Lark Hill turf recovery
By Neville Passmore
Lark Hill Sportplex Port Kennedy.
Sting nematodes are a fairly new problem in turf. Industry professionals have been aware of their lawn hungry ways for someyears but it is only recently coming to the attention of home gardeners.
This microscopic worm-like critter likes low nutrient, sandy soil just like you find in many Perth gardens. When in plague proportions they eat up the roots of turf causing the grass to collapse turn brown and then die.
Most of the major ovals and parks around Perth were established with very little organic matter added to the sandy soil. Because of this they are prone to drying out in summer and require high rates of irrigation to keep the appearance up. This increases the leaching of nutrients and lowers fertility creating an ideal environment for a population explosion of sting nematodes.
Paul Smith the curator of Lark Hill Sportsplex in Port Kennedy was facing a major dilemma a couple of years back when these nematodes invaded his turf. The Sportsplex covers 24 hectares of active playing turf and cost $28 million to construct. This is a major sporting facility for the Rockingham, Peel region community where rugby, soccer, hockey, softball and cricket are played. Games are played every weekend throughout the year and training sessions are undertaken virtually every weekday.
Constructed on a sand dune and being a coastal location, the playing fields are subject to high winds throughout summer with extended heat stress periods above 35 degrees C. Hot easterlies and drying sea "breezes" during this season can lead to wilting of the grass. Couch grass turns blue.
After these wilting events, high irrigation rates were needed for up to 10 days to recover the grass condition. This remedial watering needs to occur as quickly as possible to minimise damage to the playing surface through wear and tear. All of this was occurring against a background of limited water resources.
Paul wanted to combat the sting nematodes particularly in the rugby pitch. There are chemical controls available but there are many downsides to this approach. The chemical is highly toxic, a serious issue from the point of view of the safety of his staff who would have to apply the spray and those playing on the grounds. This solution was dismissed.
Research showed that increasing soil carbon through the application of mature composted materials could be of value so Paul contacted Andy Gulliver from C-Wise to come up with a whole system approach that looked at the underlying issues of soil health and fertility. The recommended treatment consisted of an application of compost derived organic carbon to control the nematodes in a way that would not interfere with the heavy usage of the grounds.
A targeted renovation treatment program was devised for the rugby pitch covering an area of 7000m2 that was badly affected by sting nematodes. The grass was showing little growth and poor recovery from wear in addition fungal disease was starting to add to the woes and some parts were becoming dangerous to play on. The biggest concern was keeping the ground in a safe playing condition through to the Grand Final.
C-Wise prepared a humus rich compost designed to build soil carbon, improve soil water holding capacity, and provide a complete balance of nutrients and trace elements together with high levels of humic and fulvic acids to promote root growth and drive nutrient uptake. These conditions promote a healthy soil biology, healthy plants and reduce pests and disease – including those pesky nematodes.
The rugby pitch was hollow tyne cored, which means that that small cores were extracted leaving small holes. Organic carbon was applied at a rate of 100 cubic metres per hectare, the equivalent of 10 litres per square metre. This was mechanically rubbed into the turf and the core holes.
Within weeks of the treatment the colour of the grass was significantly better and the density of the growth was also dramatically improved. The increase in the mowing height and frequency showed clearly that growth had been restored. Paul said "since treating the rugby pitch, top up fertiliser applications have been pushed out by 2 to 3 weeks, reducing the number of applications from 8 to 6, a saving of 25% over the year". The best news was that the finals for the season were played at Lark Hill to the great relief of all.
Turf roots in the treated pitch extended down to 30 cmcompared to around 10 cm in areas that had not received the composted material. In hot weather the benefit of this deeper root system was seen in faster recovery and the use of less water.
Core samples taken 15 months after the compost treatment showed more than a 90% reduction in nematode numbers down from 1000 per square metre to only 25. At this reduced level these pests don't do noticeable harm.
The pitch is looking in great condition some year and a half after treatment and is recovering brilliantly from the unceasing wear and tear from near constant sports usage.
Home gardeners can draw some real lessons from Paul Smith's Lark Hill work even though very few of our lawns get to have burly rugby players scrumming and making hairpin turns. By applying high humus, composted, organic carbon to the lawn you can improve the performance and appearance long term and use less water and fertiliser at the same time. Paul's advice is "get the soil right and the grass will stay healthy and feed off the soil.
And one of the other benefits? After the hottest summer on record not only has Paul’s turf grown well, he has used over 20% less water. What a great win for both the sports community and the environment.
The rugby pitch today looks in great shape.
The new Hockey pitch. soil was improved before planting. this is the most successful pitch at the complex.