Evaluation of biosolids‐enriched ammonium sulfate vs. ammonium sulfate in soils and for plant growth

Nitrogen (N) and sulfur (S) are essential nutrients for optimum plant growth. A commercial‐grade biosolid‐enriched ammonium sulfate (Bio/AMS) was evaluated and compared with a conventional, commercial‐grade ammonium sulfate (AMS) to investigate the release patterns of N and S in soils. The laboratory‐based studies included (a) characterization of fertilizer sources, (b) soil leaching columns with 0.01% citric acid in an acid soil, (c) soil incubation followed by 1 M KCl extraction in a neutral soil, and (d) NH3 volatilization measurements in an alkaline soil. With one exception, the results showed no significant difference in the amount or the rate of N or S released from each between the two products in all the studies. In that one exception, the Bio/AMS leached significantly less N after 56 d, but not before 14 d, than the conventional AMS application. In greenhouse‐based evaluations, the Bio/AMS and AMS performed comparably at providing S nutrient to the biomass yield and S uptake by canola (Brassica napus L.) at maturity in neutral and alkaline soils. The studies also showed no significant N uptake differences between Bio/AMS and AMS by wheat (Triticum aestivum L.) biomass at maturity in acid and neutral soils. The results from these laboratory and greenhouse studies demonstrated that the Bio/AMS product is a simple physical mixture of biosolids with AMS.