Lawn fertilizer often contains quick release nitrogen (water soluble nitrogen) and slow-release nitrogen (water insoluble nitrogen). We suggest you consider using a fertilizer that contains at least 50% “slow release” nitrogen which is less likely to leach and is a good choice for very sandy soils.

The fertilizer analysis of this bag of No-Name Lawn Fertilizer (box, right) is 30-5-10. The analysis printed on the bag indicates the % nitrogen (N), available phosphorus (P) and potash (K) that is contained in the bag. Read the label to determine how much nitrogen is quickly available and how much is slowly available.

Look on the label for the language “slowly available nitrogen” or “water insoluble nitrogen” (WIN), or something similar. In this example the WIN is 15%. That means that half of the total nitrogen is slow release.

Divide the amount indicated as water insoluble nitrogen (WIN) by the first number of the three hyphenated numbers (nitrogen).

This fertilizer has ½ water insoluble nitrogen which is slowly available to the grass and less likely to leach if heavy rains occur shortly after application.

To lower the risk of nitrogen leaching into our groundwater, do not apply more than ½ lb of water soluble nitrogen per 1,000 sq ft per application. After applying the fertilizer, water the lawn lightly with ¼ inch of water or less to wash the fertilizer into the soil so the grass can take up the nutrients.

Remember not to fertilize if a heavy rainfall is expected within 2 days of planned fertilizer application.

For application tips, see Simple Spreader Calibration and Simple Spreader Calibration Worksheet and Example Worksheet