We have over 25 years of experience in supplying and manufacturing sports turf fertilizer. As a consequence of the increasing cost of fertilizers we can give advice that will save you both time and money whilst also ensuring the best possible results.
We have the largest range of sports turf fertilizers in Australia for the turf and amenity markets and the following overview of nitrogen turf fertilizer sources explains your options and how they work. However, if you information on other nutrients this blog article is a good place to begin as it discusses magnesium turf fertilizers.
Quick-release sports turf fertilizer.
Despite ‘Straight’ fertilizers having the advantage of being relatively inexpensive they generally have a high salt index and therefore can damage turf if not immediately watered in. On account of being all “up-front”, they can also cause surges in growth that require increased mowing frequency.
These generally are of higher quality than simple ‘straights’ with their major disadvantages being cost and being prone to hardening or “caking”. To overcome this manufacturers often add anti-caking agents which can be abrasive to equipment. However, an advantage of these is that they allow “spoon-feeding” of turf.
As a consequence of their increased safety, enhanced efficiency fertilizers have become increasingly popular as they avoid issues with overfertilization and soluble salt damage to turf.
These are designed to improve nutrient use efficiency by minimizing nutrient losses and are divided into two groups which are slow-release fertilizers and nitrification and urease inhibitors.
Slow-release sports turf fertilizer.
|Turf fertilizer.||Factors influencing release.|
|IBDU.||Particle size, soil moisture, and temperature all play a role in release with this being 2–3 times at 27°C versus 10°C.|
|Urea-formaldehyde and Methylene urea.||The release rate is 10–12 times at 27°C versus 10°C. Large particle size and low pH have a lesser effect.|
|Sulphur-coated urea/Polymer sulphur-coated urea.||Coating thickness, coating quality, and temperature all play a role.|
The main advantages of slow-release turf fertilizers are:
- They can be used safely on turf as they have a low salt index;
- They tend not to leach into groundwater;
- A big reduction in labour costs due to being applied less frequently;
- A reduction in nitrogen nitrification and volatilization.
- As the nitrogen is not “upfront” you don’t get massive surges in growth and lastly
- You don’t get any lush disease-prone growth.
Percent slow release.
Mode of action.
Alzon Neo N.
Inhibited nitrogen and urease inhibitor.
100% polymer sulphur
21% urea; 79%
up to 6
50% urea and 50% methylene ureas.
up to 6
Polymer sulphur coated urea (PCSCU):
All of these products have nitrogen contents of 38–42%, 11–15% sulphur, and less than 2% polymer and are produced by companies such as ICL (Poly S®), and Purcell (Trikote®).
Reasons sulphur coated products have become popular are:
- Firstly, despite being coated it still results in a product having a nitrogen content of around 30–40%;
- Secondly, they reduce leaching and volatilization;
- Thirdly, sulphur is relatively cheap and lastly
- Sulphur is itself a valuable secondary nutrient.
Problems can develop if the coating cracks as the fertilizer then will just “dump” all its nitrogen and this is especially the case with the more brittle sulphur coated urea (SCU) compared to polymer sulphur coated urea (PCSCU). In fact a batch of SCU granular turf fertilizer it may contain more than 33% damaged granules and the rest be “perfectly coated” granules. Long-term use of these can also result in excessive soil acidification as a consequence of their high sulphur content.
Lastly, the temperature has a crucial role to play in the release of PCSCU fertilizers for as temperature increases, the release rate increases.
Image 1 (above). Some products marketed as lasting up to 12 weeks can release all their nutrient in a matter of days if the prill becomes damaged. Despite longevity claims, only polymer-coated urea gives anything near the claimed release period.
Image 2 (below). A lower quality sulphur coated prill that has dumped its N after cracking within 4 days of application.
Methylene urea and urea-formaldehyde.
When urea and formaldehyde are reacted in the presence of a catalyst it forms a mixture of compounds called ureaform which contains around 38% nitrogen. Several ureaforms can be separated based on their solubility in cold and hot water.
