Here is my translation of the first article Kiril linked for you guys. Reading just the translations may help some folks understand it easier. Traditionally people believed that if you add excessive N fertilizers, the plant would grow more, adding more soil organic matter to the soil. However, on a test site that has had half to almost 4 times more N atoms applied (as fertilizer) than removed (as crops) for 40 years we find that instead of increasing SOM, it has declined. Specifically the SOM found up to 18 inches down in the soil. Thus it appears that synthetic N promotes the decomposition of organic matter more than the buildup of it. The evidence for this is everywhere, including several "peer reviewed articles" even though in the past, no one has focused on this specific subject, or has "spoon fed" the information to the world. This is important to know/study because across the nation, especially with corn, we have been fertilizing in a way that reduces SOM for the last 50 years. To stop the problem, we should be fertilizing our corn fields based on how much N they need on a site to site basis. This will help reduce Nitrogen pollution, keep soil more fertile, and keep as much carbon sequestered in the soil as possible. Growing corn like we have, and now removing even more of the plant (the leaves and stock) for bio-fuel production, will increase the rate at which we lower our SOM levels. 50 years ago we thought we could increase both grain yields and soil quality by fertilizing synthetically and adding crop residue back into the ground. We thought the synthetic N would help humus develop because it would balance the C:N ratio (with the crop residue) and also provide N, which is part of many humic compounds. (Then a bunch of lingo describing the history of the testing plots, how they calculated how much Carbon was returned to the soil each year as crop residue, how they measured the current levels of SOM, etc. Basically information for the person who wants to make sure their calculations are credible.) If we were right 50 years ago, we should be able to easily tell it based on these test plots because the only things that were different between them were the fertilizer, amendment, and C inputs. It turns out we were wrong. Adding crop residue and fertilizer actually decreased the amount of organic C in the soil. Especially for the soil 6 to 18 inches down. (Then some more jargon how people usually didn't test the soil at those depths so they had to calculate and estimate how much SOM was in the soil at those depths.) Based on our data and calculations, there was no substantial increase in SOM over 50 years. This data is even more telling when we consider that because of the fertilizer, the plants have grown more, and thus we have added more crop residue back into the soil. But still, no increase in SOM. In fact a decrease was usually found. Add every pound of Carbon we put into the ground to how much Carbon was in the ground before the experiments, and we find that we have lost a significant amount of Carbon. This agrees with some published studies back in 1982 and 1984. But people didn't believe those studies. For the first ten years SOM increased on some specific plots. But even as we grew more corn in the same place, and thus added more plant residue to the soil, SOM levels declined after the first decade. Plots that had high amounts of fertilizer lost more SOM than plots that had regular amounts of fertilizer. Even though the Carbon input between the plots was the same. In plots that had extra fertilizer, SOM decline was even more apparent when crop rotation with another crop took place. This is important because most farmers currently rotate their crops. This practice may be depleting their SOM even faster. After some time, even adding Manure between the rotations doesn't help build SOM. These findings agree with publications made int 1994, 2006, 1197, 2001, and 2005. The evidence demonstrates that adding N to the soil increases the amount of microbes in the soil, but doesn't add to soil carbon sequestering. The difference between these two numbers demonstrates that N fertilizer enhances soil microbe activity. Especially in their ability to break down crop residue and soil organic matter. This has been understood clear back in the mid 1920's. And more recently in 1970, 1977, 1984, 1988, 1995, 2002, 2003, 2005) In other words, if you add N the microbes get happy and reproduce. They break down both plant residue and soil organic matter even faster now. (This is at the core of the salt debate) These findings are not popular because they are often interpreted to mean that farmers will make less money right now if they consider the information. (I would also say it isn't popular information amongst the organic crowd, at least in this forum, because it means that Synthetic N is good for microbes. At least short term. The sad part is, organic fertility is centered on SOM, and this should be at the core of investigation/discussion.) The quick dollar has promoted the 'grow for quantity' idea to expand rapidly worldwide. This idea calculates fertilization needs based on plant requirements. Basing fertilizing needs on soil requirements can help alleviate this problem without adversely affecting production numbers.