As the plants get bigger (if they do) they'll continue to use more water daily as well. I don't know if this is an issue yet because I don't know if there's a regular pattern between how much your pH rises, water use (levels), and/or EC/TDS/PPM readings yet in order to compare them.

But regardless if there is a noticeable pattern or not, 30 gallons for 10 tomato plants is about the minimum water volume you would want for each plant. It comes out to 3 gallons a plant, and the minimum recommended is about 2.5. Personally I would want about twice the minimums for large tomato plants. Not necessary when their smaller, but when they get bigger and begin drinking up more water and nutrients, That's when I would want a larger volume of water for slower fluctuations as the water level drops (from plants drinking it), and rises (from me replacing it), and thus maintaining a more even balance of nutrients and pH for the plant. Not to mention less fluctuation from nutrient depletion.

Quote:
And i think i understand what your saying, i should take my reading's at 30gallon's. Next morning fill my tank back up to the 30gallon mark and then check again?
Yes, though adjust the pH of the fresh water before adding it to the nutrient solution (to keep the test results even), but also cycle it through the system first to let it mix with all the nutrient solution in the buckets, growing medium, tubes etc. (again for accuracy), then take the reading when it's thoroughly mixed. If you can, add the water and take your readings at the same time every day. Keep a log of all your readings, and note when you do nutrient changes, if you add anything to the nutrient solution between changes. Also make notes of how much water the plants are drinking, if there is any EC/TDS/PPM changes (of course pH as well).

If adding water and taking readings in the morning, I would also keep a second log and take the same readings later in the day after the water level has drooped, and without adding any (again at the same time every day if possible). Basically log everything, and make it a science experiment. Eventually you should be able to see a pattern between the pH rising and other changes.
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