AusBonsai

Hi bonsai heads.

I have been getting more interested in growing casurina and after some research have learnt that they are nitrogen fixing plants . I am assuming this means they don't need nitrogen and make it themselves with help from bacteria in the soil. Can anyone shed more light on the subject please.? Is it ok to feed them nitrogen and what ferts are good for them.

I have a couple of air layers and was wondering will they be ok being bare rooted from the spag moss and roots sorted out. After a year ?. If I chop the moss and add diatomite it should bare root easily ?

Treat as normal but remember that hey can draw nitrogen from the air in some way I fear not to be specific

Hi Paul,

They contain bacteria in nodules on their roots that can "fix" nitrogen. The bacteria take nitrogen gas from the air (the most abundant gas that makes up the "air" around us) and bind it together in a form that the plants can use. This trait is common amongst Casuarina and Allocasuarina. It is most prominent in the pea family (Fabaceae) and demonstrated by Acacia, Wisteria, Bauhinia and many other plants used as bonsai. As far as I can tell, it doesn't change their culture much. You still need to fertilise so the plant has access to the other 18 solid (hydrogen, oxygen and carbon come from air/water) nutrients they need.

Joel

Thanks guys . And what about bare rooting a air layer from moss to arrange roots. Will they cope ok with that treatment?

Cas airlayer readily, maybe transfer some soil from a healthy specimen to make sure the bacteria come across.

Casuarina family are nitrogen fixers but use a different technique to the legumes which have bacteria to change nitrogen. Casuarina have fungi in the roots that does the same job (possibly similar arrangement to pines?). Frankia species are some that have been identified as nitrogen fixers associated with casuarina but more research is showing there are others as well. Research is still happening to identify the best strains of Frankia and others that appear to be associated with nitrogen fixing in casuarinas but it is clear that some species of fungi are more efficient than others (just as some strains of bacteria are better at nitrogen fixing in legumes).

Just like the legumes, casuarina do not NEED their symbiotes to survive. They are only really useful where soil nitrogen is low so a well fertilised casuarina should not need the fungi to grow well. As fungi spores float around in the air it is likely that all casuarinas will end up with some in any case.

Fixing nitrogen is a very energy intensive job. The N2 molecule of atmospheric nitrogen is very stable and needs lots of energy to split it so the nitrogen atoms can combine with other elements and be available for the bacteria, fungi and plants. If there is plenty of plant ready nitrogen compounds available the fungi and bacteria (and plants) don't bother to waste the energy, they just use the available soil nitrogen. This means that if you fertilise well the nitrogen fixing ability of the fungi/bacteria is redundant and only really kicks in when soil nitrogen starts to get scarce.

The other thing to note about nitrogen fixing plants is that organisms are not altruistic. Legumes do not fix nitrogen so they can donate it to other plants. In the wild it is every organism for itself in the struggle to survive. The bacteria in the roots convert nitrogen gas and then 'trade' it with the plant in return for other nutrients and energy the plant produces in its leaves. The legumes hoard the precious nitrogen for their own use. It only becomes available to other plants when the legume (or parts of it) die and rot away (or are eaten and procesed by animals) to release the nitrogen compounds stored in the tissues. Then its every plant for themselves again to grab what they can.
This means that growing legumes with your other plants will not make the other plants grow better. The legumes compete just as well for soil nitrogen as weeds do. Legume nitrogen is only available when the legume dies and rots away.

All fascinating stuff but always just a little more involved than most realise.

That was a good read shibui, helpful and informing. Thanks

shibui wrote:Casuarina family are nitrogen fixers but use a different technique to the legumes which have bacteria to change nitrogen. Casuarina have fungi in the roots that does the same job (possibly similar arrangement to pines?). Frankia species are some that have been identified as nitrogen fixers associated with casuarina but more research is showing there are others as well. Research is still happening to identify the best strains of Frankia and others that appear to be associated with nitrogen fixing in casuarinas but it is clear that some species of fungi are more efficient than others (just as some strains of bacteria are better at nitrogen fixing in legumes).

Just like the legumes, casuarina do not NEED their symbiotes to survive. They are only really useful where soil nitrogen is low so a well fertilised casuarina should not need the fungi to grow well. As fungi spores float around in the air it is likely that all casuarinas will end up with some in any case.

Fixing nitrogen is a very energy intensive job. The N2 molecule of atmospheric nitrogen is very stable and needs lots of energy to split it so the nitrogen atoms can combine with other elements and be available for the bacteria, fungi and plants. If there is plenty of plant ready nitrogen compounds available the fungi and bacteria (and plants) don't bother to waste the energy, they just use the available soil nitrogen. This means that if you fertilise well the nitrogen fixing ability of the fungi/bacteria is redundant and only really kicks in when soil nitrogen starts to get scarce.

The other thing to note about nitrogen fixing plants is that organisms are not altruistic. Legumes do not fix nitrogen so they can donate it to other plants. In the wild it is every organism for itself in the struggle to survive. The bacteria in the roots convert nitrogen gas and then 'trade' it with the plant in return for other nutrients and energy the plant produces in its leaves. The legumes hoard the precious nitrogen for their own use. It only becomes available to other plants when the legume (or parts of it) die and rot away (or are eaten and procesed by animals) to release the nitrogen compounds stored in the tissues. Then its every plant for themselves again to grab what they can.
This means that growing legumes with your other plants will not make the other plants grow better. The legumes compete just as well for soil nitrogen as weeds do. Legume nitrogen is only available when the legume dies and rots away.

All fascinating stuff but always just a little more involved than most realise.

Thank you very much for the correction shibui! At TAFE I was told it was the same process as legumes, so assumed that was true. I imagine there would be interest in genetically modifying Frankia species to infect crop species along with other mychorizas. Fascinating indeed!

Joel

I did hear of a bacterial?/fungal? treatment for wheat seed that was supposed to allow the plants to extract more (phosphate I think) from the soil and therefore grow bigger and better with less added fertiliser but did not take enough notice at the time because I don't need to know! but I assume that someone is just a bit ahead of you there Joel.

shibui wrote:I did hear of a bacterial?/fungal? treatment for wheat seed that was supposed to allow the plants to extract more (phosphate I think) from the soil and therefore grow bigger and better with less added fertiliser but did not take enough notice at the time because I don't need to know! but I assume that someone is just a bit ahead of you there Joel.

Argh It's all been done before. Oh well. I'll have to get rich another way