Turf Fertilizers and Weed Control: The Benefits of Controlled-Release

Effective weed management begins with proper turf nutrition. The availability of nutrients – particularly nitrogen – can significantly influence the germination, growth, and competitiveness of both turfgrass and weeds.

Excessive applications of readily available nitrogen often favor opportunistic weed species and undesirable grasses. By contrast, controlled-release nitrogen fertilizers provide a gradual nutrient supply that better matches turfgrass demand, helping maintain a dense turf stand while reducing conditions that encourage weed development.

Seasonal Effects of Nitrogen Availability

Late Fall

Applications of readily available nitrogen late in the season may stimulate the germination and establishment of winter annual grasses, particularly Poa annua and Poa trivialis.
Once established, these species can become difficult to control and may reduce turf quality and uniformity.

Late Winter

During late winter and early spring, Poa annua often responds more aggressively to nitrogen than many desirable cool-season turf species.
Excessive nitrogen availability during this period can encourage its germination, growth, and spread.
Careful nitrogen management is therefore essential to limit weed pressure while supporting healthy turf development.

Late Spring

High levels of readily available nitrogen can also stimulate the germination and growth of summer annual grasses, including Setaria, Digitaria, Echinochloa, Eleusine, and Cynodon species.
Controlled nutrient release helps reduce nutrient surpluses that favor these competitive weed

Proven Results

The graph below presents Poa annua density ratings measured in two turf species at the end of March under different nitrogen fertilization programs.

The results demonstrate that controlled-release nitrogen sources can help reduce weed pressure by limiting excessive nitrogen availability while maintaining healthy turf growth and quality.

Delivering controlled-release nitrogen, Multigreen™ reduced Poa annua density compared with readily available nitrogen sources, demonstrating the value of controlled nutrient release as part of an integrated weed management strategy.

The Advantage of Controlled-Release Nitrogen

Supports steady turf growth without excessive flushes of vegetative development.
Helps maintain dense, competitive turfgrass stands.
Reduces conditions that favor the establishment of Poa annua and other weed species.
Contributes to more efficient nitrogen use and improved turf management.