Re: CULT: Leaf Removal & Soft Rot

In a message dated 2/3/2003 12:18:21 PM Central Standard Time, 
jbruce1@cinci.rr.com writes:


> This is interesting, but some factor must be missing,  either
> in my data or in the university study.
> 
> The soil pH at my nursery is 5.0 down to 4.3 in spots.
> Iris flourish there, as does Erwinia. Soft rot with that distinctive smell
> at any rate. Is there another bacteria that causes soft rot that
> makes that same smell? When I say flourish, I mean grow very well,
> increase and bloom. Our pH measurements have been done twice
> by sending samples to Ohio State University Ag Extension for analysis
> as well as out own pH meter. Could the pH requirement you cite
> be dependant on soil content and type?
> 
> Always wondering about stuff.
> 

We have great commonality with the wonderin'. Too, I'm mostly parroting 
information gleaned from other sources in this instance though experience 
here tends to support the pH information. Its pretty common to find 
differences between laboratory data and the circumstances we actually 
encounter under field conditions. I usually chalk the differences up to the 
uncontrolled variables encountered in the field.

You probably already know that soil pH is a moving, ever changing target and 
is finite only at a given point in time. Each time anything is added with a 
different pH it changes the soils pH, e.g., water, fertilizer, compost. Each 
time anything is taken away it also changes, e.g., leeching, water or soil 
nutrients used by the plant or by ongoing composting of organic matter in the 
soil. Pretty much just routine chemical reactions are going on in the soil 
all the time. Ultimately, native soil will revert back to it's original 
native pH level unless some action is taken. It is also reasonable to expect 
rather wide variations in the pH levels of the individual samplings that 
constitute the final soil sample that one might collect for analysis.  
Measuring devices that indicate pH (meters and paper) do much here to 
alleviate persistent wonderin'. Interestingly, pH levels often vary 
significantly in the immediate area of live root mass filaments from that of 
the surrounding native soil. Given the opening of this paragraph this is not 
unexpected.

Cooley's I believe suggests a neutral to slightly higher pH. Sutton has 
stated they are growing in about 7.1. Other posters to this list have grown 
in higher pH levels. I suspect many, like yourself are growing in much lower 
pH levels. Here, I've made some effort (though far from controlled research) 
to grow/evaluate growth rates at different pH levels and observe propensity 
for rot to occur in those same beds. Maximum (18x) increase of any plant here 
was achieved by Keppel's Local Color. It was grown in a soil pH that varied 
between 7.8 and 8.1. I have however, observed rot in this particular bed. I 
also let rot run its course as it was encountered. I have yet to totally lose 
any of the 30 different plants growing in it. An adjacent bed containing a 
different 25 plants growing in pH levels between 6.5 and 7.2 has had some 
total losses. Higher pH beds (pH 10 and up) have never been observed as 
having any rot. I would like to say this was planned. It wasn't. Just 
observed. The high pH levels resulted from using burn piles to raise soil 
nutrient levels with higher pH being the result.

I do not know if another bacteria produces the characteristic smell of 
Erwinia c. I do not personally think God is mean so maybe not. But, He does 
have a sense of humor and there are other Erwinia stains. Erwinia c. is 
present in soils world wide.

I would think it both possible and probable that soil content and type can be 
contributing factors-considering that we are measuring average pH not the pH 
of individual soil particles. Indeed, we might even view each individual soil 
particle as its own little micro world either neutral, hostile of comforting 
to Erwinia c. I have mentally speculated that nitrogen application/soft rot 
correlation reported by iris people are actually nitrogen application/pH 
micro world changes/soft rot correlation.

Those missing factors? Maybe moisture levels, temperature and/or ultraviolet 
light saturation?

Smiles and wonderin' (mental speculation to those without an interpreter),
Bill Burleson 7a/b
Old South Iris Society

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