Ammonium sulfate (AS) provides critical plant nitrogen (N) and sulfur (S) nutrients. Compared with other N fertilizers, such as urea and ammonium nitrate (AN), AS may have some potential agronomic and environmental benefits. These are (i) no potential toxicity of aqueous NH 3 and nitrite to plants in alkaline soils; (ii) no N loss via NH 3 volatilization when surface applied to acid or neutral soils; (iii) a better N source for saline soils by decreasing the negative specific effects of NaCl on plant growth and for saline sodic calcareous soils by improving soil structure; (iv) positive effects of soil acidification on increasing availability of soil phosphorus (P) and applied phosphate rock and soil and applied micronutrients; (v) no contribution of CO 2 emission to greenhouse gases; (vi) a potential to use AS to reduce NH 3 volatilization from urea and enhance N efficiency of urea; (vii) more acidic root rhizosphere via preference absorption of NH 4 -N of AS to NO 3 -N of AN that may increase availability of soil P, applied phosphate rock, and micronutrients; (viii) less NO 3 -N leaching from AS than AN can increase N efficiency and reduce NO 3 -N pollution in groundwater and eventually drinking water; and (ix) less denitrification with AS than AN that may increase N efficiency and minimize greenhouse gases (NO and N 2 O). Ammonium sulfate is more effective than granulated elemental S (ES) or ES-enriched NP fertilizers to provide S nutrient because AS is water soluble, whereas ES requires S oxidation to SO 4 -S. The possible negative effects of AS compared with other N and S fertilizers are high soil acidification may require more liming and a higher cost per unit of N applied. However, the N cost of AS includes free S nutrient.

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