April 8, 2000

Question: Under what circumstances would you recommend using milorganite on a floratam lawn?
- David Nahra

Answer: Milorganite is often used as a fertilizer that slowly releases nitrogen and iron. Nitrogen and iron are essential for good plant growth. The lack of either is expressed as a loss of green color in plant leaves. However, nitrogen, when applied in certain forms, promotes excessive leaf growth which becomes a source of food for lawn insects such as chinch bugs and caterpillars. Used at the wrong time, these fertilizers can add to your lawn problems. Milorganite, because of its slow release of nitrogen, is used frequently to assist in greening-up the lawn while reducing the chance of excessive top growth. 

Iron, another component of milorganite, is also often used to green-up floratam lawns in winter and summer without creating excessive top growth. Cool winter weather slows the ability of the grass to take up iron. This results in a loss of green color. In winter, iron application will help to maintain green color but, unlike nitrogen, iron will not promote excessive top growth that may be susceptible to a freeze. In summer, grass often grows so fast that it fails to pick up sufficient nitrogen and turns yellow. Applying iron in the summer is an alternate to a fertilizer high in soluble nitrogen. Although, both nitrogen and iron will green-up the grass, the latter provides a dark green color without the undesirable flush of growth that attracts chinch bugs and other insects.

Milorganite, or other slow release nitrogen and iron fertilizers, is best integrated in your total fertilizer program. Again, these slow release sources are best applied in the winter and summer to maintain a dark green cover without promoting excessive top growth.