INTRODUCTION

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

METHODS

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).

RESULTS

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.

Dehydrogenase activity increased in all but the Nature Safe treatment over the 8- to 16- week period. At 16 week, the Ocean Organics treatment exhibited the highest dehydrogenase activity. Due to the decline in activity in the Nature Safe treatment, it had dehydrogenase activity that was less than the control.

Over the entire 16-week period, means of dehydrogenase activity showed that all treatments had positive effects in comparison to the control. The treatment with the greatest influence was Ocean Organics. Nature Safe had the least effect on dehydrogenase activity and, when viewed with regard to the mean increase in activity over the initially present, did not have a significant influence. The Flexx Plus, Synergy Blade, and Gro-Power treatments clearly showed positive and significant effects on dehydrogenase activity.

FDA Hydrolysis Activity (Table 2)

Treatment effects on FDA hydrolysis activity were notably less than for dehydrogenase activity even though initial activity was roughly one-third that for a nearby native soil bentgrass fairway. There were no significant changes in soil FDA hydrolysis activity during the first 2 weeks after product application. Increases occurred in the second 2-week period, but they are too small to result in significantly higher levels than in the control treatment.

All treatments, including the control, induced increases in FDA hydrolysis activity during the 8- to 16- week time frame. At 16 weeks, the Flexx Plus and Synergy Blade treatments had significantly greater FDA hydrolysis activity than the control and Flexx Plus was significantly better than Synergy Blade. The FDA hydrolysis activities for the Ocean Organics, Gro-Power, and Nature Safe treatments were no different than for the control.

Given the minimal effects of the various products on FDA hydrolysis activity, it is not surprising that the 16-week means showed no significant treatment effects. Among the products tested, Flexx Plus had the greatest influence on FDA hydrolysis activity. When examined from the perspective of mean FDA hydrolysis activity versus the initial activity, only Flexx Plus, Ocean Organics, and Gro-Power had significant influences.

Putting Green Quality (Table 3)

A quality rating of 6.0 is considered to be minimally acceptable on a first-class golf course. Two weeks after product application, all but Nature Safe and Isotek provided this
Level of putting green quality. However, only Gro-Power produced a quality rating significantly better than the control (Isotek) treatment.

Table 3. Treatment effects on putting green quality.
	Quality rating
Treatment			0 wk	2 wk	4 wk	8 wk	16 wk	Mean*
Flexx Plus			5.52	6.20	6.78	6.25	6.62	6.74
Synergy Blade			5.48	6.05	6.70	6.20	6.65	6.62
Ocean Organics			5.50	6.38	7.38	6.65	6.95	7.13
Gro-Power 5-3-1			5.52	6.48	7.32	7.00	7.02	7.03
Nature Safe 8-3-5			5.50	5.80	6.18	5.70	6.30	6.16
Isotek 18-3-16			5.45	5.98	6.18	5.98	6.05	6.18
Duncan's LSD (p=0.05)			NS	0.44	0.33	0.39	0.86	0.25
* Number of 10 ratings ** NS, no significance

As air temperature declined, putting green quality ratings increased during the 8- to 16- week period. All treatments, with exception of Nature Safe, were then providing significant improvements in putting green quality in comparison to the control.

Means of the 10 quality rating taken over the 16-week after initiation of the treatments showed that all but Nature Safe generally induced significant quality improvements. The Ocean Organics product and Gro-Power were outstanding regarding their influences on putting green quality. Both were significantly better than Flexx Plus, Synergy Blade, and Nature Safe.

Putting Green Quality vs. Enzyme Activity

A key question in this preliminary study was whether or not a relationship exists between putting green quality and microbial activity as gauged by enzyme activity. The standard technique of regressing putting green quality on enzyme activity was employed to address this question.

As shown in Figure 1, there was no meaningful relationship between FDA hydrolysis activity and putting green quality. Perhaps this was to be expected given the rather limited treatments effects seen regarding FDA hydrolysis activity.

In contrast, there was a highly significant relationship between dehydrogenase activity and putting green quality (Figure 2). This observation strongly indicates that further investigation of the relationship of enzyme activity to putting green quality could prove to be a very fruitful line of research. A logical next step is to explore the causes for this relationship and to determine to what level of dehydrogenase activity further improvements in putting green quality will be manifested. As a starting point, bentgrass clippings collected from the plots on week 8 will be analyzed to test the hypothesis that the effect of dehydrogenase activity is nutritional in nature.

As of this moment, the roots collected in September for examination for the presence of vesicular-arbuscular mycorrhizae have been clarified and stained in preparation for microscopic examination. This will be done over the next 2 to 3 weeks, and any obvious treatment influences will be reported at a later date.

CONCLUSIONS

The results of this exploratory study serve as preliminary evidence that the products tested can significantly alter the dehydrogenase activity in the root zone of sand-based putting greens and, in so doing, influence putting green quality.

REFERENCES

Dick, R.P. 1997. Soil enzyme activities as integrative indicators of soil health. In C.E.
Pankhurst et al. (ed.) Biological indicators of soil health. CAB international, United Kingdom.

Dick, R.P., and M.A. Tabatabai. 1992. Significance and potential uses of soil enzymes. In F.B Metting, Jr. (ed) Soil microbial ecology: Application in agriculture and environmental management. Marcel Dekker, New York.

Sylvia, D.M. 1994. Vesicular-arbuscular mycorrhizal fungi. In Methods of soil analysis.
Part 2. Microbiological and biochemical properties. SSSA Book Series no. 5, Madison, WI

Tabatabai, L.M. 1994. Soil enzymes. In Methods of soil analysis. Part 2. Microbiological
               and biochemical properties. SSSA Book Series no. 5 Madison, WI