N fixer - a tree vs. shrub, flowers, clover (need advice)

I just planted a 30 tree orchard and used  Stefan Sobkowiak's approach of a nitrogen fixing tree between two fruit trees.......
Unfortunately  ALL of the N fixing trees died. Dead as a door nail.   I used Alder trees.  

I'm rethinking my approach now.   So do I:
1)  replace the trees ?  
2) put in a shrub/bush  ?  
3) put in a few Blue False Indigo's ?  
4)  get clover going on either side ?  (which i was going to do anyway)
5) combination of the above.

Does StefanS use trees because they supply way more nitrogen than a shrub/bush ?   Or is it for maintainability ?

You thoughts ?

Thanks in advance.

-mark

The big question is what all do you want the N fixer(s) to do for you. Just fix nitrogen that is instantly available in the soil surrounding the roots? Fix Nitrogen long term so that only when the plant dies the nitrogen becomes free? Have both short term and long term availability of nitrogen?
Then there is the issue of the horticultural fact that all plants fix most of the nitrogen they use from the air they breathe, not take it up from the soil, except during their dormant period.
Vegetable plants will take up nitrogen from both the air and the soil since they are producing the part of themselves that we will harvest and eat.

If you need the extra shade, then tree and bush/shrub type N fixers would be the best choice.
If you are using these for short term, cover crops to either chop and drop or turn under for organic matter in the soil, then clovers and other lower growing, annual type plants would be the best choice.
If you need to both improve soil organic matter and provide extra shade as well as providing some extra N for the bacteria and fungi living in your soil, then a combination would be the best choice.

To make the best decision for your plot of land, first you have to decide how you are going to use each portion and that will help you determine which type or types of N fixers to utilize.
Example, pastures benefit best from annual types of N fixers since most of these are also good sources of fodder for the grazing animals, you don't have to worry about performing a chop and drop or turning under at the end of their life cycle.
If you are looking to increase pollinator attractor plants, then all the N fixers that flower and staggering them so every space always has something flowering would be the way to go.

Generally trees last the longest, but if they aren't evergreen species then when these trees go dormant, they are going to be utilizing a lot of that N they stored around their roots for their own needs.

Redhawk

I'm personally going with your 5) in my food forest area.  I'm using black and honey locust, autumn olive, alders, false indigo, and dutch white clover.  My thinking is simply that I'll cover all my bases.  If the trees do well, great.  If the indigo does, super.  If clover thrives, I'll mow it and leave it in place.  The more diversity, the more resilience in my mind.  If any of those plants don't do well, hopefully something else does, and I'll keep adding different ones as I find them.  If the trees get too big and cause more shade than I like, I'll coppice them.  If they die, they served their purpose.  I'm getting my nitrogen fixers from seeds, cuttings, transplants from other areas of my land, so they are all basically free. My investment is just my time, and it is something I enjoy so that works out well too.

So you are saying that the N isn't available until after the N fixing plant dies.....is that correct ?   Hmmm.   I thought that both plants had access to the N ---- the N fixer itself and the non-N fixing fruit tree.

If I understand this correctly,  then all that N that the Locust trees fix will not be available to the fruit trees until after you cut it down.   That's a long time.  

Sorry, but now I have more questions.

Are clovers able to supply nitrogen to the soil b/c the individual plants don't live that long ?
Do N producing flowers like Blue False Indigo supply nitrogen even if they come back in the spring ?

The goal is to supply N to the fruit trees for growing purposes.

Thanks.  This is very valuable info.  I guess I should consider green beans.

Hi Mark,

Where are you located regionally? Annual rainfall and altitude may also play a factor if its outside of the regional norm for your area. Those factors will definitely help in determining what species can survive or thrive in your area.

Mark Sullivan wrote:So you are saying that the N isn't available until after the N fixing plant dies.....is that correct ?   Hmmm.   I thought that both plants had access to the N ---- the N fixer itself and the non-N fixing fruit tree.

If I understand this correctly,  then all that N that the Locust trees fix will not be available to the fruit trees until after you cut it down.   That's a long time.  

Sorry, but now I have more questions.

Are clovers able to supply nitrogen to the soil b/c the individual plants don't live that long ?
Do N producing flowers like Blue False Indigo supply nitrogen even if they come back in the spring ?

The goal is to supply N to the fruit trees for growing purposes.

Thanks.  This is very valuable info.  I guess I should consider green beans.

I use beans as well, but my understanding is that you have to cut the plants before they make beans to use them for nitrogen.  The good news is, if you plant 20 extra bean plants and let them go to seed, you'll have hundreds to plant the next year.

Mark Sullivan wrote:So you are saying that the N isn't available until after the N fixing plant dies.....is that correct ?   Hmmm.   I thought that both plants had access to the N ---- the N fixer itself and the non-N fixing fruit tree.

If I understand this correctly,  then all that N that the Locust trees fix will not be available to the fruit trees until after you cut it down.   That's a long time.  

Sorry, but now I have more questions.

Are clovers able to supply nitrogen to the soil b/c the individual plants don't live that long ?
Do N producing flowers like Blue False Indigo supply nitrogen even if they come back in the spring ?

The goal is to supply N to the fruit trees for growing purposes.

Thanks.  This is very valuable info.  I guess I should consider green beans.

Things like Honey Locust will share N with those plant roots that are in close proximity, however for most plants as little as 10 percent N in the soil is plenty of N in the soil. (Gabe Brown has for the most part proven that even heavy N feeders such as Maize (corn) will do quite well in soil that only contains 10% free nitrogen).
Nitrogen, to be usable by plants needs to be in the form of ammoniates, those are the molecules that plants bring in through the roots.
Most of the Nitrogen comes in as NO2 from the air, entering through the stoma during the process of respiration during the daytime, at night the roots bring up the ammonia compounds and the mitochondria break those molecule bonds, releasing energy and Nitrogen atoms which the plant cells then utilize.

Nodule forming plants such as clover keep the nitrogen fixing bacteria inside the nodules and that is also where the fixed nitrogen resides until the plant excretes an exudate call for that nitrogen.
Since this type of plant stores the fixed nitrogen within its root cellular structure, it is not readily available for other plants to use.
When there are mycorrhizae present (both exo and endo types) other plants that send out exudates calling for nitrogen might have their exudate call travel, via the mycorrhizae, into the root nodules thus allowing a release of N to the exterior of the root system.
This is currently under study so we might better understand the exact workings of the fungal network within an area of root systems and different types of plants. The current theory is that the nodules don't share, but there is beginning to be some evidence showing that what was previously thought is not quite correct.

The more we delve into the microscopic workings of the plant world, the more complex, previously thought of as simple, systems become.
Increasing available nitrogen for plants to use is not as simple as previously thought, it is turning out that many of the plants don't need to die, they need mycorrhizae present around and inside their root systems to provide nitrogen which is provided by the rhizobacters present in the nodules that form on the roots.


My personal view point about N fixers is that we need to consider using a very diverse set of plants to achieve the goal of Nitrogen enrichment, should we have decided we need to provide such enrichment to our soil organisms.

Redhawk