TY - JOUR T1 - The nitrogen dilemma: Food or the environment JF - Journal of Soil and Water Conservation SP - 124A LP - 128A DO - 10.2489/jswc.72.6.124A VL - 72 IS - 6 AU - B.A. Stewart AU - Rattan Lal Y1 - 2017/11/01 UR - http://www.jswconline.org/content/72/6/124A.abstract N2 - Nitrogen (N) is the most important essential element for crop production because it is required in large amounts and is nearly always the first nutrient that becomes limiting after an ecosystem is converted to cropland. Cereal grains provide about 50% of the world's calories, and their production has become largely dependent on the use of synthetic N fertilizer. However, fertilizer N not used by plants can degrade the environment and negatively impact both people and ecosystems. In addition, efficient use of N fertilizer generally requires phosphorus (P) fertilizer which is made from rock phosphate derived from mines. Therefore, huge amounts of N and P from outside sources are being added to the environment each successive year leading to additional environmental concerns.RISE IN NITROGEN FERTILIZER USE By the early 1800s, it was becoming increasingly clear that there was a great need for N fertilizers. Europeans began importing guano (solidified bird excrement) and sodium nitrate (NaNO3) from South America (Smil 2001), but it became apparent that supplies of these N sources would be insufficient. Coal contains between 1% and 1.6% N, derived from the decomposition of proteins that were present in the biomass that was eventually transformed by pressure and heat… ER -