Improving Declining Turf

"Milorganite is like a tonic!” says a highly experienced turfgrass consultant in Florida. This consultant recommends repeat topdressings with a 50:50 mix (by volume) of Milorganite 6-2-0 and sand to help recover weak areas on bermudagrass greens.

The Premise

In the late summer and early fall, bermudagrass greens in Florida often become weak, with thinning-out and development of poorly grassed areas. Presumably, this is a result of a combination of biotic and environmental stresses to the grass. These stresses include very hot, humid weather which favors disease development, reduced light intensity due to cloudiness and frequent afternoon rains , wet soils, insect and nematode pressure on roots, and close mowing which reduces photosynthetic area. Reserve carbohydrates, needed for growth and stress recovery, can be depleted rapidly due to high temperatures. Turf generally improves in response to clearer skies and cooler weather in the fall, but localized damaged areas can be slow to improve and fill in, with growth slowing due to the cooler and shorter days of autumn. While efforts should be made to identify and correct the stresses when possible, there also is a need to stimulate re-growth in the damage areas.

The Study

A study was conducted in the fall of 2005 on a ‘Tifdwarf’ research green at the UF/IFAS Ft. Lauderdale Research and Education Center to test the theory that Milorganite/sand topdressings will improve damaged turf on greens. Sufficient (1,330 ml) Greens Grade Milorganite/sand mix (50:50 by volume) to provide 1/16th inch of topdressing was applied to four replications of plots one yard square on September 8th, 16th and 23rd. The quartz sand met USGA specifications for a greens mix. Other plots in the experiment received either the same amount (665 ml) Milorganite or sand. Four replications of check plots were not topdressed. As a note, some superintendents will lightly spike or verticut the areas to be treated, and the topdressing may be brushed into the turf. These practices were not used in the study. Visual quality ratings for combined color and density were made on September 16, 30, and on November 4, 2005. Quality ratings, averaged over the three dates were subjected to the analysis of variance statistical procedure with means separated by the Duncan’s Multiple Range Test.

The Results

The Milorganite/sand topdressing treatment provided a higher average quality score than the untreated check. However, topdressing with Milorganite alone provided the highest quality score (Table 1). Topdressing with sand alone reduced the average quality score relative to the untreated check. It is concluded that topdressing with Milorganite improved grass quality. Sand should be included in the topdressing only if it is required to help level the surface or to dilute thatch or an organic layer.

Table 1: Effect of topdressing treatments on Tifdwarf bermudagrass quality ratings
Treatment Average Rating
Milorganite/sand 6.6B
Milorganite 7.6A
Sand 5.1D
Check 5.8C
Quality ratings are a 1 to 10 basis, with 10 best possible and 6 indicating minimally acceptable turf. Values in a column followed by the same letter are not statistically different at P < 0.05 by the Duncan’s Multiple Range Procedure.

Illustrating the Results on a Condominium Green

In a second study, a condominium golf green in Florida displayed severely stressed turf areas in September, 2006. Three approximately one foot square plots on the stressed areas were topdressed with Milorganite on October 7, 2006. Over the next few days, in an attempt to improve the weak areas, the green reportedly received applications of fungicide, insecticide, herbicide, and fertilization with a complete fertilizer and micronutrients. Nevertheless, the plots topdressed with Milorganite were strikingly improved in color and growth relative to the surrounding turf.


Milorganite Greens Grade, applied as a topdressing alone or in a mix with sand, is useful for restoring areas on golf greens that have stress damage from unfavorable late summer environmental conditions. Because Milorganite is very low in soluble salts, and the organically bound nitrogen releases slowly, Milorganite can be applied liberally without burning tender, stressed turf. Milorganite also provides phosphorus for encouraging new root growth, and abundant iron for developing deep green color.