Depending on the release time, nitrogen availability can be divided into four segments based on the terms Cold Water Soluble Nitrogen (CWSN), Hot Water Soluble Nitrogen (HWSN), and Hot Water Insoluble Nitrogen (HWIN) and at a temperature of 25°C, it is the CWSN fraction that turf can absorb.
|Type of release||Approximate length of release (weeks)||Fraction|
|Moderately Fast.||3-5||Cold water-soluble|
|Very Slow.||7-10||Hot water-insoluble|
The greater the percentage of hot water-soluble and insoluble nitrogen the longer the release rate with the long-chain fractions releasing nitrogen over several weeks or months and the shorter chain fractions being available from a few days to several weeks.
While temperature has a large impact on urea-formaldehyde and natural organic products, it has little effect on IBDU and consequently, this provides good winter and early spring colour. Both the amount of moisture present and the particle size effect the amount of nitrogen released. As the surface area increases, smaller particles hydrolyze more rapidly and consequently there is a five-fold increase in N release after eight weeks when particle size decreases from 3–4 mm to 0.3–0.6 mm. One final point is that IBDU-based turf fertilizers can ‘smear’ over the surface once they become wet which is an issue on areas such as golf greens.
In Australia, IBDU is available as a sports turf fertilizer as Floranid® (BASF).
Nitrification inhibitors as sports turf fertilizer.
Umaxx® and Uflexx® are fertilizers that contain a nitrification and a urease inhibitors. To prevent nitrogen loss from volatilization, NBPT and Didin are combined with urea in order to keep nitrogen in the stable ammoniacal form for a longer period of time.
Nitrification inhibitors such as Didin and DMPP (Entec®) work by depressing Nitrosomonas bacteria in the soil which is responsible for converting ammonium to nitrite and nitrate in the soil. When soil temperatures are above 10°C, this usually takes two to four weeks. By keeping the nitrogen in the ammonium form for longer, they subsequently slow down the denitrification process thus increasing nitrogen efficiency with once being applied beginning to immediately and lasting from six to ten weeks.
Finally Piadin® is a low cost liquid inhibitor that can be applied in a spray tank with fertilizer or applied as a standalone application to a turf surface. It doesn’t damage turf and gives a high degree of flexibility with rates being 5-8L/Ha.
Research into Nitrification inhibitors has shown that DCD is a better inhibitor for clay and loamy soils, while DMPP and Piadin® are better for sandy soils.
Urease inhibitors slow down the rate at which urea hydrolyses in the soil which reduces volatilization losses of ammonia to the air. Lastly, there is no benefit from using these if rain or irrigation occur immediately.
Dual Inhibited Alzon® neo-N sports turf fertilizer.
As previously stated Umaxx® and Uflexx® contain both a nitrification and urease inhibitor. Alzon® Neo N is a dual inhibited nitrogen having an analysis of 46-0-0 and giving extended longevities of up to 10 weeks.
- It is highly soluble;
- Can be used as a granular application or by simply dissolving in a spray tank at rates down to 25Kg/Ha;
- The fertilizer does not contain a coating and instead the entire granule is impregnated with the inhibitors meaning that the actives cannot be ‘rubbed’ off.
- The resulting improvement in nitrogen use efficiency enables application rates to be cut without affecting turf growth.
- Has no residues left in the tank when used as a soluble and lastly
- The nitrification inhibitor in Alzon® neo-N reduces nitrate leaching by up to 50 % which means better value for your dollar.
Liquid fertilizers provide a much quicker response from your grass as a consequence of the nutrients being immediately available by being absorbed through the roots or leaves. Use these:
- When turf may not be growing at its maximum level such as in the middle of summer as at this time foliar uptake is pretty efficient;
- Before warm-season turf heading into dormancy and lastly
- If you want to avoid mower pick up on closely mown turf.
Their main drawback is that they do not have any longevity, although some slow-release liquids do overcome this issue. Bear in mind that you can achieve excellent results by combining both liquid and granular products as the results gained in combination are superior to relying on one method exclusively.
Slow-release Liquid turf fertilizer.
As previously mentioned there are now several slow-release liquids on the market sold under a variety of trade names such as Fertech®, Sirflor®, and Nitrosert®. All of these make claims such as:
- Longevities of up to six to eight weeks;
- Low burn potential and finally
- A high tank degree of tank compatibility.
Slow-release liquid nitrogen can be applied as a concentrated spray application on turfgrass and can also be used as the nitrogen source in mixed NPK fertilizers.
