Nitrogen fixing ground cover?

Nope, it shows total source of contamination, which you said lawns and orchards were a bigger source.

where is your source?

your math seems off. You seem to swap back and forth between an per certain area measurement. And a total measurement.

It’s probably best to looking up N yield per acre, and N requirement per acre of tree’s. Since the tree’s shade a certain area, you could maybe reduce the N yield bij 50%.

I don’t see this coming down to only 4.6% of N need being supplied by a complete ground cover from a N fixer.

Where did i say that?

This, like most of your statements is incorrect.

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Which point in specific? On nitrogen fixation by plants the New Mexico State University study Oscar posted is pretty close to the numbers I used. It show some overachiever crops that could pull higher yields of nitrogen. I would stick to the 200 pound per acre as the upper limit, we are talking growing them under a canopy and thus hindering the metabolic processes that fixes nitrogen.

the source saying you need to till to release the sequestered nitrogen in the nodules

Mah bad, that was jcguarneri

if I’m incorrect then prove it. I don’t mind being wrong at all and in fact would make me happy to correct a deficiency in what I think I know.

Look at the study you quoted (I think it was you, UONM), do the math as to how much nitrogen gets deposited on a square foot basis. Then calculate how much you want to deposit on a grown producing tree in need of nitrogen.

Again: my point has been that the amount is not as significant as some people here want to believe.

The study Oscar quoted:

Nitrogen Return to the Soil and Other Crops

Almost all of the fixed nitrogen goes directly into the plant. However, some nitrogen can be “leaked” or “transferred” into the soil (30–50 lb N/acre) for neighboring non-legume plants (Walley et al., 1996). Most of the nitrogen eventually returns to the soil for neighboring plants when vegetation (roots, leaves, fruits) of the legume dies and decomposes.

If you think this quote says anything about tilling having an increased affect on available nitrogen than you need to get your eyes checked. nowhere in the entire article referenced does it mention tilling or that nitrogen is sequestered in the nodules.


Interesting comment on your part.

As long as the cover is alive nitrogen release is at the tune of 30~50 pounds per acre. Once the plant is dead it releases most of its nitrogen.

Tell me; what do you think happens when the plants are tiled under? Do you think that they become underground dwellers, or that, as the clear English of the text states the roots, leaves, fruits, of the legume, dies and decomposes?

the question you pose is a false equivalency. when plants are tilled, they typically die and decompose (not the case with Japanese stilt grass), but your argument is predicated on that being the only way for plants to die and decompose and to optimally add nitrogen. still using the same article you say supports your conclusions, it is stated:

“A perennial or forage legume crop only adds significant nitrogen for the following crop if the entire biomass (stems, leaves, roots) is incorporated into the soil. If a forage is cut and removed from the field, most of the nitrogen fixed by the forage is removed. Roots and crowns add little soil nitrogen compared with the aboveground biomass.”

if the roots and crowns add little soil nitrogen compared with the aboveground biomass tilling is not required to maximize available nitrogen, nor is plant death required. only the incorporation of the biomass i.e. chop and drop. where it is not removed from the field. therefore, the below is incorrect.

back to your original question

maybe not for you, but for me in Maryland where nitrogen fertilizers are limited by law, it is.

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sorry for the thread hijacking. I use some in my veggie garden in a small scale but I don’t test against a control so I can’t say if growth has been positively affected or not. in a general sense it should improve growth but while it has been proven to increase available nitrogen scientifically, home soil tests are often unreliable in determining available nitrogen. best to give it a go yourself and see what happens, or consult your local extension agent.

Read the paragraph before your quote:

Most of the nitrogen fixed during the season is removed from the field as grain. The stalks, leaves, and roots of grain legumes, such as soybeans and beans, contain about the same concentration of nitrogen as found in non-legume crop residue.

To gain the full amount of nitrogen, 200-pound per acre, you have to tile under the whole thing. Chop and drop? you do know that nitrogen, whether organic or otherwise, do have a tendency to leach off and volatize to the surface? That tiny fraction of a pound of nitrogen your fixers created? Poof, most of it just gone into thin air.

I used to live in Maryland, first Laurel and then College Park. Maryland has a very strong horse tradition, there are small horse farms all over the place. Find the ones drowning in horse manure (your average horse shits, I shit you not, around 50 pounds of horse shit a day), then among those find the one that has built a mountain of the stuff, and as such as a ton of cured manure. If you are smack in the middle of the metro area there is a small horse farm around the USDA research land somewhere between powder mill road and research road.

A single 10 pound load of manure (dry, wet will weight more) has close to a pound of organic nitrogen. Once you secure a source you’ll get all the nitrogen you’ll ever need.

But guess what! Out of curiosity I just looked up Maryland’s fertilizer law, it only applies to lawns! Unless there is a local regulation (and we know in Maryland all 20 different layers of organization love to be that special snowflake with their own regulations) fertilizing crops and orchards does not fall under the nitrogen limits. And if it did, well go get some horse manure and use that.

