Questions: If I layer grass clippings or coffee grounds over leaf mulch, will the nitrogen "disappear" (do the clippings need to be mixed with or buried under leaves?) Q:Can I mix the coffee grounds directly into the soil around my spinach and kale?

A: Yes. You can also topdress with a little of it (too much sometimes repels water).

Q: Can I use a layer of coffee grounds over newly planted seeds?

A: Yes, but only a sprinkle. Too much- again- will repel water- or act as a mulch that prevents sprouting. I wouldn't use them in this way in indoor plants/flats where you might get damping off.

Q:I usually just bury my kitchen scraps and spread the leaf mulch and grass clippings and coffee grounds over my garden, but am I wasting some of my compostables if I don't have a compost pile?

A: Well, you do lose some N to the atmosphere if you put greens on top like that. It sounds like you have extra greens- which could be put into a compost pile with shredded leaves, shredded paper, etc. If you continually have more greens, then no big deal.

Q: What are the relative benefits/nitrogen content of grass clippings versus coffee grounds?

A: I believe that grass has higher N content, but it will lose N if left on the surface to turn brown. Coffee grounds (2% N?) are great because their physical form allows us to mix, spread, topdress, etc without suppressing growth as a mulch of grass might (unless we're talking about evenly mulching grass back into the lawn as we cut it). Coffee grounds will lose N as well, but it doesn't last very long in warm weather on my lawn anyway.

Have you thought about leaving your clippings on the lawn when you mow? I've just gotten into this whole area and have read a lot of positive things about 'grass-cycling'.

Sounds like it reduces fertilizer needs for the lawn. If you cut often enough then you don't have a problem with loose grass in the yard - it goes away pretty quickly.

I seem to have too many greens and I'm planning to do this this summer to keep things in my compost bin balanced. Plus I kind of like the idea of not having to drag bags of grass around the yard.

Just plunk that on your soil as a mulch and the Soil Food Web will move it into the soil for you, no effort required on your part except plunking it down. If you mix too much fresh grass clippings into that you may get a somewhat offensive odor indicating that nutrients, mostly nitrogen, are gassing off to the atmosphere and the best way to counteract that is to put down some high carbon material over the rest of it.

Quote:Well, you do lose some N to the atmosphere if you put greens on top like that.

Can someone explain the chemical mechanisms by which one loses nitrogen to the atmosphere? I once found some discussion of traces of -CN radicals being lost to the atmosphere but I have not found any references to any significant nitrogen losses to the atmosphere.

[The references may be there, - "plain as the nose on my face", to use an old experssion. I just havn't seen them.]

I believe that 2 mechanisms are mineralization and denitrification- although they are normally described in soils or water.

In the first- N forms (simple anions, or from proteins) are transformed into NH4+, and NH3 is lost because it is volatile. Normal thermal/ light induced degradation and bacterial action can cause this to happen (going on memory here). In denitrification NO3- is directly converted to N2 as part of the nitrogen cycle. You may remember basic fishtank chemistry where NH4+ --> NO2- --> NO3- . I guess this is the opposite of that.

Going on memory there. However- green leaves turning brown, fresh cut green grass drying out and turning brown- both are accompanied by loss of N as a volatile. I'm sure that autocatalytic breakdown of the proteins in the greens would cause loss of a variety of N bearing compounds. Manures and urine often contain urea, which has a very simple pathway to NH3 conversion.

Denitrification. If you smell an ammonia like odor when near any pile of high Nitrogen substance you are smelling Nitrogen escaping to the atmosphere. That happens all too frequently. Drive by a farm field after they have spread manure and you will smell Nitrogen going up into the atmosphere. Find a pile of manure that is just sitting there with not enough high carbon material and you will smell Nitrogen escaping to the atmosphere. Anytime you smell an ammonia like odor that is Nitrogen loss.

While it might not pertain to this exact situation, you might want to do a yahoo search on "earth kind". Texas A&M has been doing studies on roses and other plants using enviromental freindly care. One of the areas they have worked with is a simple sheet mulching/composting procedure they call a living mulch. It is a simple procedure of layering green shreded leaves and branch waste over the beds and using green ground limb waste to form a five or six inch layer of compost over the bed. They state they use some drip irrigation over their test beds the first year, but no watering over the remaining years of the studies. As the "native" shreded materials decompose, they feed the plants and hold moisture to the plants. I have seen two slide presentations of two different field trails of this type mulching, and the growth of the plants in the trail beds in question was amazing.

This living mulch you speak of sounds like lasagna gardening.

Thank you, everyone, for the information and suggestions. I'll put a layer of leaf mulch over the grass clippings to try to prevent nitrogen loss. By the way, does that nitrogen loss result in the emission of a greenhouse gas? Any better or worse for global warming than gas emitted when "browns" rot? The mention of using shredded green leaves to make a "living mulch" makes me wonder whether the partly decayed leaf mulch I buy each year adds as many nutrients to the soil as green leaves would. And maybe now that I bring home a nice bag of coffee grounds daily, I don't really need to gather the neighbors' grass clippings any more. I hate to see free organic matter go to the landfill, though.

I wouldn't worry about greenhouse gas emissions from that material- what would have happened if you didn't use it? It would die back in the fall and emit the same gas. Take one less drive to the mall and you're covered for the year :)

If really worried about the carbon balance- cut down your trees and vegitation every year and bury it deep in clay (beyond where roots will get to it). You'll be sequestering the C source, and millions of years from now they'll be using it as fossil fuel. Replant, repeat :)

There are some theories that state that harvesting peat moss releases the CO2 held in those bogs which contributes to global warming but it is not very likely that your lasagna bed will, unless you dig it up some time later.