Sulfate fertilization of ryegrass soil columns negatively affects microbial communities and nematodes but improves plant sulfur supply and growth

Recent reductions in atmospheric pollution have seen increased use of sulfate fertilizers to compensate for plant sulfur (S) limitation. However, this may affect soil microbes and micro-fauna involved in natural S mobilization. Here, grassland soil columns with Lolium perenne were fertilized with 0, 5, 10 and 20 kg/ha (control/quarter/half/full) inorganic sulfate-S alongside a full complement of other nutrients. In the half and full treatments, significantly higher amounts of sulfate were present in soil solution. Destructive sampling revealed a significant decrease (P<0.05) in arylsulfatase activity, bacterial-feeding nematodes, mycorrhizal colonization rates, and significant shifts the bacterial, fungal and AM community structures in the half and full columns compared to the control. Half and full S treatments had significantly higher grass dry matter yield and uptake of S, N, K, Ca and Mg compared to the control. While the overall bacterial diversity was reduced in the full S treatment, the abundance and asfA gene copies of Variovorax, Burkholderia and Polaromonas, and diversity of bacterial genes involved in S cycling (ssuD and atsA) were not affected by one-time sulfate fertilization. On balance, sulfate fertilization benefits to the plants outweighed the negative effects to the soil biota after a single application.