Jashandeep Kaur, NDSU Department of Soil Science
Amitava Chatterjee, NDSU Department of Soil Science

Sulfur (S) is considered the fourth major nutrient for optimum plant growth and development. Unlike other major nutrients, researchers have not studied S extensively mainly because it was highly available from several sources like industrial emissions, fertilizers and pesticides, but several S deficiency incidences have been recorded in the Northern Great Plains. The major reasons are: declines in atmospheric S deposition, use of high analysis fertilizers with no or low S, and continual S removal by crops like corn, canola and alfalfa. Fertilizers like ammonium sulfate and ammonium thiosulfate have the potential to overcome S deficiency. However, the lack of accurate soil testing methods restricts the ability to determine the soil S levels and the amount of fertilizer S required.

In recent times, S deficiency in corn has been recorded at many sites. This results in lower corn grain yield and chlorosis of new leaves. Generally, a corn crop with 180 bushels/acre yield removes 16 lbs of S/acre. Previous research across North Dakota recommended to apply 10 lbs of SO42-/acre of ammonium sulfate for corn in low organic matter coarse textured soils. Our study aims to revisit this recommendation by determining the corn response to various S treatments. In addition, we will evaluate the relationship between plant S uptake and yield at critical crop stages.

Our experiment was planned at five sites: Absaraka, Ada, Downer, Gardner and Walcott for the 2016 growing season. Five S treatments (0, 10, 20, 30 and 40 lb SO42- S/ acre) were applied using ammonium sulfate in randomized complete block design with four replications. Our objectives were 1) to evaluate corn response to five S application rates and 2) to determine relationship between corn S uptake and yield under different soil types.
Our results showed that corn response to S was observed at one site (Downer) out of five sites. Significant increase in yield at Downer with fertilizer application might be due to low organic matter and sandy loam soils. Sandy soils have less capacity to retain nutrients and at more risk for S deficiency due to its high leaching potential. In addition, the soil organic matter was less at this site (3%) compared to other four sites. Thus, the mineralization of soil organic matter could not provide enough S to meet plant needs at this site and corn showed response to the applied S fertilizer whereas enough S was available from soil organic matter at other sites and no response was observed to applied S. In addition, no relationship was noticed between corn yield and plant S content. We are conducting this experiment in 2017 to validate our findings.