Comparison of Ammonium Sulfate With Other Nitrogen and Sulfur Fertilizers in Increasing Crop Production and Minimizing Environmental Impact: A Review

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 NH3 and nitrite to plants in alkaline soils; (ii) no N loss via NH3 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 CO2 emission to greenhouse gases; (vi) a potential to use AS to reduce NH3 volatilization from urea and enhance N efficiency of urea; (vii) more acidic root rhizosphere via preference absorption of NH4-N of AS to NO3-N of AN that may increase availability of soil P, applied phosphate rock, and micronutrients; (viii) less NO3-N leaching from AS than AN can increase N efficiency and reduce NO3-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 N2O). 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 SO4-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.