Jerry Baker in all his infinite gardening wisdom *cynical laughter*
seemed like common sense to me but if it would help...
the occurrence and effects of oxygen depletion has been widely studied in flooded soils
it lowers redox potential, changes the composition of the soil's microbial community, affects the form and mobility of N, Fe and P, increases methane levels, co2 levels, etc etc
(Patrick, 1977, Hook 1984, Faulkner et. al., 1989, Drew 1991, Crawford 1992, etc etc.)
I got 19,000 hits when I used google scholar.
and the fact that water draining through the pot will be replaced with fresh air is simple physics..
but as EST pointed out... I could ask for evidence that black is black in such a way that you couldn't provide it, so what does it matter
Instead of debating why we may not agree, lets just reply to every thread with "prove it" from now on.
I have to ask Av8tor. Did you even look at the question I asked?
I had also wondered if you had read my original response, the original poster asked for comments about the claims that flushing the pots increased oxygen levels.
My entire response was in reply to that.
I even quoted the original poster...
then you came back and asked if that was my opinion or if i had done trials...
and I said I felt it was common sense, which i do... and I stopped posting... so yeah, i think so
So if I wanted to challenge the physics I would edit all reference to the physics from the quote?
if you feel oxygen is not needed in the root zone then please post why you think it doesn't matter, ill read it and consider it
maybe I'm wrong.... but to me that seems like common sense too
I can't believe this debate() has gone on for so long. Amusing, to say the least.
There are plenty of studies on the formation of aerenchyma in the roots of plants in response to flooding. Many plants will form the internal spaces in the stems, rhizomes and roots to increase oxygen transport to the roots when placed into anaerobic conditions. Some will just grow shallower roots as the oxygen content is higher towards the surface.Most soils are aerobic. This is important because plant roots respire (that is, they consume oxygen and carbohydrates while releasing carbon dioxide) and there must be sufficient air—especially oxygen—in the soil to support most forms of soil life. Air normally moves through interconnected pores by forces such as changes in atmospheric pressure, the flushing action of rainwater, and by simple diffusion.
In addition to plant roots, most forms of soil microorganisms need oxygen to survive. This is true of the more well-known soil animals as well, such as ants, earthworms and moles. But soils can often become saturated with water due to rainfall and flooding. Gas diffusion in soil slows (some 10,000 times slower) when soil becomes saturated with water because there are no open passageways for air to travel. When oxygen levels become limited, intense competition arises between soil life forms for the remaining oxygen. When this anaerobic environment continues for long periods during the growing season, quite different biological and chemical reactions begin to dominate, compared with aerobic soils. In soils where saturation with water is prolonged and is repeated for many years, unique soil properties usually develop that can be recognized in the field. Soils with these unique properties are called hydric soils, and although they may occupy a relatively small portion of the landscape, they maintain important functions in the environment.
The plants found in hydric soils often have aerenchyma, internal spaces in stems and rhizomes, that allow atmospheric oxygen to be transported to the rooting zone. Hence, many wetlands are dominated by plants with aerenchyma; common examples include cattails, sedges and water-lillies.
Diffusion is a rather slow process - the amount of time it takes for a substance to diffuse is proportional to the square of the distance traveled. If it takes 1 second for something to diffuse 100 microns in water it will take 100 seconds for 1mm and 10,000 seconds (2.78 hours) to diffuse 1cm. That's why fish flow water over their gills - to clear away CO2 and other waste products and get more oxygen. Water flowing over roots would perform a similar process.
The Anatomical Characteristics of Roots and Plant Response to Soil - S.H.F.W. Justin and W. Armstrong
Lysigenous aerenchyma formation involves non-apoptotic programmed cell death in rice (Oryza sativa L.) roots - Rohit Joshi and Pramod Kumar
Oxygen transport in soil and the vertical distribution of roots - F. J. Cook, J. H. Knight, F. M. Kelliher
If you want to question the relevance of these studies I'll just say they were conducted in the UK, US and Australia on a number of Wetland, intermediate and non-wetland species.
Consider this also
Influence of root zone oxygen stress on potassium and ammonium absorption by Myrobalan plum rootstock - C. J. Rosen, R. M. Carlson
Growth chamber experiments were conducted with ‘French’ prune (Prunus domestica L.) scions grafted on Myrobalan 29C (P. cerasifera Ehrh.) rootstocks grown in nutrient solution to characterize K and NH4 uptake before, during, and after anaerobiosis. Conditions of oxygen stress were imposed by removing the source of aeration and bubbling solutions with nitrogen gas.
At solution oxygen concentrations less than 1%, K leaked from plant roots. After 18 h of anaerobic conditions, aeration was restored and K depletion from solution occurred within 2 h. Uptake of K the following day was similar to that before oxygen stress was imposed.
Under similar conditions with solution oxygen concentrations less than 1%, both K and NH4 uptake were inhibited. Potassium leakage from roots was significantly greater than that of NH4. The presence of NH4 had no significant effect on K leakage from roots. Signs of wilting during oxygen stress appeared first on those trees that received NH4. Potassium uptake by rootstocks in the presence of NH4 was inhibited prior to and following anaerobiosis. However, the extent of NH4-induced inhibition of K uptake before anaerobiosis was similar to the K uptake inhibition after anaerobiosis.
Grand Hotel... always the same. People come, people go. Nothing ever happens.
I never said that getting air into the root zone wasn't a good thing. Flushing isn't the only way to get it there. Top watering will introduce air, so will tray watering when the pot is lifted out, the science will demonstrate that. Not everyone thinks flushing is the way to do it so do they not have common sense? There are other ways of introducing air and there are many different growing conditions to take into account
If I may point you back to my question there was an option to say it was your opinion that flooding may be beneficial rather than the definite will be, as implied by your "common sense" reply. You chose not to go that route. It is my opinion that the former is a more honest and correct response.
I don't think anyone's talked about "flooding", just "flushing"...but I may have missed something.
Last edited by tje25; 01-25-2015 at 08:02 AM.
My Nepenthes thread! http://www.terraforums.com/forums/sh...avis-Nepenthes
My Grow List! http://www.terraforums.com/forums/sh...d.php?t=129188