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The Role of Sulfate Sulfur in Crop Production

What is the role of Sulfate Sulfur in Crop Production?

Sulfate Sulfur (SO4-S) has two major roles in production agriculture.

First Role: It’s the only form of the nutrient Sulfur that is available to the plant. As fertilizers have been scrubbed of the contaminant sulfur, it’s no longer a free component. It’s now seen as a minor-major nutrient, along with NPK. This nutrient is needed in proportion to Nitrogen in a 4:1 ratio. Its negative charge make it highly soluble so that it leaches much like Nitrogen.

Second role: The only way to reduce the Soil Cations* that are in excess, most notably Sodium, Magnesium and Potassium, and some rare cases, Calcium. These four cations exist in nature in the bi-carbonate form which is insoluble. SO4-S (Sulfate Sulfur) combines with the cation to make the SO4-S form of the offending cation.
Example: The cation takes Sodium carbonate and makes Sodium sulfate which is soluble and will leach from the soil profile.

*Cation exchange capacity (CEC) is the total capacity of a soil to hold exchangeable cations. CEC is an inherent soil characteristic and is difficult to alter significantly. It influences the soil’s ability to hold onto essential nutrients and provides a buffer against soil acidification.

SO4-S can be obtained from Gypsum ( CaSO4 ), Potassium Sulfate or any Sulfate fertilizer such as Zinc, Iron, Manganese, Copper, and Ammonium Sulfate.

Caution: For every 100# of SO4-S used, a corresponding amount of lime MUST be used to replace the Calcium lost.

Compost Solutions, Inc is always focusing on Living Soil and proper management of Soil nutrients.

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Gary Foster