Bean roots, do we or don't we

[lottieguy]

Hi Ya, Having just read the October issue I am wondering who is right. On page 70 it says in the organic myths that leaving bean roots in the soil does not, as most including myself believed for years, that nitrogen is not fixed in the soil, however on page 101 October jobs, it says to leave the bean roots in the soil to add nitrogen? I am curious now who is right? Does any one on here leave the roots in? I wonder what other curious things we do that are not right. Still each too their own. It did amuse me.

[veggiechicken]

I've no idea what's right or wrong (do they add nitrogen whilst growing that can be used by other plants nearby at the time?).
I leave them in the ground as runner beans have regrown the following year. That's enough reason for me to leave them in place.

[mcdood]

The latest perceived wisdom appears to be that they fix nitrogen while growing but not when dead so I take the roots out now.

[Thelma Sanders]

I've been saying for a few years now, that research showed that by the time they've set seed and been harvested, there is no nitrogen in the roots, so unless you are actually digging in the tops as well, you're not adding anything to the soil other than the organic matter. Some links in here …

https://www.gardenmyths.com/legumes-add-nitrogen-soil/

[Jay-ell]

Yea, the myth was that the extra nitrogen locked in by the symbiotic bacteria would be held in the nodules on the roots and released when the roots decompose whilst the truth is the bean plants use up all that extra nitrogen together with any that it scavenges to produce the leaves and beans.
Here's my video gripe about it https://youtu.be/OKwYZlY9BTM

Having said this the roots will still contain some nitrogen - in a similar way to any other plants rootswill contain some nitrogen - as nitrogen is a component in amino acids which are the building blocks to proteins. Proteins are the way living organisms actually do things so occur throughout the plant in different amounts (e.g chlorophyll is a protein which absorbs red & blue light and then uses the energy to convert co2 into sugars).

Roots will also contain phosphorus which is used in a number of plant functions including root development and also some potassium which is used all over the place in a number of different roles including photosynthesis, celular development, flower/fruit development.

So basically any plant roots will contain varying amounts of the three main nutrients and also contain organic matter which will rot down and improve soil structure so I'd say leave the roots of anything that dies off in the ground to improve the soil including beans.

[Gillykat]

The first year I had my allotment I had French green beans and peas and I really worried about not managing to leave every single bit of root behind at the ed of the season! I laugh about it now but at the time (it being my very first time growing veg in my life!) I was panicking about losing soil fertility.

Now, of course, I now it's not gospel so I just pull the whole lot up and they go on the compost heap

[ameno]

They contain barely any. It's used by the plant, after all, so most of it goes into the leaves and the seeds.
Legumes only really increase soil nitrogen when grown as a green manure, as then the whole plant, and thus all of the nitrogen they have captured, is being dug back in.

[Penellype]

I put mine on the compost heap. If they contain nitrogen then it will end up in the compost.

[Bren In Pots]

A few get dug up up overwinter in the GH the rest are left until I add Dalek compost to the trench ready to grow beans again.

[jackarmy]

I have only seen notable nodules on broad bean roots, runners and frenchies have virtually none that i have seen.
The theory that they use the nitrogen they make i believe, but i also believe that Broad Beans at least leave some behind via the root.

[ameno]

I have only seen notable nodules on broad bean roots, runners and frenchies have virtually none that i have seen.
The theory that they use the nitrogen they make i believe, but i also believe that Broad Beans at least leave some behind via the root.

Nitrogen isn't really "stored" by plants in the same way carbohydrates are. It's used in the plants primarily as protein, so the bits which have the most protein have the most nitrogen.
The seeds (i.e. beans) have the most, then the leaves, then the stems, then last of all the roots, although all parts have at least a little.

Digging in the roots won't hurt, of course, but don't expect it to increase the soil nitrogen by any measurable amount.

The root nodules, by the way, are just where the nitrogen-fixing bacteria live. They don't actually store any nitrogen. The nitrogen compounds the bacteria make are taken up by the roots and transported around the plant pretty much straight away.

[jackarmy]

I was just stating my observations not my scientific research