That nitrogen isn’t really made available unless the plant has been turned into the soil as green manure at flower. Harvesting the bean crop (protein/nitrogen rich itself) leaves the soil about neutral, maybe somewhat depleted depending on how the field is cleared and prepped for the next planting. Also, there’s research showing that some corn can fix some nitrogen itself on the slimy exudates of aerial roots.
The whole three sisters thing was an early crop rotation method. Not all together like as advertised.
Beans where grown first as they are shallow rooted and produce about 50% of the nitrogen they need. If they harvest 25% of the crop and till under the rest they have around around a 25% increase in a available N.
The next season is corn and pumpkins together. They are both heavy N feeders. They spaced out the corn a lot more than modern hybrids so the pumpkins had plenty of room to grow and shade out weeds. They unfortunately share the pest of cucumber beetle species (corn rootworm).
The next season they had to go back to beans to break the rootworm cycle.
Eventually other nutrients would become low (P,K, micros etc). Other pests and diseases would buildup. They would rotate onto new plots letting the old plots go fallow for a while.
The Europeans reported the three sisters methodwith some tribes in the northeast. The accounts are all very jumbled and contradictory. The tribes in New England also appear to have have been relatively new to growing. All three species were not found together in New England before the 1300’s. If they did grow them this way they could only do it one season in a location. They would have to change locations then next year.
Fundementally you can’t plant corn/pumpkins repeatedly without a break. It’s a mega attractant to the rootworm beetles which are endemic to North America. If they did not rotate they would have crop failures after only one season. Beans also have all sorts fungal and bacterial diseases. The only way they could control them is via rotation/fallowing.
What was done in mesoamerica for thousands of years was rotation. They were the ones that domesticated the three species and built large civilizations from the extra food availability. They grew bush and vine beans, corn, and pumpkins. They also grew casava, tomatoes, peppers and other species. When yields started to decline, they would fallow the ground and move their plots.
There is evidence that the Mayans for over 500 years mostly figured out how to avoid fallowing their fields. They would grow 3 cycles per year in rotation for a large surplus of food.
In the old world, agriculture started in the Mediterranean and temperate regions. The domesticated species are mostly winter annuals or adapted to a Mediterranean climate (dry summers, wet winters).
New world species are mostly subtropical or tropical species. Corn, potatoes, pumpkins, beans, tomatoes, peppers, etc are all warm weather crops. This is a major reason the large population centers developed in the tropical and subtropical areas.
Populations in the North America domesticated other species like lambsquarters and erect knotweed. However these species were not as productive and they gave them up when corn and beans were traded for from present day Mexico.
So the least experienced farmers with the species, were the first ones the Europeans ran into in North America. :-)
That nitrogen is fixed inside root nodules on the root system of the bean plants. It’s taken up by them immediately. It’s not available to the corn or anything else growing nearby.
There is some priming for other non legumes 30-50 lb/ac (roughly 25 ppm). Not that much for N hungry plants but for general growth/an N starved system (forest Reclamation) that’s pretty reasonable
They really need to update that paper with some better information. That is what you get when you chronically underfund the extension services and all the best and brightest bail to private industry to make more money. I had to pull up the source material the article because my bullsit meter went off.
After reviewing the source material, you are 100% completely wrong :-)
First off the “transfer” of N from alfalfa to a grass was stated in the sourcing paper to be from mineralization of roots. Aka decomposing plant parts.
Perennial species often grow new roots and abandon older roots every year.
Alfalfa will abandon and regrow new roots after every cutting as the plant pulls carbohydrates from the roots to grow new stems and leaves.
The thing is that the grasses will do the exact same thing. Older roots die back and newer roots grow. So it’s more of mutual swapping of N rather than a one-sided legume being leaky.
That nitrogen isn’t really made available unless the plant has been turned into the soil as green manure at flower. Harvesting the bean crop (protein/nitrogen rich itself) leaves the soil about neutral, maybe somewhat depleted depending on how the field is cleared and prepped for the next planting. Also, there’s research showing that some corn can fix some nitrogen itself on the slimy exudates of aerial roots.
The whole three sisters thing was an early crop rotation method. Not all together like as advertised.
