Afternoon watering... a disconnect

[keithrs]

Ray said it..... Interesting thread!!!

 

[keithrs]

Along the line of air movement at night decreasing the chance of disease when foliage is wet....

As air moves across the wet leaf the water evaporates. As the water evaporates the remaining water is cooled. The cooled water will absorb more oxygen from the atmosphere. Water with more oxygen will have slower pathogen growth. Now add in the cooler water temperature and you have even less pathogen growth.

I tend to agree with this...

Anaerobic bacteria thrive under moist stall air.... Hence anaerobic... Some growers tend to use too fine or allow there mix to break down too much, there for 'sealing' there roots off from air movement allowing 'bad' bactria too take over.

I like to believe that introducing aerobic bactria and to some degree fungi that 'eat' anaerobic into a greenhouse is beneficial along with very good air movement around the roots.

Water holding to air capacity is super important for long term health of your roots.

EDITED FOR SPELLING****

 

[Rick]

I think the reason that a lake's overall oxygen content increases is because the turbulence brought about by the wind stirs the water, bringing the lower-content stuff up from below so it can become more oxygenated.

As Chris said, the low surface-to-volume ratio of a lake will slow the "re-equilibration" process, but if things stay calm, it will return to the overall average dictated by the conditions.

As noted above in a couple of posts lake/pond DO levels are all over the place, and a function of depth, temp, elevation, clarity (for light penetration to support photosynthesis), TDS. Typical surface DO's are full saturation or greater based on pelagic algae photosynthetic rates. Lower depths can be deoxygenated, and the demarkation can be abrupt. Otherwise known as the thermocline. Thermoclines are seasonal and can be disrupted or shifted by winds.

http://en.wikipedia.org/wiki/Hypolimnion

But breezes generating mild ripples have very little effect on overall DO content of lakes and ponds. But very little of the above has much to do with DO levels on damp leaves (or leaf axials).

Also as noted earlier DO saturation is mostly a function of volume/surface area/organic loading. Subsequently the DO levels in films on leaves is full saturation unless the leaf is already completed covered with a film of bacteria munching away on a film of organic (poop/sugar) media.

 

[Rick]

I tend to agree with this...

Anti-aerorobic bactria thrive under moist stall air.... Hence anti-aerorobic.... Some growers tend to use too fine or allow there mix to break down too much, there for 'sealing' there roots off from air movement allowing 'bad' bactria too take over.

I like to believe that introducing aerobic bactria and to some degree fungi that 'eat' anti-aerobic into a greenhouse is beneficial along with very good air movement around the roots.

Water holding to air capacity is super important for long term health of your roots.

Do you mean "anoxic bacteria"? Anoxic species don't kick in till less than 1 or 2 mg/L DO on thin film aqueous solutions, and you can't reach this level at normal atmospheric conditions without a tremendous organic load full of aerobes eating organic materials and using up the DO in the first place. I work in waste water systems using both activated sludge and fixed film systems, and the only way we can get the anoxic species to work under very heavy loaded systems (not the wimpy stuff on leaves in a GH) is to put the system in a full nitrogen environment to purge out the DO.

In general trying to blame the pathogen issues on oxygen content is not going to fly very easy since the conditions in our green house are still fully supporting normally oxygenated systems. (Nobody suffocates in their greenhouses at night).

 

[Rick]

http://www.fluidfertilizer.com/pastart/pdf/36p16-19.pdf

Check out the above article on plant nutrition and disease. Looks at Erwinia and Botrytus infections in bean plants relative to tissue calcium concentrations.

If you compare tables 1 and 2 and put in light of the antagonistic effects of potassium on calcium uptake you can see how excess K promotes loss of resistance against two disease genera that are common problems in orchids.

 

[keithrs]

I meant anaerobic bacteria.

 

[Rick]

I meant anaerobic bacteria.

http://answers.yahoo.com/question/index?qid=20070622060405AAPb3YW

The above is good for the fast answer.

 

[Rick]

I tend to agree with this...

Anaerobic bacteria thrive under moist stall air....

EDITED FOR SPELLING****

Afraid not. Moist stale air still has too much O2 to support obligate anaerobes.

Even the exhalation from human lungs still contains enough O2 to support aerobic bacteria. Minimal DO for supporting fish in EPA tox tests is only 4ppm. Aerobic activated sludge waste water plants typically run between 2-4 ppm of aqueous DO to minimize blower costs. From 1-2 ppm DO the falcultative anaerobes start to wake up. The obligates won't get happy until 0 mg/L. The crazy sulfur bacteria and methangenerators can't kick in until the sulfide concentrations build up to significant levels and drive ORP to crazy negative values. Sulfides can't exist in oxic environments without getting converted to sulfates.

