Settle a question for us....

I want to grow a green manure on the garden, kill it with black plastic, then plant thru the dead green manure, using it as mulch.

My wife says green manure makes no sense. She says the law of conservation of matter means that anything you grow on the garden will not add anything to the soil. She says that you have to bring stuff to the garden to add to the mass.

I think the sun puts energy into the equation, so the soil can be helped by green manure, and that the total mass of the garden will be increased just like bringing stuff into the garden.

I dunno if I'm clear enough in my explanation, but is there anybody interested in commenting?

Your idea is a sound idea. I would think digging them in would be advantageous. You might have to mow them down before placing the plastic.

http://www.johnnyseeds.com/catalog/subcategory.aspx?category=289&subcategory=291

I don't know how much time you have to grow a cover crop before planting this year. You could start this project this August after you start pulling produce out. Note that I have never used a cover crop: I did buy a pound of buckwheat seeds for fifty cents on a notion last year. I would be using that as a smother crop.

It is beautiful and grows easily, then is easy to till in. It is an annual, and doesn't take over like red clover can

I learned that buckwheat attracts beneficial insects.
http://books.google.com/books?id=NdEPSUWNB7sC&pg=PA146&lpg=PA146&dq=Buckwheat+gardener&source=bl&ots=Vr4NOPb0kH&sig=2x3R9pgrnDGumswodcG6-W7DBbk&hl=en&ei=WR7vSbupHJT4MJP11PUP&sa=X&oi=book_result&ct=result&resnum=4#PPA150,M1

"Cover crops epitomize sustainability and are grown specifically to return to the soil what was removed with the harvest. Converting air and sun into vital organic matter, cover crops feed soil organisms, which in turn nourish plants. They also improve soil tilth and structure, reduce soil erosion, suppress weeds, and in the case of legumes, add nitrogen."

I believe some do use them as you were suggesting so that they have a no till garden. That is what I am going to head for next winter with a cover crop, to fix some nitrogen and try to get to a no till garden.

Seeds Of Change http://www.seedsofchange.com/garden_center/browse_category.aspx?id=336

I bought most of our seeds from this website and so far we have almost 100% germination.

There are several reasons that a green manure might add more than what it removes from a plot of soil. And i do not believe it is only through it's processing of the sun's energy. Plants also attract life. This also adds to the improvement of the soil IMO.

Plants also absorb water (and nutrients) from a greater area and when they are turned back into the soil, further enrich the smaller area.

& I've lived here almost 8 years! :o

dg

All plants need water, potassium, phosphorus, nitrogen, and carbon.

All plants take up water, phosphorus, and potassium from the soil.

Some plants take nitrogen from the soil, and some plants take nitrogen from the air.

All plants take carbon from the air, and use the carbon to build cell mass and perform other valuable functions.

Green manure crops are plants that take nitrogen from the air. If you grow these crops, and till them back into the ground, you will add nitrogen and carbon (which were formerly in the air) to the soil.

You're right, your wife is not.

makes NO sense, but that green manure adds NO additional MASS to the garden. It may add nutrients.....change the molecular content of the garden, but it does NOT add net mass. Sunlight changes the molecular nature of stuff, but it does not, I think, add to net mass. The net MASS of the garden remains the same? Ms Bigmack

...and leave nitrogen and carbon in the roots that are not pulled out at the end of the season.

Please don't use black plastic. You're adding a very un-green material to a green environment.

I'd cut it down or mow it and leave it in place if I weren't going to turn it under. Favas are my principal cover crop and if I let them grow to maturity the stalks would become a straw-like mulch if I used them the way you're suggesting. I've never done it however.

is a common mistake that people make about plants. They think that most of the matter that becomes a plant comes from the soil.

It doesn't. Most of the matter that becomes a plant comes from the air and water. The basic reaction is that CO2 plus water plus energy is converted to various carbohydrates. Some are sugars. The sugars in turn are strung together into long chains of starches and eventually tougher hydrocarbons like cellulose -- the basic building block of plants.

So green manure actually adds a pretty massive amount of mass to the garden which has been captured from the CO2 in the air.

The soil provides the other elements needed to make proteins and other plant material -- primarily nitrogen, potassium and phosphorous. Calcium is provided by limestone and similar minerals. The reason it seems that fertilizer has such a remarkable effect on plant growth is that these elements are in much shorter supply than CO2 and water, and are the limiting factors in plant growth.

When you plow this stuff under, it creates a better soil eco system for worms, fungi and other micro-organisms that help break down even more minerals and nutrients locked up in the soil. These creatures are eating the carbs for energy.

I would agree with others though that you don't want to put black plastic down. Turn the green manure into the soil so you create an active eco system, which black plastic can suffocate.

I really like the no-till system. Haven't used it for years. But with the Bush Recession......

I don't want black plastic, but I do want to kill the cover crop. How about "landscape cloth" to do the killing?

I'd just remove it in the spring and plant thru the dead cover crop.

Re-use the landscape cloth next fall, of course.

Your plan raises a lot of questions.

It's too late to use green manure for this spring, so are you talking about a plan for next year? It sounds like you're planning to plant the green manure now and plant your veggies next spring?

Are you physically fit and able to till it under? Because the best thing to do with green manure is to till it under. That's because it has to be covered by soil for the worms to eat it. Worm "casings" (worm feces) are one of the best components of soil. The green manure captures energy from the sun, and puts it under ground where it fuels a vibrant eco system. Killing it on the ground with a plastic or cloth cover doesn't do very much except give the eco system some dead roots to eat. No till has huge advantages for the larger farm eco system, but it's pretty challenging for the small scale gardener. If you are concerned about the effects of tilling, you can take steps to manage run off and erosion.

Another way to avoid having to use a cloth or plastic to kill the green manure is to use certain annual grasses. The problem of green manure that you seem to be referencing is that it becomes a weed, and killing it is difficult. Iirc, there are certain grasses that you can plant in the fall and that don't grow back in the spring. I think it's rye grass, but I'll check one of my gardening books.

If you are completely dedicated to no till you might try a method that doesn't use green manure, which one way or another has to be killed. You can get hay or some other rapidly decaying mulch, put it down very thickly and plant through it. It has to be a hay or straw that won't take seed in your garden and become a weed. Here on the east coast, I think they use something called marsh hay. Because it only grows in salt water marshes, it won't take seed in the garden. It slowly decays, fertilizing the soil, supporting the micro eco system while preventing weeds from getting sunlight.

For garden paths it is several layers of newspaper then chips on top. To make hard ground soft, I put down newspaper, then sand. Actually I used Mt Poop, the sand/manure scrapings from the bottom of our chicken run.

Some plants add a lot of nitrogen to the soil.