Sulfur Management In the Northern Great Plains.

Sulfur (S) is essential for many growth functions in plants including: nitrogen metabolism, enzyme activity, and protein and oil synthesis.  Sulfur deficiency may affect both yield and quality of crops, the latter expressed as earlier and more uniform maturity and higher oil and protein levels as well as baking quality of bread.  Sulfur deficient environments in the northern Great Plains are most frequently associated with well-drained light textured soils as well as soils that were developed under forest vegetation and subsequently were opened to agriculture.  First step in S management is soil testing.  However, assessment of the S fertility status of soils in the area is particularly challenging due to the extremely high spatial or “in sample” variability of this nutrient that is associated with the presence of gypsum crystals in random patterns within fields and within the same sample. Second step is developing regional recommendations that are appropriate for the main crops in the area, i.e., small gain cereals, canola, pulses and forages. The correct balance of nutrients is particularly important for high S-using crops like canola and alfalfa grown on extremely S deficient soils. Third step is correction of the deficiency adhering to the 4R nutrient stewardship principle by selecting the right product to be applied at the right place, right time and right rate.  A discussion of an array of sulfate and elemental products and their applicability in the northern Great Plains environments will be discussed; placement of S product presents a number of challenges both in terms of seed safety and product efficiency; timing of application of S as it relates to various products as well as the feasibility of post emergence applications will be discussed along with the best fitted fertilizer rates for the circumstances.