from the source above:
Effect of Nitrogen on Organic Matter

Excess nitrogen applications stimulate increased microbial activity that speeds organic matter decomposition. The extra nitrogen narrows the ratio of carbon to nitrogen in the soil. The native soil carbon to nitrogen ratio (C:N ratio) is around 12:1. At this ratio, populations of decay bacteria are kept at a stable level (20). When large amounts of inorganic nitrogen are added, the C:N ratio is reduced, which increases the populations of decay organisms and allows them to decompose more organic matter. While soil bacteria can efficiently use moderate applications of inorganic nitrogen accompanied by organic amendments (carbon), excess nitrogen causes bacteria populations to explode, decomposing existing organic matter at a rapid rate.

Excess nitrogen stimulates increased microbial activity that speeds organic matter decomposition.

Eventually, soil carbon content may be reduced to a level where the bacterial populations are on a starvation diet. With little carbon available, bacterial populations shrink and less free soil nitrogen is absorbed. Thereafter, applied nitrogen, rather than being cycled through microbial organisms and re-released to plants slowly over time, becomes subject to leaching. This can greatly reduce the efficiency of fertilization and lead to environmental problems.

To compensate for the fast decomposition of native soil organic matter, carbon should be added with nitrogen. Typical sources–such as green manures, animal manure and compost–serve this purpose well. Amendments containing too high a carbon to nitrogen ratio (25:1 or more) can tip the balance the other way, resulting in nitrogen tied up in an unavailable form. The soil organisms consume all the nitrogen in an effort to decompose the abundant carbon. The nitrogen is unavailable because it is tied up in the soil organisms themselves. As soon as one dies and decomposes, its nitrogen is consumed by another soil organism until the balance between carbon and nitrogen is achieved again.

xapabwa wrote:Morph, speaking of carbon additions - I still have lots of leaves. Can I mulch mow them and spread them over the lawn in the spring and summer or is this best to leave until fall?