Industrially produced N-fertilizer is essential to the production of cereals that supports current and projected human populations. We constructed a top-down global N budget for maize, rice, and wheat for a 50-year period (1961 to 2010). Cereals harvested a total of 1551 Tg of N, of which 48% was supplied through fertilizer-N and 4% came from net soil depletion. An estimated 48% (737 Tg) of crop N, equal to 29, 38, and 25 kg ha−1 yr−1 for maize, rice, and wheat, respectively, is contributed by sources other than fertilizer- or soil-N. Non-symbiotic N2 fixation appears to be the major source of this N, which is 370 Tg or 24% of total N in the crop, corresponding to 13, 22, and 13 kg ha−1 yr−1 for maize, rice, and wheat, respectively. Manure (217 Tg or 14%) and atmospheric deposition (96 Tg or 6%) are the other sources of N. Crop residues and seed contribute marginally. Our scaling-down approach to estimate the contribution of non-symbiotic N2 fixation is robust because it focuses on global quantities of N in sources and sinks that are easier to estimate, in contrast to estimating N losses per se, because losses are highly soil-, climate-, and crop-specific.
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机译:工业生产的氮肥对于谷物的生产至关重要,该谷物可支持当前和预期的人口。我们为玉米,水稻和小麦建立了一个自上而下的全球N预算,用于50年(1961年至2010年)。谷物总共收获了1551 Tg的氮,其中48%通过氮肥供应,而4%来自土壤净消耗。估计N的作物N达到48%(737 Tg),分别等于玉米,水稻和小麦的29、38和25 kg ha -1 sup> yr -1 sup>是由肥料或土壤氮以外的来源贡献的。非共生氮固定似乎是该氮的主要来源,为370 Tg,占作物总氮的24%,相当于13、22和13 andkg ha -1 sup> yr < sup> -1 sup>分别用于玉米,水稻和小麦。氮的其他来源是肥料(217 Tg或14%)和大气沉积物(96 Tg或6%)。作物残渣和种子的贡献很小。我们估算出非共生性N2固着作用的按比例缩小方法是稳健的,因为它着重于更容易估算的源和汇中的N总量,与估算N本身的损失相比,因为损失是高度土壤污染, ,气候和特定作物。
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