Growth of soil microbial populations is limited by a lack of nitrogen. When large amounts of inorganic nitrogen are added, the C:N ratio is reduced. While soil microbes can efficiently use moderate applications of inorganic nitrogen accompanied by organic amendments (carbon), excess nitrogen results in decomposition at a rapid rate. Eventually, soil carbon content may be reduced to a level where microbial populations are on a starvation diet. With little carbon available, populations shrink, and less of the free soil nitrogen is absorbed. 

Excessive rates of applied nitrogen, rather than being cycled through microbial organisms and slowly released to plants, become subject to leaching. This can greatly reduce the efficiency of fertilization and lead to soil and water environmental problems. To minimize accelerated decomposition of soil organic matter, carbon such as that found in BioFlora Humega, should be added to all nitrogen fertilizer applications. Typical carbon sources such as humate soil amendments, green manures, animal manure, and compost help minimize the problem.