This morning I added acid to all the float beds. I always find that adjusting the beds after having the water in them is difficult–the amount of biocarbonates in the bed seems to vary quite a bit, so sometimes I can add a lot of acid and make no discernible impact, other times I see a big jump.
Since it’s expensive and slow to send the water out for sampling I tend to kludge it: I add a (conservative) amount of acid, wait 24hrs, see how much the pH changes and repeat on all the beds that still need it until the adjustment is complete. Occasionally I overshoot and add too much acid, but usually this works out. I am sure that if my chemistry skills were better I could get a much more accurate measurement and do it all at once. (Please leave a comment if this is something you know about and could teach me to do better).
I noticed that the basil beds that I’ve been adjusting the EC down on over the last week or so are looking a lot better. They are actually improving noticeably everyday.
Here is what happened. A few weeks ago we started to see some chlorosis (yellowing) and severe dwarfing on the basil plants. pH was measuring about 6.0 to 6.2 (so not concerning) and EC was between 2.67 and 2.68–high, but not close enough to 3 to raise an alarm. Worried that we had a nutrient imbalance problem we sent in a tissue culture to a local lab and also a water sample.
The water sample came back first and showed a few odd problems, but the one that stood out was low iron. Although the chlorosis was not clearly interveinal (I usually expect iron to have yellow between the veins on the new leaves) it was on the new leaves and we calculated how much iron we were short and added that to the beds.
A few days later the tissue culture came back showing very high iron (above normal range by 300%) and other nutrients in a variety of positions. This is how tissue and water samples seem to be. You would think that you would get low nutrient x in the water and low nutrient x in the leaves and be able to adjust because of it. But it never works this way.
Our government greenhouse specialist happened to be travelling by and stopped in at our greenhouse to help to figure out the results. He said that the amount of iron in the tissue culture might be thrown off because we included too much stem in the sample and he thinks he read that iron tends to be higher in the stems (this could be as I gave whole plants to the lab as they were only at the 2-leaf stage). We spent an hour running through possibilities and then he sent it off to some scientists on our behalf. One suggested that he saw something like this that was solved with magnesium sulphate, but the numbers on our tests didn’t suggest a low in these areas so he wasn’t sure. The other said that he thought our EC was too high.
I must admit that I was sceptical about the high EC theory. We’ve grown basil at higher EC levels in the past without a problem. He said, though, that maybe the young plants were more susceptible to EC than older plants are and that our plants looked quite small. After this I (coincidentally) calibrated our EC meter and realized that it was reading quite low meaning that our actual EC was higher than I was realizing. Also, we have been putting in plants that are younger than we used to.
Note to myself: 1. I need to be less lazy about calibrating my handhold meter. 2. The younger plants need a lower EC than I expect.
The scientist suggested an EC of below 2 for the very young plants. I’m worried that that is too little, so we are aiming more for the 2.2 level. But even the 2.48 which I have in my highest bed currently is showing big improvements over the 2.58 it was last week and the 2.67+ that it had before. I’m seeing the green come back in the plants and hopefully that means that we’ve seen an end to our basil problems!
The next problem will be to figure out why my lettuce is growing so slowly, but hey, lets stop and celebrate one major victory!