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Old 10-27-2009, 02:47 AM
Luches Luches is offline
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Quote:
Originally Posted by Errol View Post

Just a quick rattle of the cage!
You're always welcome!

Quote:
Crop demand for nutrients changes through the season. Small amounts of nutrients are needed early, then the demand increases as the crop grows, especially after several clusters of fruit have been set on the plant. A common problem comes early in the season when plants become too vegetative (bullish) from too much N. The bullish growth distorts the leaves and stems, causing cracks and grooves in the stems. These openings are excellent entry ports for decay-causing organisms such as soft rot. Bullish plants usually produce misshapen fruits often with significant amounts of blossom-end rot and cat-facing. Keeping the N level low (60 to 70 parts per million) early in the season helps eliminate bullishness.
Quote:
Originally Posted by Errol View Post
Does this mean that one should maybe keep EC down around the 0.9 or 1.0 mark until the plants begin to show signs of fruiting? I've had the occasional case of blossom end rot in tomatoes, but it's never been a real problem. I'd be interested in your comments.
I don't agree with what is said (by whom ever) in that quote, because it's in fact very contradictory. I guess it's a combination of a false cause and a slippery slope: "if I reduce nitrogen from early growth stage, I'll not deal with BER later" is just a logical fallacy par excellence. The sun doesn't go down because we've turned on the street lights either, or does it?

1. First of all, we falsely believe (sometimes) that plants always take up what we feed them with a nutrient solution, just like chicken, cats or dogs. But osmosis is more complicated than mammal feeding and digestion. Plants take up a. what they need, b. choose from what there actually is in a nutrient solution, - and finally c. what the process of (rather complicate) osmosis allows them to take up in condition X. But In case there is too little nitrogen in a solution, plants my take it up very quickly and perhaps the PH will change and the nutrients will be unbalanced. That's what will happen basically and repeatedly...

2. BER is not caused by bullish growth all along the season or over time, but actually happens only A. with fruiting stage B. due of a lack of adequate calcium transport (which could either be caused by a actual lack of Ca, or a problem due to immobility of Ca.) and finally C. due to high temperature which leads to high plant metabolism and excessive vegetative growth. What actually happens when BER occurs, is that due to (temporary or sudden) heat, plant metabolism increases drastically but the immobile element Ca isn't transported and delivered quick enough to the tomato fruit. Bullish- or excessive vegetative growth itself is (or can be) partially responsible though, as huge amounts of N and Ca are consumed here. And hence there is not enough (slow moving) calcium available (left) for a healthy development of the tomato fruit.

3. Nitrogen levels as low as 60-70 ppm in the early season (as quoted) do not prevent BER for 2 reasons. A. most of the calcium provided in any nutrient solution comes necessarily from calcium nitrate. Thus, to provide enough calcium, we anyway need to keep Nitrogen at a certain level. B. BER doesn't happen at the early state nor in the middle nor later, but actually only when fruits are developing. That is why (as far as N-levels are concerned) we need to not exceed 150 ppm at any time - but actually neither at fruiting stage.

4. To prevent BER with tomato, the nutrient solution has to:

A. not exceed Nitrogen levels of 140-160 ppm during any stage
B1. contain enough calcium (140-160 ppm) all along.
B2. Supplementary calcium can be provided (max 0f 15-20%) through CaCl
C. temperature has to be kept under 34- (max 37°C) for best oxygenation and uptake (of calcium)
D. PH should be (especially at fruiting state) around 6.5 or slightly over (also for best uptake of calcium which decreases gradually under 6.5).

5. One generally tends to confuse concentration of a nutrient (EC) and ppm content of each element. Imagine an Energy Drink that is too sweet for your taste. You would simply dilute it 50/50 with mineral water but actually drink only one glass (half of it) - what will you get? Half of the sugar (or substitute) of course, but also only half of the sodium, magnesium, potassium and all other salts and trace elements. As a sub-consequence, your lack of minerals in your "system" would not be topped up adequately, but only get half as much as recommended by nutrition science!

Have a closer look at the chart I provided earlier (in another thread) and which describes a rather low feeding, step by step feeding strategy worked out by research at the University of FLORIDA (not California).


Now take the 5th cluster formula and cut it in half (as in using half strength) . You'll end up with 75 ppm of Nitrogen, but only 75 ppm of Ca, 25 P, 25 Mg and half of the Fe and all other trace elements. And while N-content may be OK for seedlings and small plants, all of the other will simply not be sufficient for very long!

I know this is kind of a cross between a no-brainer and high level nutrient science, but that's actually how it looks and finally works!

Appendix:
1. Tomatoes that are grown in cooler climates or kept cool with artificial help are less prone to BER, because very high metabolism and too excessive growth (due to heat) are less to be expected.

2. Calcium supply can be supplemented with foliar spray of CaCl as a preventive cure while the use of foliar spray as treatment (in case of outbreak) cannot actually cure BER.

3. Some strategies prevent excessive growth by pruning lateral shoots and even other parts of the foliage. It is said that only the foliage located close to the fruit cluster can deliver (or complement) nutrients to the fruits, - any others are actually useless from a physiological point of view. Which is certainly true for calcium anyway, as it moves too slowly (as learned earlier).

4. Some tomato cultivars are more prone to BER than others. There are even special greenhouse varieties (Holland) that tolerate extra high feeding (with much higher Nitrogen levels as well) and "bullish" growth and heat, without being affected (easily) by BER. Unfortunately these varieties tend to lack other qualities like originality or taste.

Last edited by Luches; 10-27-2009 at 09:35 AM. Reason: corrected FLORIDA (from California)
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