Phosphorus questions
iris@hort.net
  • Subject: Phosphorus questions
  • From: S*@aol.com
  • Date: Sat, 7 Apr 2012 18:25:51 -0400 (EDT)
Hi All:
 
I am writing a newsletter for the  club.  I have been reading about 
superphosphates on the web and am  confused.
 
1.  Is treble superphosphate  harmful to earthworms?
 
2.  Some websites suggest  that treble superphosphate has to be carefully 
measured to avoid burning the  plants.   Though other websites  state that 
salt index is the usual measure of a fertilizer's tendency to burn  roots. 
According to these sources, triple superphosphate has an exceptionally  low 
salt index and is very unlikely to harm roots.   Who do you believe?  
 
3.  Rock phosphate is very insoluble.    It will stay where you put it 
unless the soil washes away.   However, Superphosphate  is rock phosphate that 
has been treated with acid to make it soluble.  Does  that mean it can be 
washed away from the point of application?  How long  before it gets converted 
to the regular rock phosphate?  Or does it too  combine quickly with just 
about any available mineral in the soil (i.e. iron,  zinc, manganese)?  
 
4.   Does anyone know what type of phosphate BR-61 contains?   It's  the 
club's favorite and high in the middle number.  We buy it in bulk and  parse 
it out to members.  Instead of being $9 a lb it comes out to $3 a  lb.  
However, I have no container to  read.
 
Thanks  a bunch

Scarlett

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