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.