How Reductions in Atmospheric Emissions May Result in a Return to Sulphur Fertilization in Ontario

Before 1880 “land plaster” (gypsum) was commonly applied to farm field as a source of sulphur for crop production in Southern Ontario. After this time the phosphorus fertilizer, single super phosphate, started to be used. In addition to the phosphorus in this fertilizer it also contains about 14% sulphur, which continued to meet the responses seen to added sulphur. This continued until the 1950’s when ammonium
phosphate largely replaced super phosphate as the primary form of phosphorus fertilizer used in Ontario. Ammonium phosphate contains no appreciable amount of sulphur, but studies at the time reported that sulphur fertilization was no longer required so this laws largely the end of sulpher fertilization in Ontario. By this time however, industrialization had resulted in considerable amount of sulphur deposition,
particularly in Southern Ontario and the North Eastern states, where deposition was in the rage of 30 – 50 kg sulphate ha-1 yr-1. This quantity more than met the crop requirement. In the last 15 – 20 years, improved environmental protection has been progressively reducing deposition levels to about 10 ha-1 yr-1. At this level, crop responses are occurring, in one of our studies alfalfa hay biomass was more than
doubled with applied sulphur; however, these responses are not consistent.
Therefore we need to develop tools that can identify when, where, and for which crops sulphur may be required in Ontario agriculture. This is a very exciting area as Ontario currently has no official sulphur recommendations so it will allow for the building of the entire recommendation system. This talk will review some of the research done to date in Ontario as well of some of the opportunities and challenges.

Alexander Hall Room 218 - All are welcome to attend.