TRPA Stormwater Management Program
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Multi-Family & Commercial Property Owners
Apply fertilizers sparingly and with great care
If you have turf on your property and want to protect Lake Tahoe’s water quality, one of the most important things you can do is avoid over-fertilizing your lawn. It’s vitally important to prevent plant fertilizers from washing off the property or infiltrating to groundwater. When these fertilizers enter the lake, they become food for unsightly algae which fouls near shore rocks and reduces water clarity.
The goal of lawn fertilization is to stimulate root growth, which is essential for controlling erosion and reducing weed growth. Residents and businesses are urged to apply fertilizers to turf only twice each year, in spring and late summer. Property owners who hire lawn-maintenance firms should direct the foreman to fertilize using the recommendations outlined below.
Pay attention to the timing of your fertilizer application. In the spring, apply lawn fertilizer only after the snowpack has melted. On shady high elevation or north-facing sites, aim for a June application in most years. On warmer south-facing sites, or after a warm spring, fertilize in late April or May. Apply fertilizer again in late August in higher cooler locations or the first half of September in warmer sites near lake level. This promotes a vigorous, healthy root system and a hardy crown without encouraging shoot growth.
The Tahoe Regional Planning Agency (TRPA) recommends the use of phosphorus-free fertilizer except when establishing new turf from seed. Tahoe soils have adequate phosphorus for turf for many years. The label on a fertilizer bag shows the percentage of the primary plant nutrients as a string of three numbers. These numbers indicate the percent by weight of nitrogen (N), phosphorus (P) and potassium (K). Look for a fertilizer in which the middle number is 0.
It is possible that after several years of fertilization with no phosphorus, the soil could become deficient. If turf grass blades turn purple, reddish-brown or dark green, and show slowed growth, the soil may be deficient in phosphorus. A simple N-P-K soil test from a commercial soil testing lab can tell if phosphorus is needed. A fertilizer with a phosphorus content of less than five percent may be applied in this case. Be wary about following fertilizer application rate recommendations from soil testing labs. Sometimes a lab will recommend rates higher than those appropriate for Lake Tahoe.
For the spring and fall applications of fertilizer, use only about one-half to three-quarters of the recommended fertilization rate found on the label. Be sure to water slowly following the application using the cycle and soak method (turning the water on and off, allowing the water to soak in).
Fertilizers are always represented by a formula consisting of three numbers in the same order: Nitrogen (N) is the first number, Phosphorus (P) is in the middle, and Potassium (K) is the last number. Look for a “zero” in the middle for phosphorus-free fertilizer blends.
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