January 2007

1 Boopathy, R. et al., 2001. Microbial Decomposition of Post-Harvest Sugarcane Residue. Bioresource Tech. 79:29-33

CREEPING BENTGRASS PUTTING GREEN THATCH DECOMPOSITION THROUGH SYSTEMATIC SURFACE APPLICATION OF I-MOLTM

Prepared by: Max Schlossberg, Ph.D., Asst. Prof. of Turf Nutrition & Soil Fertility (mjs38@psu.edu), and Dave Moody, MS Soils Graduate Student. The Pennsylvania State University Center for Turfgrass Science Introduction: Accumulation of thatch is generally undesirable yet inherent to intensively-managed turfgrass systems. Thatch accumulation has become a more serious concern with the increased use of new, high-density and aggressively-growing turfgrass varieties. Though thatch accumulation is traditionally mitigated through cultural practice (topdressing) and physical cultivation techniques (e.g. verticutting and/or core aerification), these procedures are labor-intensive and disrupt playing quality. Moreover, the recognized long-term benefits of physical cultivation can be offset in the short-term by tissue desiccation and/or increased damage from pests like cutworm, and in the long-term by surface redistribution of viable weed seed from depths of the soil seed bank. For these reasons, there has long been interest in products that can effectively control thatch without causing the physical disruptions. Over the last several decades, products containing ‘bioactive’ ingredients like enzymes, active cultures, and/or plant hormones have been introduced for this purpose. Application of active culture, like most biological control methods, has not been proven sustainable under field conditions. Likewise, use of enzymes and/or hormones has demonstrated mixed results. Use of nutrient-rich, labile, carbon substrate sources, a true cultural control method, has naturally enhanced the population and activity of indigenous soil microbes in a recent study1. Similar results show these applications to significantly increase decomposition rate of lignified, cellulose-rich organic residues. I-MOLTM, From The Ground Up, Inc.'s own proprietary liquid blend of molasses and iron sulfate, is a non-living, labile carbon substrate containing numerous essential plant macro- and micro-nutrients that serve as a food source for microbial populations. Experimental Objective: To closely monitor the effectiveness of systematic I-MOLTM treatments on the rate of bentgrass putting green thatch/surface organic matter decomposition under controlled laboratory conditions, and to measure any influence of fungicide tank mixing on the overall effectiveness of I-MOL treatments. Methods: The authors took a seemingly-untraditional approach to measuring thatch control in this study. Accurate measurement of thatch is an incredibly difficult endeavor, and is prone to spatial and sampling error that often renders data from field experiments inconclusive. Thus, we elected to determine thatch decomposition rate in a flow cell system where real-time CO2 evolution could be measured with 0.1 milligrams-carbon accuracy. Following collection of heavily-thatched creeping bentgrass plugs (right) from a sand-based putting green (Cape May County, NJ, USA), all eleven (11) were treated with a low-volume application of Roundup herbicide. Two weeks later, all aerial plant tissues (leaves, tillers, shoots) were removed, and plug surfaces were treated with either I-MOL (3 oz./M), I-MOL + Daconil (3 and 1 oz./M, respectively), or a positive control containing the exact concentration of nutrients in I-MOL, but without carbon (3% Fe, K; 2% S; 0.5% N & Ca; all others <0.2% by mass). Treatment delivery was made in a 3 gal./M application and watered-in (0.04”).

January 2007

Pennsylvania State University 2006 Turfgrass Research Report—M.J. Schlossberg & D.R. Moody 2

Days0 4 8 13 17 21 25 29 33 38 42 46

Net

Evo

lved

C (l

bs C

/ 10

00 ft

2 )

2

4

6

8

10

12IMOL + DaconilIMOLControl (+IMOL nutrients)

Immediately following treatment application, each plug was encapsulated in its flow cell for a 7-day period of CO2 evolution monitoring. Treatment reapplication to the plugs was repeated 5 more times (6 weeks total), before removal and storage of the treated plugs for destructive analysis of organic matter (OM), cellulose, hemi-cellulose, lignin, and microbial-enzyme concentrations. The described 6-week run was repeated twice using fresh plugs.

The low flow rate of the constant-flux experimental system used pressurized ultra-pure (CO2-free) air to prevent CO2 buildup and suboptimal oxygen levels. Except the gaseous CO2 residing within pores of the plug (assumed to be equal across all cores removed from the identical putting green on the same day), microbial respiration comprised the sole future source of CO2 evolution from each plug (flow-cell). In soil devoid of viable root tissue, microbial respiration is a direct measure of microbial activity, which in turn relates to the sheer number of microbes assimilating carbon. Under ambient and aerobic conditions, the rate of soil microbial respiration quantifies organic matter (OM) decomposition rate. Considering all treatments were surface-applied, recorded levels of CO2 evolution relate directly to the microbial decomposition rate of OM in the surface soil/thatch of the putting green. Levels of CO2 evolution were converted to carbon and adjusted for weekly additions of labile carbon substrate within the I-MOL and I-MOL + Daconil treatments. Thus, calculated differences are ‘net’ treatment effects reflecting decomposition of only original thatch/organic matter (OM) by the indigenous soil microbe population.

Results: Carbon evolution resulting from the I-MOL treatment, again directly related to microbial OM decomposition, significantly exceeded that of the positive control plugs by 17.6%. This amounts to a 2 lbs/M difference in carbon evolution over a 6-week period of use. Each data point shown represents a mean value of three independent 6-week experiments (left). Depending on specific thatch properties, the observed benefit could amount to a difference of 3 lbs OM/M (assuming thatch OM to be 67% C by mass).

Destructive analysis of the experimental plugs is underway. Additionally, the described study is being repeated with heavily-thatched plugs collected from a mineral soil fairway, with all treatments being made in combination with Daconil fungicide. A complete report of all experimental results will augment this data and summarize the thatch control efficacy of systematic I-MOL treatments. When complete, we encourage interested parties to access the final report and conclusions at either the Pennsylvania Turfgrass Council (www.PAturf.org) or I-MOL (www.I-mol.com) website(s). Acknowledgements: The authors sincerely thank the West Virginia Golf Course Superintendents Assn., The Pennsylvania Turfgrass Council, and From The Ground Up, Inc. for their support of this described research.