化肥Fertilizer

植物需要的大量元素中，氮构成蛋白质和叶绿素，磷参与 ATP 和核酸合成、促进根系与开花结实，钾调节渗透压和酶活性、增强抗倒伏能力。李比希的“最小因子定律”指出，产量受供应最不足的那种营养限制。常见氮肥有尿素 CO(NH₂)₂（含 N 46%）、硝酸铵和硫酸铵；磷肥有过磷酸钙和磷酸铵；钾肥主要是氯化钾和硫酸钾。

Among the major nutrients, nitrogen builds proteins and chlorophyll, phosphorus goes into ATP and nucleic acids and promotes roots, flowering and fruit, and potassium regulates osmotic pressure and enzyme activity and strengthens stems. Liebig's law of the minimum says yield is limited by the scarcest nutrient. Common nitrogen fertilisers are urea, CO(NH₂)₂ (46% N), ammonium nitrate and ammonium sulfate; phosphates include superphosphate and ammonium phosphates; potash is mainly potassium chloride and sulfate.

1840 年李比希出版《化学在农业和生理学上的应用》，奠定矿质营养理论。1842 年劳斯在英国用硫酸处理磷矿生产过磷酸钙，并建立洛桑试验站。19 世纪依靠智利硝石和鸟粪供氮，1913 年哈伯-博施法使合成氨大规模生产，化肥成为二十世纪粮食增产的关键因素。

Liebig's 1840 Organic Chemistry in its Application to Agriculture and Physiology laid the foundation of mineral nutrition. In 1842 Lawes in England began making superphosphate by treating phosphate rock with sulfuric acid and founded the Rothamsted experimental station. Nineteenth-century nitrogen came from Chilean saltpetre and guano, until the Haber–Bosch process of 1913 enabled mass ammonia production, making fertilisers a key driver of twentieth-century food production.

过量施用会导致土壤酸化、板结，氮磷流失造成水体富营养化，氮肥转化还产生强温室气体 N₂O。铵态氮肥不能与草木灰等碱性物质混用，否则会放出 NH₃ 损失肥效。测土配方施肥、缓控释肥和硝化抑制剂可提高利用率。

Overuse acidifies and compacts soil, nitrogen and phosphorus runoff causes eutrophication, and nitrogen transformations release N₂O, a potent greenhouse gas. Ammonium fertilisers should not be mixed with alkaline materials such as wood ash, or NH₃ escapes and nitrogen is lost. Soil-test-based dosing, slow-release fertilisers and nitrification inhibitors raise efficiency.