But don’t the roots of the host plant take up the nitrogen that the nitrogen-fixing bacteria fix? If the host plant is taking up the nitrogen, doesn’t the host plant need to be killed or partially killed (e.g. mowed) or something like that for any other plant to derive any substantial nitrogen benefit?
Clover plants are renewing all the time, its not permanent plant structure. This is even for the perennial ones: there is a lot of dieback over the winter or in dry weather etc. So even if you don’t mow it you are getting lots of organic matter into your soil from the decaying plant matter (both roots and tops). Its not clear if N is directly going from living clover roots to other plants, I could find no firm answer either way on that one but some people seem to think it does. Note I found an article stating that most of the added N in fact comes from the decaying tops, not sure why the above article was implying otherwise.
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as you say, nitrogen provenance (roots or tops) depends on external conditions. if you scythe/graze a clover plant during the growing season, it will have to kill some of its roots and push other roots more deeply in the soil to answer the emergency. The energy of some of the killed roots will be used to make new tops. The nodules attached to the killed roots will be fertilizer, and the killed roots themselves earthworm channels eventually.
If you allow natural death of the tops at the end of the growing season, the roots will not die, but arrange to store energy and nutrients other than N, and most of the N will be from the dying tops.
I could see, about a year ago, a paper showing that grass and grapevines were exchanging nuclear-labeled nitrogen in a vineyard. But mysteriously, grapevines and alfalfa were exchanging almost zero N so experimentally things are not crystal clear.
IMHO, what happens with the russian olives is, they do not withdraw their N from the leaves at the end of the season, into the roots and trunk, because it is so cheap, and the dead leaves have more N compared to regular leaves.
Ross,
I’ll do my best to answer your second question. My understanding is that you reap more of the nitrogen-fixation benefit if you “chop and drop” as opposed to just having a nitrogen-fixing tree (NFT) growing. I believe other plants only get the benefit of the fixed nitrogen via annual leaf drop (though perhaps some is shared via mycorrhiza). There’s a guy in my area doing more of a Mark Shepherd-style (Regenerative Agriculture) tree farm on 160 acres (chestnuts, hazelnuts, many other species) using leguminous pasture between his rows that get grazed/mowed which he believes makes much more of the fixed N available to his trees (since periodic cutting/grazing of top growth causes similar root die off (not to mention the top growth either rots in place or is processed and deposited in manure). I didn’t include NFTs in my orchard but have red, white and sweet clovers, alfalfa in the pasture between my tree rows and some shrub legumes that I chop and drop for this reason.
Oops, I see now several others have already answered this question.
If there’s much nitrogen in leaves, wouldn’t a lot of it got lost into the atmosphere rather than getting incorporated in the soil?
I don’t see how it would be lost to the atmosphere. I’m not sure I am understanding your question.
some will be lost. composting (in open air) loses of order 50% of the original nitrogen. An important source of natural composting is earthworms. If a narrow russian olive leaf is dragged 2 inches into a burrow and ground right there by the earthworm, then very little N will be lost.
How many seasons of success are you talking about here? I think it is risky to assume cause and effect on limited trials but I’m very interested in the possible efficacy of neem oil. My Lorsban is almost out and I really don’t feel like purchasing another 20 years supply. To me, that is the only downside of such a local and limited application of most any poison. Anything you can virtually paint on a spot is an extremely reduced exposure, and a single app of Lorsban lasts a year. How exactly does this adversely effect the environment or one’s health, I wonder.
But who wants to store a kilo of Lorsban? There’s where the danger lies, IMO.
This is my 2nd year. One reason why I am so positive on it is I had borers on the majority of my trees until I started using it. Many other treatments were tried and failed completely and for about five years I was spending a great deal of time digging them out. I have only had a couple infections (as in two per year) in the last two years.
I might get out today and apply this winter’s coat. I have had really good results from winter treatment.
Note I recommend this only on stone fruits in 3rd or greater leaf, also I would apply only in cooler months. This is to minimize bark damage. I have been meaning to experiment with it on apples. I have used it on young peach trees with no bad effect myself.
Hi Scott,
I am a visual learner. Would you mind posting pics of how you apply neem on the base of those trees?
I am considering it for next spring. Thanks.
OK I just hit all my trees and I took a picture:
This is the apricot tree on peach that I had missed earlier. I put the neem in the cup and just blob it all around the base with a paint brush. Its good for it to run into the ground, that gets the neem lower where the worms are.
While applying I found three more trees that had worms, so that makes about 10% infected total.
For last years and this most recent application I have been using the wrong kind of raw neem, you want the cloudy stuff with the very strong nutty smell. The original treatments I did were the cloudy stuff, stuff I have been using more recently is clear. I don’t think it works nearly as well as the cloudy stuff and may explain how I have a few more infestations. You need to microwave the cloudy stuff for a bit to make it liquid, it solidifies when stored in a cool garage.
I just ordered a bottle of the original stuff I was using which I know is good, from Neem Resource, and am going to do one more application later this winter with it. I think the Dyna-Grow oil is also the good stuff. If you read the reviews of dyna-grow there is a long one which has side by side pictures of the clear (substandard) stuff and the cloudy (good) stuff.
While painting I treated one G11 apple tree as a test to see how it fares.
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Thanks, Scott. Great to see how it’s done. Thanks for a very detailed explanation.
This thing is not cheap 
Yes it is expensive. It could probably be cut 50-50 with water to extend it and I may try doing that in a few years. Right now I just want to get rid of the borers, they nearly wiped out my peach orchard a few years ago and I want revenge.
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How cold would the weather be when you would stop applying it in the winter?
32F and below?
It probably doesn’t matter much, unlike spraying there is no freeze issue. But it would be easier to do on a warmer day since the neem will stay liquid easier.
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Scott- Did latex paint or latex plus joint compound fail to prevent peach borers?
Thanks for posting your results. Getting 90% none infected rate seems really good especially for a mostly organic approach.
I get about those results with no spray here.
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Everything is place specific. Thanks for sharing your experience, Scott. Regarding beneficials, biodiversity is key. Not just one or two species of plants that may (temporarily) attract beneficials but a food chain lasting an extended period and don’t forget to provide overwintering habitat. Despite the fact that I live in the middle of a giant field of corn and soy (Iowa) our property has ~60 acres of timber and thousands of trees, and hundreds of flowering shrubs have been planted on the field and pasture acreage by my MIL over the last 20+ years. I’ve seen more insect life here than anywhere else I’ve lived. And I’ve only identified a small portion. I feel fortunate for that (and I hope it works in my favor - I read a good article about how much more successful organic orchards were that were bordered by native forest, will try to find link). Iowa was the second to sixth largest producer of apples until the Armistace Blizzard of 1940 and I don’t think there were many chemical sprays back then (besides Bordeaux mixture probably being used for scab). The local landscape was obviously more diverse then when farms had crops and livestock and hedgerows and more trees. Standard rootstocks may have had a significant benefit as well (there’s a 30’+ wild apple tree in a fencerow about 1/2 a mile from our place that produces decent, sweet apples that are unblemished and tree seems disease-free). Despite my lack of orchard experience in this climate I remain hopeful and will keep you guys posted. However, I’ve got a 13 year old orchard in SE Texas (near Houston) and I highly recommend citrus, figs, persimmons, pomegranates, black mulberries, blackberries for low-maintenance, no-spray harvests, though low-chill temperate fruits do fairly well too. That orchard hasn’t had any irrigation or maintenance in 11 years except mulching with ramial wood chips about every other year and some minor pruning when I’m back for Christmas.
Thanks for everyone sharing their thoughts and experience. It is very valuable.
Cheers!
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