Canola and spring wheat response to sulfur fertilizer, tillage, and landscape position

Canola (Brassica napus L.) is a relatively new rotational crop with spring wheat (Triticum aestivum L.) in North Dakota. Canola uses considerably higher levels of sulfur (S) than many of the traditionally grown crops in the area. Notill (NT) rotations have been promoted because of soil and water saving advantages over conventional tillage systems (CT), but little information exists on notill rotations with canola. Limited information also exists on S use by canola by landscape position.;Field experiments were conducted on a landscape over two growing seasons to study three soils, NT and CT, and four S fertilizer rate-sources with the specific objective of identifying specific differences in the S rate and sources among the soils and between tillage systems. Buse, Barnes, and Svea soil differ in their ability to mineralize enough sulfate-S to meet the S requirements of canola. Svea has increased potential to provide sulfate-S over Buse and Barnes soil and may require less additional S fertilizer for canola production.;Sulfur fertilizer additions increased canola production. The elemental (EL) S source was not as effective as ammonium sulfate (AS) in supplying S to the crop and was unable to maximize canola production when supplied the same season. A 22 kg S ha-1 AS application was almost as effective as 44 kg S ha-1 AS in obtaining maximum canola yield production. Canola plant N:S ratio of 7.2, sampled at flowering, was an acceptable method for determining whether soils provided S levels to obtain maximum yields.