Dude, I think we are all shooting the breeze here. Honestly thank you for making me really think about this stuff.

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Consider a mix of white dutch clover and others the first year. Alphalpa and red clovers do get larger. When you do mow yearly or whenever clovers maintain a higher moisture content so you will need a good mower. Mostly mowing is to get rid of scrub trees and weeds. Between fruit trees consider nitrogen fixers like buffalo berry, seaberry, goumi or autumn olive. Autumn olive is not a problem in Kansas but in other places it can be. Here are more nitrogen fixers Category:Nitrogen-fixing crops - Wikipedia . This is a good article I mostly agree with 40 Nitrogen Fixing Plants To Grow In Your Garden . One of the things I do is breakup the idea of planting all of one thing. Pawpaw have no pests or diseases similar to persimmons and many others. Consider that growing many plants of the same type side by side almost always ends badly. Consider planting an organic orchard by using alternate trees. A first row might be this mulberry ,goumi , pawpaw, autumn olive, persimmon, pear, seaberry. When the diseases or pests show up they cannot move tree to tree easily. Many become a slave to their orchard not realizing the easier way is diversity and proper plant selection. If you do not mow it doesn’t matter much. You might like this Cover crop and mulch recommendations


At this point i honestly doubt that.

We have asked you multiple times for your source or logic. We have shown you ours, You seem to ignore our questions/requests. But demand a much higher level of proof, than your willing to provide yourself.

I still don’t know if you ever actually grew any N fixer cover crop? Or where you got your information from? At this point I’ll have to assume you never grew any, and most of your information/facts/statements seems made up. Or a wrong interpretation or false equivalency of some source your unwilling to disclose when asked about it.

I don’t mean this as a personal attack. I don’t know you. And in other topics you seem nice :slight_smile: But here, I’m opting out of this discussion with you. Because this does no longer seem like a back and forth based on logic, fact or science. But more of a “voice your opinion based on emotion without factual source or argument” And i do not wish to continue that.

Maybe I’m being overly harsh, if so. My apologies. But if it’s true you don’t mind being wrong and you’ll happily correct a deficiency in what you think you know. Please re-read some of the topic and consider your role in it. Looking at your posts as if it was some-one else who wrote them.

If done the same myself.

You seem to be voicing an opinion against a standpoint that’s imaginary.

If not seen anyone but myself make claims about how significant N fixation will be. And my claims have been that it probably won’t eliminate your fertilization needs.

How do you know what people here believe? Or what did people write in this topic that lead you to think they “believe” a certain thing? (significance of N fixing)

I don’t think the amount of N fixed is the only reason for a N fixing ground cover. Or even the most important factor. Even if it does not supply any N to my tree’s. Since it fixes it’s own, it is in less competition with my tree’s. I see a N fixing ground cover as having the advantage of a ground cover, without the disadvantage of N competition.

However i think that it can supply significant amounts of N to your soil/other plants like your tree’s.

since i might have been overly harsh in my previous statement in this post, ill calculate this for you, like you asked. (even though i think you should first provide your own source/proof before demanding any more from others)

Ill look at a nitrogen fixing ground cover like clover. Since that’s what this topic is about.

Perennial and forage legumes, such as alfalfa, sweet clover, true clovers, and vetches, may fix 250–500 lb of nitrogen per acre.

It is not specifically mentioned in the article. But I’m assuming this 250-500 lb per acre of fixed Nitrogen is from a monocrop in full sun. Not tilled under, but occasionally cut (like mentioned in the article). You don’t need to nor want to till perennial ground covers. Unless you whish to remove them.

I’ll look at a mature orchard. Since that’s probably what most people are interested in, and also the harshest comparison for the ground cover. (highest N need) (I’m assuming larger mature tree’s need more N than younger smaller tree’s. I have no direct source for this. But it seems logical.)

From the same institution

Table 1. Amount of N recommended for apple trees.

Age (years) N per tree or per acre

1 None*
2 1/4 lb/tree if growth is poor
3-5 1/4-1/3 lb/tree
6-7 1/2 lb/tree
over 7 150-200 lb/acre

So perennial and forage legumes may fix 250-500 lb/acre
And an mature apple orchard uses roughly 150-200 lb/acre.

These are both estimates (from the same institution, so larger chance other variables are roughly the same)

However the N yield is likely for a full sun monocrop. So lets half that.
Then we get:
N ground cover Nitrogen fix 125-250 lb/acre of N
And mature apple orchard uses roughly 150-200 lb/acre.
So it seems a N ground cover can supply significant amounts of N to the orchard. Maybe even enough to completely supply the tree’s.

Even if we divide the N cover crop yield by 4, it can still supply roughly half the needed N.

