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How to Manage Pests

The UC Guide to Healthy Lawns

Water insoluble nitrogen (WIN)

The portion of slow-release nitrogen is listed on the fertilizer bag as water-insoluble nitrogen (WIN).

If no WIN is listed on the fertilizer label, assume that all of the nitrogen is water soluble or quickly available unless the nitrogen includes sulfur coated urea.

Sulfur-coated urea fertilizers provide slow-release nitrogen, but the fertilizer label does not list it as WIN. If the fertilizer contains sulfur-coated urea, include that portion as part of WIN when determining the percentage of total N that is slowly available.

Water-insoluble types of fertilizers release nitrogen over time. They are often applied at higher rates and less frequently than quick release formulas. The initial response of turf is slower than quick release types but these materials continue to provide nutrients over a period of 8 to 10 weeks or more. They will not burn the turf even if applied at high rates and are not prone to leaching.


Determine the amount of nitrogen that is water insoluble (WIN)

Statewide IPM Program, Agriculture and Natural Resources, University of California
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