North American Fruit Explorers mailing list at ibiblio

[Alan Haigh <alandhaigh@gmail.com>]

My limited understanding (I'm not in the business of rasing annual crops) is that access to soluble P is particularly crucial in the early season establishment of of annuals.  Once mychorizal relationships are established there is often a less of a pressing need for supplementary soluble P.  I think it was Elliot Coleman who stressed this in his first book, "The New Organic Grower"- it was years ago I read it.  

 

Have any of you diagnosed P deficiency in your fruit trees?  Cornell routinely advises adding phosphorous when preparing an orchard site- even when the soil contains reasonable amounts.  I wonder if concerns about P deficiencies in fruit production aren't overblown. 

 

I have heard of Hudson Valley growers who have taken heavy crops of apples out of soils for 40 years without any supplemental P.  I know that in ornamental arboriculture, phosphorous is considered rarely needed, at least by my main guru in the field, Richard Harris.  He supports this position with considerable research on tree responses to fertilzation.  Usually trees only respond to N- even when their leaves are carted off every year.