 

[Stone]

http://www.fluidfertilizer.com/pastart/pdf/36p16-19.pdf

Check out the above article on plant nutrition and disease. Looks at Erwinia and Botrytus infections in bean plants relative to tissue calcium concentrations.

If you compare tables 1 and 2 and put in light of the antagonistic effects of potassium on calcium uptake you can see how excess K promotes loss of resistance against two disease genera that are common problems in orchids.

Thats ineresting. I always wondered why they recommended using Calcium hydroxide with urea sprays!!
The problem of getting Ca into plants is still there. Aparently it can only be taken up by (growing) root tips so that suggests spraying rootless plants with fert could be counterproductive?? ( loading up on N and K and Mg without Ca to balance them).
And feeding when the plant (roots) is inactive could throw leaf nutrient levels out of balance as well.
I think I read Ca. foliar apps. did enter the leaf somewhat but was totally imoblie so of little benefit.
So maybe just as important as reducing K is to supply Ca when the plant is receptive OR not feeding N, K and Mg when its not?
Easier said than done!!!

 

[Stone]

Afraid not. Moist stale air still has too much O2 to support obligate anaerobes.

Even the exhalation from human lungs still contains enough O2 to support aerobic bacteria. Minimal DO for supporting fish in EPA tox tests is only 4ppm. Aerobic activated sludge waste water plants typically run between 2-4 ppm of aqueous DO to minimize blower costs. From 1-2 ppm DO the falcultative anaerobes start to wake up. The obligates won't get happy until 0 mg/L. The crazy sulfur bacteria and methangenerators can't kick in until the sulfide concentrations build up to significant levels and drive ORP to crazy negative values. Sulfides can't exist in oxic environments without getting converted to sulfates.

Or...put another way....Still too much air for the little suckers.
If you fill a can with wet soybean meal and put an air-tight lid on it, well...you'll have what you're looking for..:evil:

 

[Rick]

Or...put another way....Still too much air for the little suckers.
If you fill a can with wet soybean meal and put an air-tight lid on it, well...you'll have what you're looking for..:evil:

yes:evil:

 

[keithrs]

Afraid not. Moist stale air still has too much O2 to support obligate anaerobes.

Anaerobes like Erwinia can live in o2 environments. Why can't others?

 

[Rick]

Thats ineresting. I always wondered why they recommended using Calcium hydroxide with urea sprays!!
The problem of getting Ca into plants is still there. Aparently it can only be taken up by (growing) root tips so that suggests spraying rootless plants with fert could be counterproductive?? ( loading up on N and K and Mg without Ca to balance them).
And feeding when the plant (roots) is inactive could throw leaf nutrient levels out of balance as well.
I think I read Ca. foliar apps. did enter the leaf somewhat but was totally imoblie so of little benefit.
So maybe just as important as reducing K is to supply Ca when the plant is receptive OR not feeding N, K and Mg when its not?
Easier said than done!!!

Yup the whole K lite strategy always included an increase in Ca/Mg availabilty. I agree it takes roots to do a good job with Ca uptake, but I think in several rootless cases I played with, if you plant in moss and give a dose of kelp, then even the new root nubs will help you out. If the plant went rootless because of low K, then expect the lower leaves to shed as the stem starts to push out. But because the plant will have low Ca this is the most dangerous time to expect an Erwinia outbreak too as the plant lyses off old leaves to let new growth start.

 

[Rick]

The secondary aspect of calcium hydroxide use with Urea goes with form of nitrogen.

You need higher alkalinity (from the hydroxides) to plants to utilize ammonia from urea.

 

[ChrisFL]

Bumping this thread,

Since the summer, I have been downpouring my main tank between 3 and 5 PM. I changed nothing else. Things are still soaked at night when the lights go off and the computer drops the temp to the low 70s/high 60s. My daytime temps are 86-88 on the warm side of the tank, and 79-82 on the intermediate side. Plants that have been stagnant in growth have suddenly begun to break eyes open and make new leads. I have observed zero rot and haven't lost a single plant.

 

[nikv]

I haven't read this entire thread; only the first page and the last few posts. I always thought that the "don't water late in the day" rule applied only to those plants that had crowns that would trap the water. I happen to water in the morning to mid-day simply because of my schedule. Sometimes an additional watering in the evening if it's a hot summer night.

 

[ChrisFL]

Also, I continue to use zero fertilizer. None. Nil.

 

[likespaphs]

as long as the air circulation is good and the temps are okay, i've come to the conclusion that it doesn't matter when one waters

 

[Ozpaph]

People don't catch a cold (virus) because its cold and plants don't rot just because you water late it the day. But it is true that damaged, wet tissue would be more likely to become infected than dry, healthy tissue. Its probably more about air circulation and fast growing plants being more resistant to fungal attack.

 

[ChrisFL]

Who wants to play some more in this thread?