Wayne R. Kussow
Department of Soil Science
A USGA specification golf putting green, constructed in 1996 employing a commercial 80/20 root zone mix, did not respond satisfactorily in 1998 to a traditional fertility program. Soil analyses failed to pinpoint a reason for this, which raised the specter that the issue could be that of a low levels of microbial activity. Assays for dehydrogenase and FDA hydrolysis activities suggested that microbial activity was substantially lower thatn in an adjacent bentgrass fairway established on native soil.
The action taken in 1999 was to solicit from manufacturer’s and apply an array of products that claim ability to stimulate soil microbial activity. The purpose was two-fold:
1. To test product efficacy with regard to soil microbial activity; and
2. To determine if a significant relationship developed between putting green quality and root zone microbial activity
The following products were provide for testing:
Flexx Plus 3-0-20-“A complete micronutrient , biostimulant and beneficial bacteria package with dry, soluable yucca wetting agent.”
Synergy Blade 5-3-4- A liquid fertilizer derived from potassium nitrate, urea, phosphoric acid, potassium phosphate, and molasses.
Ocean Organics- An experimental liquid of unspecified composition.
Gro-Power Premium Green 5-3-1- A dry product containing ammonium phosphate, urea, potassium sulfate, oxides of Fe, Mn, Zn, and Mg, 15% humic acids derived from compos, and 1% yucca extract.
Nature Safe 8-3-5- A dry fertilizer derived from hydrolyzed feather meal, meat meal, bone meal, poultry meal, blood meal, fish meal, and langbeinite.
To the extent practical, all products were applied at the rates and frequencies recommended by the manufactures. The end result was, with exception of Synergy Blade, bi-weekly application at an N rate of 0.25 lb/M. Synergy Blade was applied monthly, but the schedule of 0.25 lb N/M/2 weeks was maintained. The control treatment was Lebanon’s Isotek 18-3-16, which was also used to adjust the other treatments to the bi-weekly 0.25 lb N/M rate if need be.
The materials were applied on June 21 to 6x10-foot plots in four randomized complete blocks. Prior to any application and at intervals of 2, 4, 8,16 weeks after the first application, five one-half inch diameter soil cores were randomly removed to a 6-inch depth from each plot for assessment of microbial activity. This was accomplished via assay for dehydrogenase (Tabatabai, 1994) and florescein diacetate (FDA) hydrolysis (Dick and Tabatabai, 1994). According to Dick (1997), dehydrogenase activity reflects the total oxidative activities of soil microflora important in oxidizig soil organic matter. Florescein diacetate hydrolysis reflects the hydrolytic capacities of proteases, lipases, and esterases, all of which are invloved in organic nitrogen transformations.
The plots were visually rated for putting green quality on 10 dates. Quality considerations were bentgrass color, uniformity, and the extent of development of localized dry spot. Root samples were collected in September to check for the presence of vesiculararbuscular mycorrhizae (VAM) according to the method of Sylvia (1994).
Dehydrogenase Activity (Table 1)
During the first 2 weeks after application, all the products induced substantial increase in dehydrogenase activity. As a result, all treatments had significantly greater activity than in the control (Isotek) treatment. The greatest increases occurred when Flexx Plus and Ocean Organics were applied, leaving these two treatments with significantly higher dehydrogenase activity than all others.
Between 2 and 4 weeks, the Flexx Plus and Nature Safe treatments registered declines in dehydrogenase activity, while activity increased in all other treatments. At 4 weeks, the Ocean Organics and Gro-Power treatments had dehydrogenase activities that were significantly greater than for an other treatment. All but Nature Safe had activities higher than the control.
Over the 4- to 8-week time frame, dehydrogenase activity declined in all but the Nature Safe and control (Isotek) treatments. The decrease in activity left Flexx Plus and Synergy Blade as being no different than the control, while Ocean Organics stood out in dehydrogenase activity.