Legume Plowdown - (or Soil Health 101)

[Vader]

What is the value of a legume plowdown as a "crop"?

In other words what revenue is derived from nitrogen, phosphate and other nutrients retained in the soil after a plowdown crop rotation? How many years does this beneifit persist? What is the cost of producing a legume plowdown "crop"? Taking into account the present value of future years economic benefit what is the net value after production costs of the legume plowdown "crop"?

Do we really understand how legume plowdown works? Are we simply incorporating plant matter which ultimately decomposes into nitrogen? Or is it much, much more?

What is the impact on the soil microbiology of this plowdown "crop"? Does it act to feed the soil microbes? How does that benefit crops?

I think that this is a difficult concept because very few of us are trained microbiologists. These are things that can only be seen with powerful microscopes and even then understanding their impact probably requires a PhD. This is sad since our chosen profession as "farmers" is rooted so basically in the health of the soil and the crops that depend on the soil health.

Do we understand the ramifications on soil health as a result of applications of synthetic fertilizers and pesticides? Who has done the research? Who would be willing to pay for such research? Who is providing extension services to broaden the understanding of basic soil health concepts?

I think that some of the answers are located here:

http://www.soilfoodweb.com/03_about_us/approach_pgs/a_01_benefits.html

I ordered the CD and listened to it. I would highly recommend that every farmer in Western Canada or the world for that matter do likewise. It should be considered Soil Health 101 for every person who is in any way involved in agriculture.

[Vader]

CD costs $30.00 US plus shipping and taxes and is available online at:

http://www.earthfortification.com/shopexd.asp?id=22

[lakenheath]

Define plowdown.

What type of legume?
When do you plant and at what time do you incorporate?
What about available soil moisture usuage?
How does a person prevent soil erosion after a plowdown?
Crop Insurance requires a plowdown to be done before June 15. How much nitrogen has been fixed by then for a spring seeded legume such as peas?

[Vader]

"What type of legume? "

Any legume but alfalfa and clover fix the most nitrogen. Cheaper to establish clover but can take a lot of moisture out of the soil. Peas are more shallow rooted and take less moisture. You can intercrop the peas with a cereal to maximize the biomass production.

"When do you plant and at what time do you incorporate? "

If you are planting clover you should underseed it to a cereal the previous year. Incorporation time is a balance between maximum biomass production and moisture retention. Somewhere between June 15 and July 15 would be my guess. I don't have much practical experience. I am trying to learn as much as I can as fast as I can by reading on the internet and asking questions.

"What about available soil moisture usuage? "

Can be a problem!

"How does a person prevent soil erosion after a plowdown? "

Wind erosion should not be a problem with the amount of biomass being incorporated.

"Crop Insurance requires a plowdown to be done before June 15. How much nitrogen has been fixed by then for a spring seeded legume such as peas? "

Sorry I don't know the crop insurance dates. I thought that to qualify for summerfallow you had to work the field no later than July 15. June 15 would not allow much time for a spring seeded crop like peas to fix much nitrogen. I think that maximum nitrogen fixation has some correlation to time of flowering.

June 15 might be a good date for clover in its second year. Depends on the growing conditions. A late spring might not give a lot of growth even for clover. If you have an early dry spring might make you want to plow down early.

More questions than answers. The universities should be doing more work on this.

[FarmRanger]

I remember being at a SACA (Southern Alberta Conservation Association) conference 2 or 3 years ago and someone mentioned “mowing clover” in late June, I believe. The basic gist was that you did get some nitrogen fix, and good cover for exposed soil, good weed control, no negatives that come from tillage, and I think he said there wasn’t much penalty in lost moisture compared to regular summerfallow. I’ve been tempted to try it, but am afraid to do it on a very large scale with my 5’ mower.

[lakenheath]

But would you get the nitrogen cycling process going fast enough for the next year's crop without incorporation.

[FarmRanger]

I think you had to have good worm numbers in your soil. Those critters actually come to the surface and drag residues into the soil. Millions of little incorporators. I wish I could remember who made that presentation and more of the details. Jill Clapperton maybe?

[lakenheath]

I had heard Jill Clapperton speak. She is a great speaker.

[Vader]

The presence of earthworms is one indication of a healthy soil. They would not be present were it not for the existence of a substantial population of smaller soil organisms starting with the bacteria and the fungi and then moving on up to the flagellates, amoeboe, cilia, nematodes and microarthropods. If you destroy all the little guys then the earthworms are less likely to thrive.

[lakenheath]

July 11th is the deadline for incorporation of a green manure for Saskatchewan Crop Insurance in the brown and dark brown soil zone. July 25th for the black.

[wedino]

Very interesting thread. You've suggested growing your own nitrogen on previous threads, Vader. Have you figured what the cost per lb. is to produce it(N)? How do you replace phosphorus?

[lakenheath]

Jumpstart, Tagteam. Read thread in marketing "Organic"

[wedino]

Cost / lb to "grow your own nitrogen"?

[lakenheath]

Can't quantify something like that. You can try, but it would be very difficult. A good crop of clover can fix over 100lbs of N per acre. So I would say very cheap.

[Vader]

How seriously have we considered the challenge of growing a "crop of nitrogen"? How much research has gone into maximizing yields?

How do you establish the value of the nitrogen? Is a pound of nitrogen from green manure equivalent to a pound of nitrogen from anhydrous or urea, or is it more valuable? Does a pound of nitrogen from green manure give you more of a "kick" than synthetic fertilizer and if so then why?

Is nitrogen the only benefit from green manure plowdown? I don't think so. What about soil organic matter? What about soil structure? What about the water holding capacity of the soil?

Perhaps some areas of the country are more suited to green manure than others. What factors are most important in assessing the effectiveness of a green manure rotation? Average annual rainfall? Soil type? Temperatures? Soil pH?

Some of these questions have probably been answered in much more detail than I am aware of. I am a novice when it comes to soil science. I am very open minded. I am willing to learn. Most of all I am looking for solutions to the crisis in agriculture.

I suspect that we farmers have much opportunity to impact our own future. Some parts of that solution are entirely within our own control. So parts of the solution require collaboration and cooperation. I don't think that we should throw cold water on any idea unless there is a body of proof that it is unworkable. Even ideas that were tried and didn't work in the past may work now with new technology or different circumstances.

If green manure plowdown can be considered a "crop" then what is stopping us from doing it in 2006? Is it a lack of cash flow? That is the response I get most often when I talk to farmers about this idea. They say that they need each and every acre of their farm to produce revenue every year. Perhaps this is a situation that requries some government intervention.

The government has put $750 million dollars on the table in an ad hoc program right now. What if there was a small "string" attached to that money? What if the government said for each $100.00 you receive in this ad hoc program you must plant one acre to a green manure crop. That would force 7.5 million acres into green manure this year. That is equal to about 15 percent of Western Canada's cultivated acres. At one tonne per acre of grain it would represent 7.5 million tonnes less grain going into the export market. I know that is a small percentage of world production but the world surplus of grain is not really all that large. It is just large enough to depress prices. The world has eaten its way through more wheat than it has produced for four of the last five years. I think that 7.5 million less acres of grain available for export from Canada would have a significant impact on prices, particularly if the program were extended for three or four years.