AdvanSix’s agronomy experts are available to answer your questions about how to get the most out of your ammonium sulfate investment. Mercedes Gearhart has overseen agronomic research at AdvanSix for more than 20 years, and has a wealth of knowledge about fertilizer use efficiency and improving crop yields. Check out the questions asked below or ask your own question.

I'm looking for a product to lower soil pH for hydrangeas. Would Sulf-N® work? What should the application rate be?


Optimum pH for the typically-preferred blue hydrangeas is between 4.5 and 5.5. Sulf-N® ammonium sulfate can indeed help lower soil pH.

As for the rate of application, it will depend on the pH and the buffer capacity of the soil. If you submit a soil sample to a soil testing lab, you will be provided with a specific rate recommendation for your soil. Generally speaking, the higher the soil pH, the higher the organic matter level and the heavier the texture, the more Sulf-N ammonium sulfate it will take to lower the soil pH. Depending on the situation, it may make sense to split-apply the total amount of product over several seasons, gradually achieving the perfect blue color.

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