Beans where grown first as they are shallow rooted and produce about 50% of the nitrogen they need. If they harvest 25% of the crop and till under the rest they have around around a 25% increase in a available N.
The next season is corn and pumpkins together. They are both heavy N feeders. They spaced out the corn a lot more than modern hybrids so the pumpkins had plenty of room to grow and shade out weeds. They unfortunately share the pest of cucumber beetle species (corn rootworm).
The next season they had to go back to beans to break the rootworm cycle.
Eventually other nutrients would become low (P,K, micros etc). Other pests and diseases would buildup. They would rotate onto new plots letting the old plots go fallow for a while.
Hm. Maybe I need to dig into the Wikipedia sources then because something is amiss here.
[https://en.m.wikipedia.org/wiki/Three_Sisters_(agriculture)](https://en.m.wikipedia.org/wiki/Three_Sisters_(agriculture\))
The Europeans reported the three sisters methodwith some tribes in the northeast. The accounts are all very jumbled and contradictory. The tribes in New England also appear to have have been relatively new to growing. All three species were not found together in New England before the 1300’s. If they did grow them this way they could only do it one season in a location. They would have to change locations then next year.
Fundementally you can’t plant corn/pumpkins repeatedly without a break. It’s a mega attractant to the rootworm beetles which are endemic to North America. If they did not rotate they would have crop failures after only one season. Beans also have all sorts fungal and bacterial diseases. The only way they could control them is via rotation/fallowing.
What was done in mesoamerica for thousands of years was rotation. They were the ones that domesticated the three species and built large civilizations from the extra food availability. They grew bush and vine beans, corn, and pumpkins. They also grew casava, tomatoes, peppers and other species. When yields started to decline, they would fallow the ground and move their plots.
There is evidence that the Mayans for over 500 years mostly figured out how to avoid fallowing their fields. They would grow 3 cycles per year in rotation for a large surplus of food.
That’s seriously fascinating stuff especially as a veg gardener. Appreciate the detailed info and insight!
Here’s a fun thought.
In the old world, agriculture started in the Mediterranean and temperate regions. The domesticated species are mostly winter annuals or adapted to a Mediterranean climate (dry summers, wet winters).
New world species are mostly subtropical or tropical species. Corn, potatoes, pumpkins, beans, tomatoes, peppers, etc are all warm weather crops. This is a major reason the large population centers developed in the tropical and subtropical areas.
Populations in the North America domesticated other species like lambsquarters and erect knotweed. However these species were not as productive and they gave them up when corn and beans were traded for from present day Mexico.
So the least experienced farmers with the species, were the first ones the Europeans ran into in North America. :-)
You’re describing N balance rather than the fixation and conversion of fixed N.
If it’s fixed, it becomes plant available, by being quickly turned into ingorganic forms (primarily No3).
That nitrogen is fixed inside root nodules on the root system of the bean plants. It’s taken up by them immediately. It’s not available to the corn or anything else growing nearby.
And, you misquoted me.
I looked this up, because I recalled reading about some priming effect from the nodules to the soil.
Turns out we’re both a little off but you’re more on target than I was. They talk about it under Nitrogen return to soil
There is some priming for other non legumes 30-50 lb/ac (roughly 25 ppm). Not that much for N hungry plants but for general growth/an N starved system (forest Reclamation) that’s pretty reasonable
They really need to update that paper with some better information. That is what you get when you chronically underfund the extension services and all the best and brightest bail to private industry to make more money. I had to pull up the source material the article because my bullsit meter went off.
https://sci-hub.se/https://doi.org/10.2134/agronj1996.00021962008800050025x
After reviewing the source material, you are 100% completely wrong :-)
First off the “transfer” of N from alfalfa to a grass was stated in the sourcing paper to be from mineralization of roots. Aka decomposing plant parts.
Perennial species often grow new roots and abandon older roots every year.
Alfalfa will abandon and regrow new roots after every cutting as the plant pulls carbohydrates from the roots to grow new stems and leaves.
The thing is that the grasses will do the exact same thing. Older roots die back and newer roots grow. So it’s more of mutual swapping of N rather than a one-sided legume being leaky.
K