Wheat under Robinia pseudoacacia, unexpected results on experiment

Hi there,

I wanted to submit to this forum the unexpected results we got with a friend of mine in France, on experimenting wheat planting in regenerating forest.

Context :

- Both of us have some clues in agroecology, permaculture, and farming, and I have a degree in biology-ecology and I give permaculture courses in France (just to say we do know pretty much how soil ecology usually works..

- We planted in autumn a mix of three wheat of old vigorous varieties (very different ones, the idea was to plant the mix and collect the seeds keeping a record of the different varieties but with a little cross pollination) and added some companion species in the mix.

- the soil all around is mostly high-humus rich forest soil (200m of a big river), a super soil but anciently planted of vines (which of course destroyed the soil for a long time), but then came Robinia p. and other invasive pioneers like Ghetto Palm (Ailanthus altissima)
and now we have many Fraxinus sprouting indicating the soil is now much better, and it structure seems nice. the vegetation is dense where light reaches the soil.

- The parcel itself, on a hundred square meters of this regenrating forest, we have ten Robinia 15 to 25 cm diameter that were left untouched (only a few were cut down), not much vegetation there (we thought because of the light barrier on the side, coming from big edge trees)

- so to improve and grant the light source for our wheat, the main source of light (coming from a open-field at 10 meters) was largely improved by cutting a lot of tree branches on that forest edge, clear difference now. (most of the cuttings went for his goats

- while planting, we just did a light, mostly superficial earth work to help germination and hide the seeds for ants (south of France, department 07, we have foragers ants, super girls, whenever you put seeds on bare soil, they collect almost every single seed in hours

- added a little mulch of a few centimeters with rotting materials on superficial forest around.


Results :

- The wheat germinate ( fewer than expected for seeds of the year before that did pretty well)
- the companion species also germinate (also fewer than expected)

- the plants are unexpectedly weak , 35 cm high, but with a few stems, light green ...


My reading is that the stable humus of the forest is not active enough to release its nitrogen, the absence of light the year before did not permit herbaceous level growth, conditioning the nitrogen main available source for this year. Or could it be the Robinia root network that is taking most of the water falling there ? shall we have used pigs to work more the earth before planting ? ... could be ... or an old chemical there, inhibiting wheat grow ... I don't think so : 300 meters from there is a nice open field full of happy grasses. We thought the acacia leaves would have given enough food for the year on that soil but seems like we shall have done another herbaceous leguminous planting a few month before ...

Any other ideas or readings are very welcome !!!

Have a nice day !

S.J.

I think that water/nutrient might be the issue, I have seen pictures of alley cropped corn where you could see smaller and smaller plants as you got closer to the trees. One way to prevent this problem is through root pruning (using a subsoiler). I have heard from Mark Shepard last summer that his experience with black locust (Robinia pseudoacacia) was that it improved the growth of grass, so it should improve the growth of your wheat (in theory).

I wonder if there are not other factors at play here.

As a note on the ability of black locust to fix nitrogen, here is a picture of a black locust seedling I transplanted last year. You can see the nitrogen fixing nodules!

Sounds like you planted grass that wants a bacterial dominated soil ecosystem in a forest area with a fungally dominated soil ecosystem.

I would suggest getting some soil biology testing done to determine that aspect of your soil.

Was there any particular reason that you were doing this experiment?

Thank you Peter and Adrien !

Looks like we do have a fungi and I guess mycorrhizal dominated soil for sure, even if black locust have a lot of bacterial nodules association, (but these are located in the nodules mostly, right!?) ... observation is the key,... and yes this is part of the problem.

Root pruning could have been a solution if done well before and if we don't care keeping the trees in good health ... which is mostly the case here ... but we had no subsoiler (anyway I keep this good idea, because my friend has a nice and friendly pony). Another "sort of solution" would have been giving the choppings to the soil, and not to the goats for once, ... but we could also have used any of the non-edible-plant-for-goats growing nearby in good quantities, or using a forest green manure (do you know any good ones?, I will look for wild herbaceous nitrogen-fixing plant under the canopy to collect seeds for the next time;-)

I'm somewhat sure that choppings or green manure would have prepared for my grass (wheat) much better, helping bacterial and soil activity in there !

About the question of particular reasons of this experiment, well we are experimenting and confronting our ideas to the reality of a small family farm more and more engaged in permaculture, having a lot of black locust forest at about 800 meters from house, goats, chickens, pony, ducks, and a forest garden 200m from house and a nice food production in front of the house, many palm trees and food trees, and we are having fun with aaaa lot of experiences !! ;-) ... so the idea there was to test a low-maintenance wheat production in chopped canopy and edge of black locust dominated zone.

Best regards,

S. J.

If it is a question of fungal/bacterial dominance then perhaps consider alternative crops to wheat in future - play to the strengths of your environment rather than fight what is there.

Stephane Jansegers wrote:
Root pruning could have been a solution if done well before and if we don't care keeping the trees in good health ... which is mostly the case here

If root pruning is done from when the trees are young, it should not have ill effect on their health. It might be too late for your trees though.

Vocabulary question, do you call those trees Robinier faux-acacia in France? This is what we call them in French Canada (although they seem not to be very common in Québec).

You are right Michael ! Let's not struggle for growing things where they seem not to like growing. In our case, considering phytosociology and observation, and the logic of soil regenaration, I'm convinced that trees and grass there should do very well and that something is (or was) missing in my understanding of the global picture. We are conducing a lot of experiments and I don't have the impression to get in any fight at all bad results are just happy occasions of more understandings !!

Adrien, we do call those trees Robinier faux-acacia in France, and most people just talk about "acacia" for black locust (for example : "le miel d'acacia" is used for black locust honey) ... because there aren't thousands of species like in tropical latitudes !

Thanks guys.