Nanthi Bolan1,2, Surinder Saggar3, Keith McAuliffe4 and Brendon Hannan4 1Institute of Natural Resources, Massey University; 2Center for Environmental Risk Assessment and Remediation, University of South Australia, SA 5095; 3Landcare Research, Palmerston North; 4New Sports Turf Institute, Palmerston North.
The issue and the objective
There is an estimated area of 40, 000 ha of sports turf around New Zealand. Organic matter plays a pivotal role in golf course and general turf management through its influence on most processes that collectively determine 'turf health' or 'turf quality'.
The changes in organic matter arising from turf management can critically affect the performance and sustainability of golf greens. Excessive organic matter and/or thatch in the root zone can lead to rapid turf decline during stressful dry periods. This excessive organic residue may enhance disease and pest activity, reduce oxygen supply, poor/shallow rooting and localized dry spots.
Therefore, the management of organic matter accumulation is a key component of turf culture in general and golf green maintenance in particular. Excessive accumulation of organic matter in sand-based turf soils (which is often referred to as 'thatch') is detrimental to turf quality, thereby affecting the playing quality of the green. Thatch is defined as partly decomposed or undecomposed organic matter exclusively of plant origin. Thatch accumulation occurs when the rate of production of organic matter is faster than the rate of its decomposition (Beard, 1976; Beard and Green, 1994).
Thatch accumulation can be minimised through proper management practices that include adequate drainage and controlled-release fertilizer use to regulate turf grass growth rate (Callahan et al., 1997).
However, when the thatch accumulation reaches a 'threshold level', additional control measures are required. Current practices of thatch control in sports turf involves mostly mechanical/cultural measures and are primarily aimed at dilution (through topdressing with sand or soil) or removal of the thatch (through coring, dethatching and verti-cutting) (White and Dickens, 1994).
Frequent applications of these control measures are required. These thatch control methods are invariably unpopular because they are both costly and also impact the playing conditions of the green. Recently there has been increasing interest in the use of soil amendments that reputedly enhance the microbial activity of greens to induce the decomposition of thatch material (Carrow, 2004).
Over the past 5 years New Zealand Golf has supported a collaborative postgraduate research programme with Massey University, Landcare Research and New Zealand Sports Turf Institute (NZSTI).
The overall objective of this research is to examine the sustainable management of organic matter accumulation in sports turf surfaces. The research aimed at developing a process-based understanding of organic matter dynamics and refining the aspects of organic matter turnover in turf culture. The rate of accumulation of thatch in greens has been examined under different management conditions.
The nature of growing medium and the management factors (soil fertility, drainage conditions) affecting the decomposition of thatch and the mechanisms involved in controlling thatch accumulation have been examined in detail, both under controlled glasshouse and field conditions. We are also hoping to evaluate the effectiveness of commercially available thatch decomposing products under controlled conditions.
The information obtained from this research will be used for predicting the consequences of various management regimes on turf performance, and providing a scientific rationale for the interpretation of turf quality indicators.
The study has involved laboratory incubations, and glasshouse and field turf growth experiments. Firstly, soil cores were collected from a number of golf greens and other land use systems and the quantity and quality of organic matter accumulation in these cores examined.
Cores seen on right:- Figure 1. Soil cores from golf green used for the fractionation of organic matter in the thatch samples
The quantity of organic matter accumulation was measured using three different methods (loss on ignition, chemical oxidation and Leco combustion). The nature and quality of organic matter was determined using physico-chemical fractionation involving biochemical components of organic matter (e.g., lignin) and chemical pools of carbon (e.g., labile C).
Secondly, the rate of decomposition of various organic matter components in the thatch layers from various greens was examined using laboratory incubation experiments. We are also hoping to carry out a study to examine the effect of various thatch control measures, including reported thatch decomposing products on the rate of degradation of organic matter.
Characterisation of thatch and organic matter in different land-use systems
The composition of organic matter was examined using soil and thatch samples collected from different land use systems (golf greens, pasture soils, and the litter sample from the forest soil).
Twenty five soil cores were taken each from a permanent pasture, two sand based golf greens, one soil based golf green and a pine forest. The thatch layer was separated from the soil cores and the remaining soil cores were sectioned into two layers (Figure 1). The litter layer from the forest soil was also collected. A composite sample was prepared by mixing the appropriate slices from the 25 cores samples for each site.
The thatch samples and the organic matter from the soil cores were separated to light and heavy fractions using density fractionation method. All samples were analysed for organic matter content and selected samples were analysed for lignin and cellulose contents.