Both poultry manure and products manufactured from bio-waste offer low-cost alternatives to synthetic fertilizers, despite having issues with odour and potentially containing weed seeds. The salt index can also be an issue as a consequence of bulking up broiler chickens as during this process they are fed a high salt diet so they drink more water and put on weight faster. This subsequently passes into their droppings.
A major problem with natural organic fertilizers is that they can be highly variable and consequently release rates will vary. Organics are characterized by having relatively low nitrogen contents which are usually below 3% percent and almost all contain phosphorus. Their release is controlled by micro-organisms, which in turn are controlled by temperature and soil moisture.
Finally, products such as Dynamic Lifter®, Neutrog®, Terra firma®, and Queensland Organics® are all composed of pelletized manure and then either heat-treated or composted to remove excess moisture. The degree of composting will subsequently affect the amount of weed seed and moisture content of the final product, with final moisture levels varying from 8–16%.
Jerry Spencer wrote the Nutrition of Sports Turf in Australia.
What are the benefits of fertilizing turf?
The primary goal of the turf manager is to provide a healthy, stress-tolerant turf that can withstand a high level of wear, however, to subsequently achieve this, selecting the correct fertilizer regime is important as this has a major influence on turf health. Too much nitrogen and the turf can become extremely prone to disease and have a low tolerance to wear while too little nitrogen and recovery and growth are limited.
Sometimes excessively high nitrogen applications are made or it is applied at the wrong time. This results in turf that is prone to Pythium sp, patch and leaf spot diseases, excessive thatch production, increased water usage, and the need for increased mowing. Additionally, over-fertilization, especially with water-soluble forms of nitrogen can burn turf. Other issues include reduced root, rhizome, tiller, stolon growth, and reduced heat and drought tolerance.
Nitrogen-deficient turf is less dense which encourages weed encroachment and several diseases, such as dollar spot or red thread. Finally, nitrogen-deficient turf grows slowly, producing fewer leaves and tillers.
What do the letters and numbers on a bag mean?
Turfgrass requires at least 16 nutrients for normal growth and development with some nutrients being needed in large amounts whilst others are required in much smaller quantities. Every fertilizer bag should have the nutrient analysis marked as N, P, K, S, Mg, Ca, and whatever trace elements are present. These stand for nitrogen, phosphorus, potassium, sulphur, calcium, and magnesium respectively.
In Australia, we use the elemental labelling system for nutrient analysis while in Europe and the USA the oxide analysis which can subsequently lead to some confusion. The nitrogen figure is the same with both systems but P, K, etc. are different.
Using potassium nitrate as an example this is labelled as 13-0-36 in Australia and 13-0-43 in the USA even though it’s the same product. Consequently to go from:
- Elemental K to the oxide form divide by 0.83 (or multiply by the inverse, 1.2).
- To go from elemental P to the oxide form, simply divide by 0.44 (or multiply by the inverse, 2.27).
- Similarly, to go from Ca to CaO, divide by 0.715 (or multiply by 1.39), and
- Finally to go from Mg to MgO, divide by 0.602 (or multiply by 1.66).
When is the best time to fertilize turf?
This is a massive topic in itself and there isn’t any one answer. Generally, the best time for lawn fertilization is in the spring when the soil temperature reaches 10ºC as this stimulates growth heading into the summer.
On the other hand Autumn fertilization of warm-season turf increases turf density by encouraging the production of new tillers, rhizomes, and stolons together with more shoot growth from existing turf. If you have overseeded it will also help promote the growth of the young seed and consequently promote the production of carbohydrates helping turf survive the stresses of winter and encouraging spring growth.
However, on golf course greens regular light feeding throughout the year can have benefits in helping to counter disease and encourage recovery.
How often should you carry out soil testing?
Soil testing is defined as a measurement of the soil to identify nutrient deficiencies, predict nutrient needs, and evaluate potential excesses. Soil samples can be taken at any time of the year but not within two weeks of any application of a fertilizer containing phosphorus, magnesium, potassium, or calcium. The frequency of testing can be every year but, unless you are addressing a particular problem, every three years is ideal.
How do I know I have a good quality sports turf fertilizer?
With granular fertilizers, excessive dust, a lack of particle uniformity, being damp to the touch, and smearing inside the fertilizer hopper are all good indicators of poor quality or incompatible ingredients having been used in its manufacture. Likewise, with liquids, any residue at the bottom of the drum and filter blockages can be indicative of issues.