Transformations and Fate of Seed-Placed Sulfur Fertilizers in Saskatchewan Soils Jeff Schoenau and Derek Peak, University of Saskatchewan, Saskatoon SK, SS. Mahli, Agriculture and Agri-Food Canada, Melfort SK Project Code: CARP SCDC 2012-15 Final Report: February 2016 Sulfur (S) fertilizers have become an important part of the fertilizer mix for Saskatchewan growers, not only for canola, but also for pulse and cereal crops. The overall objective of this study was to evaluate the effectiveness of different fertilizer forms as sources of plant available S to crops. Field studies in three different soil zones showed that canola was the most responsive to S, and that most of the S uptake occurred over the period from one to four weeks after seeding and fertilizing. In addition, the Canadian Light Source synchrotron was used for the first time to track the fate of fertilizer S and P together in soils and shed light on the kinds of fertilizer reaction products formed and their availability to plants. Sulfur (S) fertilizers have become an important part of the fertilizer mix for Saskatchewan growers, not only for canola and other Brassicae crops, but also for pulse and cereal crops. The form of sulfur (S) fertilizer can influence both its behavior and crop response. It is important to understand the fate of the S fertilizer applied when attempting to predict the relative performance of different sulfur fertilizers, for different crops, under varying application conditions. The overall objective of this study was to evaluate the effectiveness of different fertilizer forms as sources of plant available S to crops. Three soils were chosen for the study to provide a contrast in soil properties, and to represent the different agricultural regions of Saskatchewan. The specific objectives of the study were to investigate the effects of five different S fertilizer forms applied alone and in combination with monammonium fertilizer (MAP) in these contrasting soils under controlled environment conditions and in the field, The study looked at the effects on supply rates and concentrations of plant available sulfate and phosphate in the seed-row following fertilizer application, crop (canola, pea, wheat) uptake of S and P, and yield. Field studies were conducted in 2013 and 2014 at three Saskatchewan sites: Central Butte (Brown), Star City (Gray) and Melfort (Black), all marginally deficient in sulfur, along with a growth chamber study. In the studies, researchers evaluated five sulfur fertilizer forms (ammonium-sulfate, ammonium-thiosulfate, gypsum, potassium-sulfate and elemental-sulfur) applied in the seed-row with wheat, canola and yellow peas at 20 kg/ha S alone and in combination with MAP at 20 kg/ha P2O5. The fate of the fertilizer was evaluated by measuring soil available sulfate and phosphate in the seed-row, crop S and P uptake, and grain yield. Another goal of the study was to develop and employ new