This question may be more appropriate for the turf section rather than the compost section, but here we go:

Is nitrogen "consumed" or "released" during the composting process? It seems like I have heard that putting uncomposted material into a flower bed will rob the nitrogen from the plants, where as I have heard that it is good to put compost on turf or in beds because it contains nitrogen in a "slow-release" thing. This seems to complicate the issue of whether or not to let lawn clippings fall back into the lawn or to catch them. If the clippings are "fresh and uncomposted," and they consume nitrogen as they decay, isn't that taking nitrogen away from the lawn?

This is confusing to say the least. Please help me understand the chemistry/science behind this.

The key to your question is whether you put partially composted or raw materials into or on the area in question. Only fully composted materials should be mixed into soils. Partially composted or raw materials (grass, mulch, etc.) go on top of soil.
Hopefully the Captain or someone else can elaborate on this subject in more detail.

A good point about on v/s in - certainly nature's process yields a "layering" effect of increasingly decomposed material as you get deeper.

I still want to know more about the nitrogen question, though.

KHWOZ basically answered the question. I just want to add on to what has already been said.

Keep in mind that soil/composting microbes have dietic needs that concern carbon and nitrogen, or proteins and carbohydrates, etc. This is the classic C:N ratio.

When compost is "done" the C:N ratio will be between 25-30 to 1. Humus is the absolute end product of all old mature compost. Humus has a C:N near 10:1.

When mature compost is mixed in the soil, the soil microbes spend more time releasing the insoluble nutrients locked up inside the humates in the soil, and converting them into soluble nutrients to plant roots to uptake. This is the best optimal case for gardening.

When "raw" uncomposted organic matter are mixed into the soil, soil microbes have to rob extra soluble nutrients that growing plant roots would normally get, in order to satisfy their appetites and reporoduction needs. If too much soluble nitrogen is mixed in the soil, the microbes steal extra carbon forms from the soil into their bodies. If too much high carboneous matter is mixed into the soil, the microbes steal extra nitrogen from the soil into their bodies as they grow and breed. This situation is not good for gardening!

When uncomposted organic matter (mulches) are placed on top of the soil, and the topsoil below is rich in mature organic matter like humus or mature compost already, there will not be any pH issues, or temporary nitrogen deficencies, etc. near growing plant roots. The soil microbes have their diets met, and the C:N ratio is already balanced and fine underneath the mulch.

If you are not sure about the compost that you have mixed into your soil underneath, you can speed the decomposition while balancing the C:N ratio, by adding good biostimulants as foliar/soil drenches to your crops.

Good teas made from either compost teas, seaweed, or sugary dry molasses flavored compost tea recipes, can help increase good soil microbial activity and growth, and reduce any nutrient deficiencies in crops.

Thanks Cap'tin for clearing that up for us. Now we all know that finished compost is best for 'under the soil' and partially completed compost is best used a mulch. That's the way I do my garden.

CaptainCompostAL, you 'da man! and my composting hero Excellent post, as always. You are one of the true assets to this forum. Keep those instructional posts coming. <insert thumbs up emoticon here>

Thanks for the support my friends!

Happy Gardening!

Again the good Captain reinforces why no-till gardening works for those of us with bad backs and no tillers. The older material has broken down and become a part of the soil underneath and the newer material stays above the surface, slowly biodegrading normally and becoming a part of the lower levels as in nature's program. The liquid compost or nutrient drenches support the process and make it work. There's always more than one way to achieve success. Aren't we lucky He planned it with such versatility for us?

Kathe

I think compost is best under the mulch, but on top of the soil. How deep were you thinking, Captain?

I usually put 4-6" of my slightly unfinished compost, down on top of the soil for an average mulch on almost all of my veggies. When many heavy feeders like sweet corn and tomatoes grow a bigger, I add another 4-6" more of unfinished compost mulch (compost/mulch). Sometimes every 2-4 weeks, depending on the weather, climate, season, etc.

Regarding part of your statement above, “, [if] the topsoil below is rich in mature organic matter like humus or mature compost already, there will not be any pH issues,” it may be a good idea to qualify that statement – your statement may be true for soils in Alabama, where pH is typically much lower than that of NE Texas. However, the Dallas/Ft. Worth Metroplex soils are generally very alkaline, and adding compost, even if it is fully finished, may do NOTHING to lower the pH, so the pH will remain too high for most landscape plants, thus prevent the growth you want and expect. To answer dtsager's original question, our customers have found that the only timely way to achieve a lower soil pH in the Metroplex area is to alter it with a compost that has a pH significantly lower than the native soil, AND the compost must have the appropriate buffer strength to swing the pH in the desired direction.

Importantly, you should also be certain that you’re buying from a reliable producer - many claim to offer pH-neutral compost, but our testing routinely shows that such compost is typically not pH neutral, or it is still in an active state of decomposition (i.e. not stable or suitable for plant growth). Again, we defer to our customers to make the most compelling case: http://www.SoilBuildingSystems.com/Inst ... Photos.php. The advice I can offer is to know your supplier and their track record. For more info on Metroplex soil issues, you can view answers to frequently asked questions at http://www.SoilBuildingSystems.com/FAQ.php, or write to Info@SoilBuildingSystems.com - we'll be happy to help you out.

Baron Ablon
Baron@SoilBuildingSystems.com

Hey Baron-
Good to hear from you on this forum. I ALWAYS enjoy hearing from the Captain but we need someone like you, right here in Dallas, that can help us at times. Thanks for your post.
Tony M

Tony,

Always happy to help. Keep up the good work!

Baron Ablon
Soil Building Systems, Inc.