Nitrites come from a variety of sources of nitrate within the agricultural environment, including high-nitrate fertilizers. Nitrates are taken into plant tissues and used in the synthesis of proteins, but only at a relatively-slow rate compared to what is often present. For instance, Ag Extension recommendations often specify the application of an entire season’s (highly-soluble) nitrogen/nitrate needs at one time. This virtually ensures not only uptake of more nitrate than can be metabolized by a plant at once, but also leaching of further quantities of highly-soluble nitrates into ground water, a common problem in agricultural areas, as well as under dairies and feedlots due to leaching of stored manures. Regulatory agencies in most localities now require covering of manure piles to prevent leaching, but urines are still ignored, as well as nitrate leaching from agricultural applications.
Nitrates and nitrites are metabolized in the human stomach into nitrosamines, which are carcinogenic and corrosive to the system. Soule and Piper (Farming in Natures Image, 1992) report that “At concentrations of forty-five parts per million, [nitrates from fertilizers] can cause fatal methemoglobinemia disease, or “blue baby syndrome” in infants receiving formula made from contaminated water… ON THE AVERAGE, ABOUT 50 PERCENT OF THE FERTILIZER APPLIED IN THE UNITED STATES IS NOT USED BY CROPS” [my caps]. Nitrates are only extremely-slowly degraded, and so very persistent, once they have reached groundwater, due to the absence of oxygen and bacterial action. Further problems with surface waters are produced concurrent with the groundwater problems, of course, including suffocation of fish caused by depletion of dissolved oxygen by nitrate-jazzed bacterial and algal metabolisms gorged on nitrates washed into creeks, rivers and lakes.
The safest way to apply nitrates/nitrogen/manures/ammonia/etc is by incorporation into a mulch with active bacterial and fungal populations, a little at a time, or by using leguminous green manures, which release their nitrogen slowly over a season (40% if mowed, to 60% if tilled in, during the first year, the total over about 3 years). Greenhouse operators, not known for savvy in avoiding chemical use, have nonetheless acknowledged, for reasons having purely to do with productivity and costs, that nitrogen should be applied gradually, in tiny doses, evenly throughout the growing season for maximum effect.
Nutritionists recommend holding back nitrogenous fertilizers for several weeks prior to harvesting leafy greens for human or animal consumption, to give the plants time to metabolize nitrogen taken into their tissues in excess of what can be quickly used. This is especially important for young children.
Reproduced here with the permission of Jack Rowe. This article was originally a post to the Permaculture MG email