Other factors contributing to the frequency of sulfur deficiency symptoms are the increasing use of no-till or minimum-till practices that increase surface residue, the lack of tillage that mixes shallow soil layers with nutrients deeper in the soil profile, and marginal to low soil pH.

The increasing surface residue and reduced-tillage means soil temperatures are cooler in the shallow seed zone resulting in slower root growth during the switch between the radicle and seminal root systems and cooler temperatures reduce the efficiency at which roots take up nutrients.

The lack of soil mixing means the differential in sulfur concentrations between the shallow and deeper soil profile becomes greater over time with less sulfur in the surface layer and more in the deeper profile.

Therefore, while the soil test may show adequate or high levels of sulfur, the upper 2-4 inch layer may have much lower concentrations.

Low soil pH results in less available sulfur (as well as other needed plant nutrients), stunting of needed root development, and generally enhances the deficiency symptoms relative to fields with adequate pH levels, Crozier says.

It’s likely that sulfur emission standards are likely to get even tighter in the future, making atmospheric sulfur even harder to come by. For growers there are short and long-term options for correcting sulfur deficiencies Crozier says.

For growers who document sulfur deficiency damage on a crop, some sulfur should be applied.

How much to apply and in what form varies greatly, depending on the severity of the problem and myriad farm production practice differences. The point is, if there is damage to the crop, sulfur needs to be applied, Crozier adds.

In some cases soil tests may show adequate sulfur, but plant damage still occurs. Crozier says even though the soil index shows adequate sulfur, in some cases the plant is not able to develop enough root volume to reach the deeper sulfur concentrations.

Long-term solutions should be based around yearly soil samples and fertilizing to achieve proper sulfur index levels.

“On low CEC, sandy soils it is becoming apparent that yearly soil tests are needed to help monitor rapidly changing nutrient conditions associated with leaching of soluble nutrients,” Crozier says.

In situations where the grower is using no-till practices it is a good idea to have a soil test done on the top 2-4 inch layer separately from the 8-inch core sample. This way a shallow deficiency can be found and corrected.

Growers who leave more surface residue, who plant early in the season when soil temperatures are cooler, or who have extremely sandy soils should consider adding sulfur in their pop-up fertilizer in a 2 X 2 band or at least applying some sulfur pre-plant, he adds.

rroberson@farmpress.com