North American Fruit Explorers mailing list at ibiblio

["Joe Hecksel" <jhecksel@voyager.net>]

Hi Andrew:

> i am in the planning and saving money stages of creating a farm in 
northern wisconsin, 
> my first questions to this list are concerning nitrogen fixing 
trees/plants in relation to fruit and nut orchards... but my research 
has shown that too much nitrogen is very bad for fruit and nut 
production.  

<Joe writes>
IMHO, you will get more N coming in on the mulch than from the nitrogen 
fixing plants.  The top-end for a 100%, well-watered clover sward that 
is in full sun is about 250 lb N/acre/year (250 kg/ha/yr).  Most 
commercial orchards apply +100 lb N/acre/year.  Fiddling around with 
the numbers, you need at least 30% of your intercepted sun hitting N 
fixing plants.  That is not 30% of the trees, that is 30% of the area.  
A very important piece of the fine-print is "well watered".    
>  
> i was considering Eleagnus sp. in between rows of fruit trees with a 
bunch of comfrey or other suitable mulch plant nearby to pick up 
excessive nitrogen while still being able to supply some to the fruit 
adn nut trees.  I also considered planting lupines under teh trees and, 
of course, clover and grass pathways.  
>  
<Joe writes>
Some people will get on you for Eleangnus because it is often 
considered an invasive, non-native.  I am neutral on the issue but the 
people you want for customers might object.  If you go with Eleangnus 
you will need to keep whacking them down so they do not shade fruit 
producing plants.  Some also sucker.  Another issue is that most of the 
N will leave the orchard when the wind blows the orchard floor clean in 
the fall.  Leaf drop is the primary N transport mechanism.

Again, IMHO, I think the hot ticket is to plant the N fixing plants and 
get what you can for free.  Use the composition and amount of mulch to 
modulate N amount.  

Modulation of N is a little tricky with mulch because you have fewer 
decision points to make adjustments.  Again, let me stress that you do 
not want water to be a limiting factor in growth because that will fake 
you out into adding far more N than is desirable.  It is easy to become 
frustrated because of slow response and overshoot your objective.

A common set of objectives in Southern Michigan is to have 2' (600mm) 
of shoot extension while the canopy is filling and 1' (300mm) of shoot 
extension during the bearing years.  Objectives vary by 
species/cultivar, growing season and severity of winter and fireblight 
pressure.


-- 
Joe Hecksel
Personal Webpage http://my.voyager.net/~jhecksel