N-fixing plants distance

Hi there,

I am starting to grow a food forest in an plot which is currently fully dominated by pine and broom (cytisus scoparius), and so are the adjacent plots. I am aware that brooms are good nitrogen fixers. I am now removing dead / diseased brooms and all of the pine trees for clearing and preparing canopy trees plantation.

My questions are as follows:
- Should i just leave brooms for nitrogen fixation? Any rules for how many / density?
- How close should they be from canopy trees?
- Can i rely on the adjacent plots' brooms for fixing nitrogen and hope that there are already there fungi will be able to transport the excess nitrogen? None of these parcels has had its soil worked in ages, so root system must be very stable. These nitrogen fixers are a maximum 30m from my future canopy trees.

Cheers,
Fernando

I have a similar situation with broom in the understory of pines and firs, forming potential ladder fuels for fire. I just cut the broom and chop it up to <12” sections and drop it on the ground. Shorter  pieces get more ground contact, stay moister and get fungally inoculated which retards their flammability, and are less likely to root. The roots will die back proportionally and improve the soil. The broom will almost definitely grow back.

Thanks Ben. Not sure if we are talking about the same species of broom; mine won't grow back. Anyway, i was thinking of nitrogen fixing and for that reason i would leave some of them planted. You chop and drop all of them, or did i understood wrong?
Cheers,
Fernando

Where I’m at the scotch broom (or Spanish, or French broom etc) are very invasive as nothing can eat it, and burning it is very toxic. They often grow back from large sections on the ground, or root suckers. Many consider them a lost cause to control without herbicides, which themselves are not very effective and will kill anything we want instead of broom as well. So I chop and drop them under my evergreens and around my hazelnuts that i planted amidst them.

Scotch Broom is a nightmare. But if you chop it small and add it to a worm bin the population and size of the worms will benefit greatly.

I am interested in the original question as well, how far does nitrogen fixation "spread"?

This is from the big black book:

Sweet man, thanks!

Thank you Ben for the clarification. Perhaps my brooms haven't regrown from the root sucker but will in the future; i only started cutting them 6 months ago.

As for the image you sent, I guess this is bad news for me: the roots of brooms don't spread so much, meaning no nitrogen fixation where I will need it (again, soil hasn't been worked, so hopefully fungi could "circulate" the nitrogen?). This brings me to another question. Next autumn I will plant my fruit canopy trees. Do they need the nitrogen to establish and grow, or only in a few years, when they are about to crop? The latter would give me chance of planning for N-fixers.

Most plants use nitrogen for growing structure and potassium for fruiting.

There is a study done about caragana shrubs and the availability of the nitrogen it releases to surrounding plants.

Under 2 meters had a negative effect, 2 - 12 meters had noticeable benefits and 12-20 meters had minor benefits.

Those figures are for established shrubs 2-3 meters tall not copiced or cut in any way.

I'm sure every type of plant and tree is different.