As I understand it as long as you are tilling compostables near the soil surface its not a problem. Its when they are buried deep that anarobic decompostion occurs and thats not so great. Do keep in mind that decomposing grass uses nitrogen and that would come from your garden soil and also if these are grass clippings containing seed heads you are sowing grass seed in your garden. HA!!! If you are anything like me it would be best to throw that grass on a compost pile. I admit I'm slow to get out there and cut the grass so I KNOW mine contains loads of seed ;o)
Mike

Why would decomposing grass clippings use nitrogen from the garden soil? Fresh grass clippings, as I understand it, contain a large amount of nitrogen of their own and will jump-start a coimpost pile. So what's different in the soil?

I could understand it if the question was about wood chips or dried oak leaves, perhaps.

I scratch fresh grass clippings into the top few inches of soil where seeds will be planted. Theye rot in no time, help make a loose, friable soil and their nutrients are released right where seedlings will find them.

Wayne in the Adks.

Adding fresh clippings to soil is a perfect way to feed those microorganisms and to add a little bit of nitrogen to the soil. The decomposing bacteria are in the soil....therefore you MUST incorporate the clippings in order to facilitate the process. By the way, grass is mostly water, and has a very low C:N ratio; somewhere around 15 to 20, depending how much you fertilize.

The only problem with grass clippings would be if you are adding a HUGE pile all at once. Then, that anaerobic process kicks in and you end up with a stinky mess.

The best option, of course, is to not collect the clippings at all, and let them recycle back into the soil and lawn!

>The best option, of course, is to not collect the clippings at all, and let them recycle back into the soil and lawn!

Rhizo_1, I know is's not sustainable, but there are a lot of us who see a lawn only as a source of organic matter for the garden. Ok, it also serves as a fire barrier between the house and the forest. I hear that there are some who grow a lawn for other reasons. :)

Wayne in the Adks.

An acre of grass will suck up more Carbon Dioxide and release more Oxygen than will the same acre of trees, it has to do with the number of plants working at doing that.
Using fresh grass clippings as a mulch will not "steal" Nitrogen from the soil and will in reality add N. The most bestest way to use grass clippings is to recycle them back into the lawn, but if you do collect them, use them as a mulch and don't till them into the soil, let the soil bacteria do that for you. Much less work for you, and while they are present as a mulch they will aid in suppressing weed growth, aid in keeping the soil cooler (unless you put too much down and they start to digest and heat up), and they will aid in conserving soil moisture, all major benefits. Some few weeds may grow from the grass but they are always easy to pull out, unless you let them grow too tall and root too deeply.

Kimmsr - I would REALLY like to see some research to back up that first sentence. Trees sequester carbon in their wood - grass doesn't have a lot of wood. The MASS of an acre of trees is several orders of magnitude greater than the mass of a mown lawn.

Don't understand how this could work.

Hmmm. I don't know the actual figures regarding trees versus grass, but one thing is for certain. Grass is a very short term absorber of CO2 while trees (and the oceans) are the primary storehouses. Stored CO2 in grass is very shortly reconverted.....back into CO2. Lawns are certainly oxygen producers, and a vital component of the water, carbon cycles.

But I sure do believe that grass clippings should be returned back to the soil, thereby creating a much more succulent and sturdy fire barrier.

Okay, I'm new here, but I have used grass clippings in my garden since 1972, so I have a little experience.
Some things I know are not true are that grass clippings will "steal nitrogen from the soil." They contain about 4% nitrogen,more if you have clover in the lawn. It does make a difference whether you till them in or leave them on the surface. Tilled in, the microbes that break them down are cut off from the inexhaustilbe supply of nitrogen in our atmosphere. Some free living microbes, as well as the ones living on the roots of legumes, can take nitrogen directly from the air.

Another thing is that you simply never have to "dig them in." I've left my clipings right on the surface for over three decades, the way nature has done with organic materials for millions of years.And they've produced all the following benefits year after year:

1. They eliminate weeding, permanently. You don't even have to pull weeds already in your garden, even if they're taller than you. Just trample them flat and cover them with a good 3 or 4 inches of grass clippings. If you can't get many clippings at one time, either just do small areas each time you mow, or use newspapers to stretch a limited amount of clippings. Wet them, lay them down first, then cover with enough clippings to hide them. Don't use slick parts of the paper with a lot of color in them. There's debate over whether the ink is harmful.