Microbial biomass carbon and microbial activity
In October 2005 soil cores were taken to examine the microbial carbon and microbial activity from a long-term field experiment established by NZSTI in 1997 to examine the effect of root zone and cultivation treatments on overall golf performance. The treatments included control, hydrojecting, scarifying, and vertidraining.
The microbial biomass carbon was measured by the fumigation-extraction technique (Vance et al., 1987). The microbial biomass carbon was calculated from the following equation:
Microbial biomass carbon = Eoc/Kec
Where EOC is the increase in extractable organic carbon in the fumigated soil over the non-fumigated soil and Kec represents the efficiency of organic C extraction (Sparling and West, 1988).
The microbial activity was examined for selected treatments by monitoring substrate-induced respiration from the amount of O2 consumed by a sample of soil using a Gilson differential respirometer (Macgregor and Naylor, 1982).
Characterisation of thatch and organic matter in different land-use systems
The thatch layer from the golf greens, pasture soils, and the litter sample from the forest soil contained higher level of organic matter than that of the soil layers (Figure 2). The organic matter contents of the thatch layer collected from the sand-based golf greens were less than that of the thatch layer collected from the soil-based green, the pasture soil and the forest litter.
The results also suggest that the soil-based greens, pastures and forest had higher build up of thatch material compared to the sand-based greens. These results could be attributed to faster decomposition of organic matter in the sand medium and/or to the contamination of sand in the thatch layer from the sand-based greens.
Graph on the right:- Figure 2. Organic matter content of thatch, litter and soil layers in different land use systems
The thatch samples obtained from the sand-based green contained low levels of lignin and cellulose (Figure 3). The forest litter contained the highest level of lignin, followed by the thatch layer from soil-based green and the pasture soils (Figure 3). Based on the lignin content it could be argued that the thatch material from the soil-based green is less degradable compared to that of sand-based green. However the carbon:nitrogen ratio and the lingin:nitrogen ratio values of the thatch material were less for the soil-based green than for the sand-based greens, indicating that the former is likely to degrade faster than the latter.
Graph left :-Figure 3. Lignin and cellulose contents of thatch and litter samples
The fractionation of organic matter indicates that both the thatch material and the litter sample contained low levels of exchangeable carbon compared to other carbon fractions (data not shown).
More than 50% of the organic matter obtained from all thatch and litter samples remained unextracted in any of the extractants (i.e. residual fraction), indicating high levels of carbon in structural and stabilized components. The thatch material from the pasture soil and the forest litter contained higher residual fraction levels than the thatch materials from the golf greens.
Microbial biomass carbon and microbial activity
The microbial biomass was higher in the surface layer (0-3cm) than the subsurface layer (3-6cm) (Figure 4). This could be attributed to the higher level of root proliferation in the top layer of turf grass.
The microbial biomass carbon was higher in the soil-based than the sand-based green. However when the microbial biomass content was expressed as a percentage of total organic matter the opposite trend was obtained, indicating that sand-based green provided greater microbial substrate than the soil-based green.
Graph on the right:-Figure 4. Microbial biomass in soil samples collected from the field experiment
As expected the microbial activity as measured by basal respiration was higher in the surface layer than the sub-surface layer (Table 1) and the effect was more pronounced in the soil-based green than the sand-based green. The decrease in basal respiration with depth is attributed to a lower level of organic matter in the sub-surface layer.
Furthermore the microbial activity is higher in the soil-based than the sand-based green indicating that the edaphic and micro-environmental factors governing microbial activity are more favourable in soil media. The results suggest that microbial accessibility to the thatch materials in sand-based green could be one of the factors limiting the decomposition of organic matter, resulting in the accumulation of thatch.
Table 1. Microbial activity as measured by respiration (cm3/kg/hr) for selected treatments from the field experiment
Microbial respiration (cm3/kg/hr)
0 - 3.0cm
3.0 - 6.0cm
The project represents a potentially important development for golf green management, and specifically the understanding of thatch dynamics. The project is designed to:
· Develop novel bio-physical techniques for the monitoring of thatch accumulation.
· Identify quantitative functional relationships between soil microorganisms and organic matter accumulation
· Bridge the gap between scientific knowledge and understanding about thatch accumulation as affected by current and improved management practices.
· Evaluate current and potential practices for thatch control in order to derive more effective, less disruptive processes.
· Understand the long-term implications of thatch control practices on the turf soil environment, in order to develop sustainable golf turf management models and best management practices to minimize organic matter accumulation.
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Callahan, L.M., W.L. Sanders, J.M. Parham, C.A. Harper, L.D. Lester, and E.R. McDonald. 1997. Comparative methods of measuring thatch on a creeping bentgrass green. Crop Science 37:230-234.
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Article kindly provided by the The New Zealand Turf Managenent Journal
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