This of course does not work if you put a single clover plant under a full size tree. But this topic is about ground cover. And some clovers for example can survive well between the sod. Or can even replace the sod (especially in a home environment where there is no heavy machinery like tractors riding between the rows)

If you would have read what I said I have agreed with Steve and others about the benefits of running a ground cover, just not for nitrogen fixing.

You calculation seems to be wrong because of the following:

  • Cover crops calculation are based on full coverage of an acre; your average ground cover under a tree is much smaller as we like walking under to harvest the fruit, so we are looking at say a 4x4 area, or 16 square feet.
  • An acre has 43,560 square feet. Your under tree area is 0.00033641715 of that.
  • The 200-pound an acre nitrogen fixation of agricultural cover crops is calculated on the premise of the entire crop being tiled under. Why? Because in line with the document you provided (NMSU: Nitrogen Fixation By Legumes)

Nitrogen Return to the Soil and Other Crops Almost all of the fixed nitrogen goes directly into the plant. However, some nitrogen can be “leaked” or “transferred” into the soil (30–50 lb N/acre) for neighboring non-legume plants (Walley et al., 1996). Most of the nitrogen eventually returns to the soil for neighboring plants when vegetation (roots, leaves, fruits) of the legume dies and decomposes.

  • So on a perfect world with full sun (not happening under your tree) you may leach 40~50 pounds per acre. At 50 pounds per acre that means 0.00115 pounds of nitrogen per 16 square feet area.
  • On the 4x4 area under a tree you are looking at pumping 0.0184 pounds of nitrogen. if you tile it under to release the sequestered nitrogen in the entire plant, grains and all that would go up to 0.0736 pounds. But we can’t do that, because tree roots and such.
  • And let’s not forget that just cutting the cover crop over the soil doesn’t lead to a significant deposition of nitrogen as it literally evaporates away.

So there: You are not getting anywhere near 200-pound per acre, and even if you did your 4x4 area would get a negligible amount of nitrogen. the more accurate number (and still inflated if you ask me) would be around .0184 pounds of nitrogen, or under 2% if you are aiming for around .4 pound of nitrogen per grown tree.

At this point I’m done with this topic. Do what makes you happy, we are not talking anything that is dangerous to trees and trees in fact grow in much worse conditions. Me? Once my trees are bigger my ground cover is going to be strawberries and low bush cranberries, maybe small bush beans. That won’t interfere with my usual compost and mulch routine.

that’s not the whole paragraph. it states:

“When the grain from a grain legume crop is harvested, little nitrogen is returned for the following crop. Most of the nitrogen fixed during the season is removed from the field as grain. The stalks, leaves, and roots of grain legumes, such as soybeans and beans, contain about the same concentration of nitrogen as found in non-legume crop residue. In fact, the residue from a corn crop contains more nitrogen than the residue from a bean crop simply because the corn crop has more residue left after the harvest of corn.”

that is a reference to the nitrogen stored in the plant being utilized in fruiting (i.e. production of grain) that’s why you chop and drop prior to fruiting as I already stated. therefore if you grow peas and allow them to fruit and harvest the fruit the nitrogen is lost in the production of the fruit and a chop and drop or tilling would be pointless.

vaporization is the conversion of Nitrogen in the form of ammonium (often present in manure and urea) into ammonia gas. nitrogen fixation converts ammonia into organic nitrogen so you don’t have that problem.

The law is enforced at the retail level. you simply can’t buy it. the retailer won’t give it to you no matter what you say it is used for. its not like the police are enforcing it. plus I live close to the bay and personally don’t want to impact it negatively if it can be avoided.

Sadly, on the surface once it goes into gas form it goes literally up in the air, never having a chance to be converted into organic nitrogen. The most effective way is drive it under where it can be processed and sequestered by bacteria. I have sandy soils, so I have a preference for compost; slow release nitrogen source that the water driven leaching generates a trickle downward flow. Being a tick layer of compost followed by a thick layer of mulch helps reduce a lot of the outgassing.

Do still look at the horse manure option. As I mentioned the slow release paired by sensible watering means that you won’t be pumping nitrogen away from your area. It both fertilizes and conditions your soil. If you then want to put a ground cover on top of it well it would grow really well.

The native Alder tree in the Puget Sound lowlands, is an excellent nitrogen fixer, but unfortunately, most people consider it a weed.

it is here as well. ruffed grouse love it for its catkins and for cover.

I don’t have access to horse manure. Also, my father got a load of horse manure and was never able to grow pumpkins again, it came with a lot of cut worms.

But i do overseed my lawn with clover from time to time. The lawn is greenest where the clover is. And when i mow the lawn a lot of the clover plant is magically turned into mulch and rots into the ground, releasing its stored nitrogen.

I’ve never intentionally planted nitrogen fixers near my fruit trees. (Although i have a lot of vetch, which i like to keep because it has a lot of flowers in a season when the bees don’t have much else to eat.) But i just bought a fresh batch of clover seed, because parts of my lawn need help.

It doesn’t hurt that clover is pleasant to look at and to walk in.