All the plants were infected, you can see clusters of nodules on a lot of the roots of the plants that I just removed today. Many of the nodules remained in the soil when I pulled the plants out.
I have to say that I was really pleased to see all those nodules. Happy to see infected plant roots?!! Absolutely, I intentionally infected the plants myself. It's a bacteria that has a symbiotic relationship with its host plant. The bacteria invades the plant roots and creates those nodules. The rhizobium within the nodules fix nitrogen from the atmosphere into a form that can be used by the plant. The plant in return supplies the bacteria with food and oxygen. The bacteria usually fix more nitrogen than the host plant can use and the excess remains in the soil and can be used by plants that are grown in that area after the host plant dies or is removed.
Most legumes have symbiotic relationships with nitrogen fixing rhizobium. Each type of legume hosts a different strain of the bacteria, so fava beans (Vicia faba) host a different strain than do peas (Pisum sativum), and soybeans (Glycine max) and green beans (Phaseolus vulgaris) each host their own strain as well. Other familiar legumes that host rhizobium are clover, alfalfa, lupines, and peanuts. I've even pulled up weedy burr clover that has had root nodules. The rhizobium dwell in the soil and can detect and infect their appropriate host when it starts to grow. If you inoculated your beans or peas when they were sown in a particular location in the past than you shouldn't have to inoculate them again when you plant them in the same area, the bacteria should still be present in the soil. I've used an inoculant each time I've sown legumes in my garden since I've been rotating them around the garden and I haven't planted each type in each bed yet. Once I've rotated each type of legume through each bed then I shouldn't have to inoculate my seeds anymore, but it wouldn't hurt if I did.
If you've not been happy with the performance of the legumes that you've been growing in your garden you might be able to improve the productivity of your next crop by trying an inoculant. Inoculants can be purchased in a powdered form from various seed companies. The packaged inoculant is a living thing so it is highly perishable. Buy only what you need for one season and be sure to buy the correct strain for the legume that you are sowing. Most of the products that I've seen are a mix of strains to inoculate beans, peas, and favas, but soy rhizobium are generally not included in the mixes, you probably need to buy that separately.
That's really cool. I've never seen anything like it. I'm sure the next crops you plant in that spot will benefit greatly.
ReplyDeleteBeautiful! Legumes certainly are the heroes of our gardens. I never pull the roots out, but just whack the main stems down to just below the surface of the soil and leave the roots to fertilize whatever I plant there next. Occasionally, favas try to grow back for me, but the pole beans, bush beans, and peas don't some as desirous to grow back. Favas seem to be the best nitrogen fixers I grow.
ReplyDeleteA fascinating post which I'll come back to again. I knew there was an important connection between beans and nitrogen, but didn't understand the science. Thanks.
ReplyDeleteI like your new minimalist design for the blog!
You had me going there at the first. I was thinking "but you want those nitrogen fixing nodules on the roots"!?
ReplyDeleteI inocculate if I am planting legumes where none have been before. Always thrilled to see the pinkish/white nodules on the roots. Like Christina, I leave my pea roots in the ground and just cut off the vines. They quickly decompose and ensure that the next crop in the bed will be superior.
I always thought that by leaving peas roots in the soil, you automatically add nitrogen. I never thought that I need any further activity to that.
ReplyDeleteThanks for this post, I have learned something new.
Great photos of the bacteria! I've seen it before but never taken a photo. And it reminds me to inoculate my pole bean seed when I plant it. Like you, I'm still working my legumes through a rotation.
ReplyDeleteThe rhizobium do have a lifespan. I think I read somewhere that if it was left three years in the soil without a host it would die. This isn't strictly true. But one study from Indonesia (on soy) showed that the number of nodules was greatly reduced if you don't apply every year. So I've heard mixed messages about how long they last in the soil. We all have native rhizobium in the soil too. Some of these can set nodules but not fix nitrogen as well as what you would buy. Basically the redder your nodules are the more nitrogen was set. If they are totally white (not even a little pink) not a lot is happening in nitrogen fixation.
ReplyDeleteYou scared me for a second! I see those nodules all the time and I had been thinking that they were "good". I've already planted my bean seeds, but I forgot innoculate. Is there a way to apply if after the seeds are planted? Is it really necessary if I used a lot of compost?
ReplyDeleteNice information.
ReplyDeleteThanks.
Interesting! I have never tried inoculating before, I should give it a try.
ReplyDeleteThank you for the informative post, if I see nodules on my legume roots I won't freak out thinking it's some kind of disease such as clubroot or something like that.
ReplyDeleteThomas, I'm not sure just how much the next crop will benefit, but the favas certainly benefitted, they grew like crazy.
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Christina, I almost left the roots in this time. I cut the plants down to the soil line but what was left was still quite big and I decided that I didn't want to have to deal with planting around and in between. And the favas were regrowing a bit so I decided the roots were going to benefit the compost bin.
Favas are supposed to be great for "green manure", but you have to cut them down and turn them into the soil just when they start to bloom. I could never bring myself to do that, I want those beans.
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chaiselongue, You should do a web search about nitrogen fixing legumes if you really want to learn about it, I barely touched on the subject.
I'm glad you like the new look, I think it's easier to read.
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kitsapFG, You're too smart to be fooled by my little joke. :0 I usually leave the smaller legume roots in the soil as well, but I do like to pull a few to see if they had nodules. Those fava roots were just too big, especially since I'm replanting that bed right away.
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vrtlarica, It would be interesting to see if your peas have root nodules without having been inoculated.
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villager, after reading Daphne's comment it sounds like we should inoculate every time we plant legumes.
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Jackie, I'm not sure if the inoculant can be applied after you plant the seeds, but I suppose it wouldn't hurt to sprinkle some on the soil and water it in or cover it with some compost. And I have no idea if the the bacteria would survive in the compost, that's a very interesting question.
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Daphne, Thanks for the additional information. I didn't know about the white/pink thing, the nodules on my plants were barely pink. I sounds like inoculating with every planting is the thing to do, it certainly can't hurt.
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maybelline, You're welcome.
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Dan, Give it a try and then let us know if you think it made a difference. I've been doing it for years now and I can't remember if I noticed a difference or not.
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mac, Glad to be of help. It's nice to know that not all weird growths are bad. Like bugs, not all ugly ones are a menace in the garden. :)
I'll have to remember to finally do that when I plant beans later on.
ReplyDeleteFunny! I was pretty sure I knew what this was, even though I'd never seen it in person. That's what I get for being an apartment dweller and reader and frustrated garden for so many years!
ReplyDeleteHaving recently bought a tiny house in Oakland, and carved out some garden space, I haven't gotten to doing anything as fancy as inoculating legumes. I'm hemoraging money, as it is.