2. You will need no other fertilizer, ever. I haven't spent one cent on fertilizers in 34 years. The grass clippings will supply all the nurtients your crops need, and better than any chemical fertilizer can.

3. The clippings will transform the worst soil- clay or sand- into the best. It's hard to believe the black, fluffy, fertile soil I have today came even from the same planet as the horrible heavy red clay I started with.

4. The clippings will conserve water by virtually eliminating evaporation and keeping the soil much cooler. Cooler soil means cooler plants, which means less transpiration- plant sweating.

5. The clippings will lead to an explosion in the populations of soil microorganisms and earthworms. I bought 500 "red wrigglers" in '72 or '73, and I've given away many times that many since, with tons still left in my soil.The clippings provide not only an ideal environment for them, but an inexhaustible supply of food.

Oh, on the debate of CO2 absorption by grass Vs forests0 kind of not relevant to here- I read an intereting article in Discover Mag over a year ago. It's been found that forests are actually not a net sink for CO2. They give off just as much, in the decay of organic materials on the forest floor, as the trees themselves absorb. But that certainly should never serve as an excuse to cut them down like we are all over the world. They have many, many other benefits.

If anyone doubts any of the above- and I admit it "sounds too good to be true"- simply test it on part of your garden or even a single plant.I know you'll be amazed at the result.

I am a religious user of grass clippings. I mulch with wetted newspaper then pile high with fresh grass clippings before I plant. Add more grass over the course of the summer--no weeds, roots don't burn, excellent C/N to till in in the fall.

However, it has always been my understanding that fresh grass clippings temporarily locks up a small amount of usable nitrogen in its decomposition process. The amount is negligible and the period brief, but true nevertheless. Not enough tochange one's habits.

I compost most of my grass clippings after the initial mulching and bury my kitchen waste in the overheated pile. I make over 1 ton of compost a year, primarily from grass clippings.

maupin, can you give a good reason that you do this?

"excellent C/N to till in in the fall."

I mean the till in "in the fall" part? Why do you think that is needed, better than just leaving everything on top of the soil?
I've given people a multiple choice question sometimes:
Where do you think is the Worst soil in the world:
A. The Sahara Desert
B. The tundra in the Arctic
C. The Amazon Rain Forest
D. Your backyard

Though some people say their own yard, no one ever picks C, which is the right answer! Yes, that astounded me,too, when I first heard it. The reason there is that incredible growth there- despite having the worst, least nutritous soil on earth- is that nature continually mulches. And the materails are never dug in, just new layers added on top year after year, decade after decade.
It's worked for nature for millions of years, so why not do the same in our gardens?

You also said:
"However, it has always been my understanding that fresh grass clippings temporarily lock up a small amount of usable nitrogen in its decomposition process. The amount is negligible and the period brief, but true nevertheless. Not enough tochange one's habits."

I think the best, simplest way to tell if something is even temporarily locking up some nutrient is to look at the plants. In all the years I've used grass clippings, and every time I've seen other people use them, I have never seen the slightest, even temporary symptom of nitrogen deficiency in plants. On the contrary, sickly, yellowish plants within almost hours start to turn a much darker, healthier green, a sure sign they are getting all the nitrogen they need. I think you are right on that this is simply nothing to worry about.

Tyrell

Just one more testimony that my fresh clippings have not seemed to tie up one bit of nitrogen! I used to be concerned about this but learned about the factor of whether or not they're worked in. In fact, I then read the same thing is true with wood chips- OK if they're just on the top of the soil- so I risked that too. The principle has held true for me- first year in the gardens where I am now and I have a ridiculous amount of jungle growth and loads of rich green color- I only wish a bit of the nitrogen HAD been tied up around some things!! In the future, I'm convinced I don't need to let stuff age if it's just placed on top! Let it do it's aging right in the garden...

I use freshly cut grass clippings tightly packed in a half plastic barrel then covered with compost and have had great success growing my seed in this way I have sowed tomato seed and in just a week the seed has germinated what happens is when the grass start to decompose it heats up and also heat the compost and seed will germanite in only a few days just keep the compost moist with a sprinkle of water each day