Reducing Nitrogen Use
Amenity turfgrass is used in a wide range of facilities such as athletic fields, parks, home lawns and of course golf courses. Numerous grass species are used, including C3 (cool-season) and C4 (warm-season) grasses and all require relatively high fertility inputs to maintain health and provide quality playing surfaces.
Nitrogen (N) is the nutrient applied in the highest quantity to golf course turfgrass, with application rates varying based on the component of the golf course (i.e., greens, tees, fairways, or roughs). Over the past number of years, however, the trend has been toward lower N use rates, as a practical example when I first started in the turf business in the 1980’s, the annual N input on the greens at the facility was 450 kg/ha (400lbs/acre)!!
Lowering N inputs is good news and makes sense for many reasons. From an environmental perspective a high level of N can have detrimental ecological effects, for example on macroinvertebrate community structures, increased algal biomass, and increased eutrophication.
From a turfgrass management perspective, excessive N will be lost via volatilization and leaching, basically wasting your budget, very significant with the current increases in fertiliser costs! Also, excessive N applications can lead to lush, disease susceptible swards with unacceptable playing qualities. And of course, excessive N inputs, especially on greens, can lead to the buildup of organic matter…Thatch! Simply put, thatch is caused when the grass is growing and being cut faster than it can be decomposed and, apart from reducing the quality of the playing surface, thatch is a significant source of many disease inoculum.
However, as with life, a balance is required, eliminating, or reducing N to a lower than optimum amount can lead to poor levels of growth, turf thinning, and slow recovery from wear and damage. So, getting the N inputs right requires knowledge and experience.
How can you reduce N inputs while still maintaining quality surfaces?
Firstly, determine what your N requirements are! Soil testing is the traditional method when determining nutrient requirements, and remains a common nutrient management tool. But one size doesn’t fit all, and numerous factors need to be considered when determining N requirements. Factors such as, grass species, area of use (i.e., greens, tees, fairways, rough), geographical location and environmental conditions, amount of traffic, time of year, nature of the rootzone. This is where using turf growth potential, which incorporates site-specific weather and turf type to calculate nitrogen demand comes into its own and is an excellent method of determining N requirements.
Once you have calculated the amount of N needed you then have to ensure its applied correctly and at the optimum rate and time.
Calibration, all facilities should make the effort to calibrate equipment prior to applications. Although this process may require additional time, the potential money savings and increased risk mitigation justifies the process.
Nitrogen source and application timing: consider your source of N, the use of slow-release N products are commonly used, these allow for reduced labour costs, since the number of applications are reduced. As well as reducing the risk of foliar burn, they can provide an even supply of N, and reduced leaching. However, some slow-release sources, especially ureaformaldehyde (UF) and natural organics, such as Milorganite, which require soil microbial activity to become available to the plant, give only poor to moderate response in cool weather. Other slow-release sources, such as isobutylene diurea (IBDU) and sulfur coated urea (SCU), are not as dependent on soil microbial action; therefore, release rates are not significantly decreased in cold temperatures.
A water-soluble source of N has a higher leaching potential than a slow-release source, especially when its application is followed by a large amount of water, either from rainfall or irrigation.
Foliar applications are an ideal method to apply exact amounts of N directly to the plants, advantages being the plant uses them as soon as they’re applied, using turf growth potential you can spoon feed to fully control growth. Foliar fertilisation allows you to reduce the total amount of N applied and when compared to traditional granular inputs, foliar treatments are much more efficient.
The use of foliar applied nanoscale liquid sprays containing N can also significantly enhance N utilisation and efficiency. Nanoparticles are organic, inorganic or hybrid materials with a particle size ranging between 1 and 30 nm which is approximately 1000 times smaller than most conventional product particle sizes! The N is adsorbed onto nano-silica molecules, which prevents bonding with each other with water. With conventional fertilisers 40-70% of the N can be lost to the environment, but nanotechnology allows for a higher accumulation of N in the plant and less loss to the surrounding environment.
Applying just the correct amount of N for your individual facility makes sense.
It’s good for the environment, ensures your surfaces are the way you want them, and it save you money!
Take home points:
- Excessive N will have detrimental affects of the ecosystem, will not provide the playing standards you require, will waste your money, and can lead to excessive organic matter and increased disease pressures.
- Decide the form and rate of N tailored for your specific site.
- Use Turfgrass Growth Potential to ensure conditions are suitable for N applications.
- Calibrate your equipment, this makes sense financially and environmentally.
- Ensure heavy or prolonged rain is not forecast prior to application.
- Consider using foliar applications linked to growth potential to spoon feed N when it is most required.
- Consider the use of nanotechnology based products to improve the efficiency of inputs and minimise losses.
Dr. John Dempsey
Independent Turfgrass Research
Email: [email protected]
Web: https://orcid.org/0000-0002-4745-1541