Beware of the N-bomb
There are good, and frightening, reasons to closely follow the changes in the nitrogen cycle. We should not be surprised if the effects and costs of disturbing it turn out to be as dramatic as those for the carbon cycle. In addition, greenhouse gas emissions from nitrogen fertilizers are around 3% of global emissions, but they are not visible in greenhouse gas inventories. The abolition or drastic reduction in the use of chemical fertilizers is a pre-condition for a sustainable food system.
In farming, the availability of nutrients, particularly of nitrogen, potash and phosphorus – mostly referred to by their chemical symbols N, P and K – is a major limiting factor. All traditional farming systems have had some strategy for replacing nutrients in the soil. One is to rest the soil and allow a natural re-charge and release of nutrients from the soil and through atmospheric decomposition. Crop rotations with leguminous crops can fix nitrogen from the air and the nutritional demands of the various crops can complement each other. Phosphorous, from deeper layers or bound in the soil, can be ‘mined’ by some crops making it available to others. Nutrients can also come from irrigation water (especially sediments in flood waters), animal manure, human waste, plants, grass and other residues, a plethora of natural organic fertilizers. Farmers have used oil-cakes, feathers, leathers, bone, sea weed and fish as fertilizers. There are even reports that human remains from battlefields and ossuaries have been used as fertilizers. Yet all these methods have some limitations, and in most cases they require a lot of work or other efforts.
…click on the above link to read the rest of the article…
