Effects of microorganisms on thatch decomposition and turf growth-promotion in golf course field

Abstract

Thatch is a layer of partially decomposed organic matter between turf green shoots and the soil surface. It is formed primarily from periodically sloughed-off roots and residue of horizontal stems (stolon and rhizomes), stubbles, and mature leaf sheaths and blades. Excessive thatch (>5.07cm) makes an adverse effect on turfgrass management that causes difficulties in mowing, fertilization, irrigation, and pest control. Since golf fields are maintained at low mowing heights, golf course greenkeepers face the difficult task of producing a high quality, stress-tolerant turfgrass with an acceptable putting distance or speed. There are numerous dethatching techniques including various mechanical practices such as vertical mowing, core cultivation, grooming, and topdressing to reduce thatch accumulation. However, these techniques are less effective and require high cost, time consuming and labor-intensive practices. This study aimed to select microorganisms that can be used for the biological decomposition of the thatch layer. For this, soil samples were collected from eight golf-course fields from which a total of 53 soil bacteria were isolated. Among these bacterial isolates, ten isolates showed cellulose-degrading activity in carboxymethyl cellulose assay at 25oC, among which five were selected for further studies because of their cellulose-degrading activity regardless of the temperature conditions from 21~28 oC. These bacterial isolates were identified as members of the genus Bacillus based on 16S rRNA gene sequencing analysis and morphological characteristics revealed by electron microscopy. Among these, three isolates (A1, F1, and H4) were more efficient for moisture retention, root growth and plant density promotions, which may be related to the reduction of thatch accumulations. These activities were validated in nursery experiments: For the thatch layer thickness, the three bacterial isolates were more efficient in reducing its thickness same as a commercial microbial product, Thatch Manager (TM) than the non-treatment control without the promotion of the green quality like putting speed and distance, but for the matter of plant-growth characteristics, bacterial treatments showed higher chlorophyll index related to visual quality of the green at one week after treatment (WAT) than TM and non-treatment control

root length increased continuously more in bacterial treatments and control than TM. All of the aspects suggest that the three bacterial isolates may be developed as microbial products for the reduction of thatch layers in greens and for increasing the green visuals as well. The bacterial isolates are the residents of the golf course fields, so there will be no problem for them to be established to colonize the golf course fields.