Ag Instructor Vic Martin: Sulfur and Chloride for Wheat

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Great Bend Tribune
Published March 14, 2021

As of this past Tuesday, the Drought Monitor is showing dry conditions/drought creeping southeast. Almost two-thirds of the state ranges from Abnormally Dry to Extreme Drought in the northwest. Barton County is still abnormally dry and that is creeping into Stafford County. The rains at the end of the last few days are well-timed to help not only for the wheat but for prairie grasses and the upcoming spring planting season. The six to ten-day outlook (March 17 to 24) indicates a good chance of below-normal temperatures and precipitation. The eight to fourteen-day outlook (March 19 to March 25) indicates normal temperatures and about normal precipitation. If we have received the promised approximately two inches of precipitation this weekend, it’s good weather to prepare for spring planting and help the wheat along.

Wheat in the area is greening up and it’s time to make sure it’s positioned for optimal yields. In addition to the normal nitrogen and herbicide consideration, let’s take a quick look at two nutrients worth consideration, especially on our coarser textures, sandier soils, but for all producers.

First up is (S) sulfur, a macronutrient. Briefly, Sulfur equals protein in grain as all plant proteins have sulfur-containing amino acids. Sulfur deficiencies show up as an overall yellowing of the plant, on younger leaves first, as opposed to older leaves first (potassium and nitrogen). Deficiencies are more likely on no-till fields, high yield fields, and on sandier soils low in organic matter. Sulfate sulfur is an anion and like nitrates is subject to leaching so if you want to take a soil test, and it should be done now if you are concerned, it should be to 24 inches. Many experienced producers know they need sulfur and don’t bother with a soil test. The bright side is that it can be easily corrected and won’t cost a fortune. And you can use liquid or dry formulation, depending on what is available.

Dry sulfur fertilizers for top dressing include: Ammonium Sulfate (21-0—24S); Calcium Sulfate (Gypsum) which is usually around 19% sulfur; products like K-Mag, and there may be other sources depending on your supplier. There can all be surface applied and the sulfate is readily available. Liquid sources include Ammonium thiosulfate (12-0-0-26S) and Potassium Thiosulfate (0-0-25-17S). Again the sulfur should be readily plant available. And these can be applied in combination with nitrogen.

The second is (Cl) chloride, a micronutrient. Chloride is highly mobile in the soil as an anion and has been determined as important in disease suppression and overall plant health, especially in grass crops like wheat. We see deficiencies as we haven’t used much Potash (KCl) as many Kansas soils had/have high potassium levels. A Chloride deficiency is most likely on sandier soils and where potassium fertilization hasn’t been necessary. A test to 24 inches is necessary if you are concerned. Again as with sulfur, many producers know they need chloride and don’t worry about a soil test. The most common source of readily available chloride is Potash. One caveat, wheat varieties vary in their response to chloride but those that do can see up to a twenty percent yield increase from this inexpensive application.