Being sports turf consultants we believe that getting turf nutrition right is the cornerstone to turf management. Just like the human body if you eat poorly you are going to become unhealthy, more susceptible to disease and not perform at your best. These principles apply to turfgrass. Besides this fertiliser has historically been a lot cheaper than using turf chemicals.
As sports turf fertiliser suppliers we have a wide range suitable for all your requirements whether they be greens, fairways or sportsgrounds. As a guide, the following explains how nitrogen fertilizers work and where they should or shouldn’t be used.
If you need more information on other nutrients these blog articles will be of interest.
Quick-release sports turf fertilizer.
‘Straight’ fertilizers are relatively low cost option. However, they generally have a high salt index and can damage turf if not immediately watered in. They also cause growth surges that will mean grass will need mowing more often.
These are of higher quality than ‘straights’. Besides their cost, these are also prone to hardening or “caking”. To overcome this anti-caking agents are often used which can be abrasive to spray equipment. However, an advantage of the water solubles is that they allow “spoon-feeding” of turf. This means a little and often can be applied so that grass is fed exactly what it needs and when it needs it.
As a result of the above problems, enhanced efficiency fertilizers have become popular. This is due to a several factors:
- Firstly, their increased safety. There is less chance of damage to turf;
- Secondly, they last longer and finally
- There is no big surge in growth needing more mowing.
Enhanced Efficiency sports turf fertilizer (EEFs).
EEF‘s improve nutrient use efficiency by minimizing nutrient losses. They are divided into two groups. Slow-release sports turf 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. For example, release is 2–3 times faster at 27°C compared to at 10°C.|
|Urea-formaldehyde and Methylene urea.||The release rate is 10–12 times faster at 27°C compared to at 10°C. Also large particle size and low soil pH have less of an effect compared to IBDU|
|Sulphur-coated urea/Polymer sulphur-coated urea.||Coating thickness, coating quality, and temperature all play a role.|
The main advantages of slow-release fertilizers are:
- They are very safe to use as they have a low salt index;
- Secondly, they tend not to leach;
- Thirdly, as they are applied less often it means a reduction in labour costs;
- They reduce waste by minimizing nitrification and volatilization;
- You don’t get massive growth surges and
- Lastly, there is no lush disease-prone growth.
Table showing commonly used Enhanced Efficiency sports turf fertilizer (EEFs).
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 have nitrogen contents of 38–42%, 11–15% sulphur, and less than 2% polymer. Sulphur coated products have become popular sports turf fertilisers because:
- Firstly, they have a high nitrogen content of around 30–40%;
- Secondly, they reduce leaching and volatilization;
- Thirdly, sulphur is relatively cheap;
- 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. This is likely with the more brittle sulphur coated urea (SCU) compared to polymer sulphur coated urea (PCSCU). In fact a batch of SCU granular turf fertilizer may contain more than 33% damaged granules and the rest be “perfectly coated” granules. This means that you would be paying a premium price for a product which is 33% “up-front”. Long-term use of these can also result in increases in soil acidification due to their high sulphur content.
Lastly, the temperature has a crucial role to play in the release of PCSCU fertilizers. As temperature increases, the release rate increases.
Image 1 (above). Some coated sports turf fertilisers claim to last for 12 weeks. These release all their nutrient in a matter of days if the prill becomes damaged. Despite many longevity claims, only polymer-coated urea gives the claimed release period.
Image 2 (below). A lower quality SCU prill that has dumped its N within 4 days of application.
Methylene urea and urea-formaldehyde sports turf fertilizer.
Ureaform contains around 38% nitrogen. During its manufacture 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 amounts of Cold Water Soluble Nitrogen (CWSN), Hot Water Soluble Nitrogen (HWSN), and Hot Water Insoluble Nitrogen (HWIN). At a temperature of 25°C, it is the CWSN fraction that turf uses.
|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. The long long-chain fractions release nitrogen over several weeks or months and the shorter chain fractions are available from a few days to several weeks. This is the science behind many MU and UF based sports turf fertilisers.
Temperature has a large impact on both urea-formaldehyde and natural organic products. However, it has little effect on IBDU. Consequently, in cooler weather this provides good winter and early spring colour. Both the amount of moisture present and the particle size affect the amount of nitrogen released. As the surface area increases, smaller particles hydrolyze more rapidly. 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. In addition to this, IBDU-based fertilisers can ‘smear’ over the surface once they become wet which is an issue in areas such as golf greens.
In Australia, IBDU is available as a sports turf fertiliser as Floranid® (BASF).
Nitrification inhibitors as sports turf fertiliser.
Nitrification inhibitors for example Didin or DMPP (Entec®), work by depressing Nitrosomonas bacteria in the soil. These microbes are 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. Once applied they last from six to ten weeks. They do not kill soil microbes but instead slow them down.
Piadin® is an economical liquid nitrification inhibitor that is applied with a turf fertiliser or as a standalone application to a turf surface. It doesn’t damage turf and has a high degree of flexibility with rates being 5-8L/Ha.
Research into the use of Nitrification inhibitors as turf fertilisers has shown that DCD is a better inhibitor for clay and loamy soils, while DMPP and Piadin® are better for sandy soils.
The sports turf fertilisers Umaxx® and Uflexx® contain both a nitrification and a urease inhibitor. To prevent volatilization losses, NBPT is combined with urea. Urease inhibitors slow down the rate at which urea hydrolyses in the soil. This keeps nitrogen in a stable form for longer so slowing down the rate of urea hydrolyses in the soil. This in turn, reduces volatilization losses of ammonia to the air. There is no benefit from using these if rain or irrigation occurs immediately. So if your irrigating immediately after applying your fertilizer your paying for something you don’t need.
Dual Inhibited Alzon® neo-N sports turf fertilizer.
Alzon® Neo N is a dual inhibited nitrogen sports turf fertiliser and has. a 46-0-0 analysis. It gives longevities of up to 10 weeks.
- It is very soluble;
- Can be used as a dry granule or by simply dissolving in a spray tank. Rates are as low as 25Kg/Ha;
- As this is not a coated fertiliser and instead the entire granule is impregnated, the inhibitors cannot be ‘rubbed’ off;
- Due to the improvements in nitrogen efficiency, application rates to be cut with no detriment to turf growth;
- No residues are 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 it saves you money.
Liquid sports turf fertilisers give an instant turfgrass response. This is because of nutrients being immediately available and 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. This is when foliar uptake is efficient;
- Before warm-season turf 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 as discussed below there are some slow-release liquid fertilizers. Personally I believe in getting the best of both worlds by using a combination of liquid and granular products. The results gained in combination are better than relying on one approach exclusively.
Slow-release Liquid sports turf fertiliser.
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 have the following characteristics:
- Firstly, longevities of up to six to eight weeks;
- Secondly, low burn potential;
- Thirdly, a high tank degree of tank compatibility.
Slow-release liquid nitrogen can be applied as a spray application onto turfgrass and are also used as the nitrogen source in mixed NPK ;iquid fertilizers.
Poultry manure and products manufactured from bio-waste are low-cost alternatives to synthetic sports turf fertilisers. However, they cannot have issues with odour and weed seed content. As well as that the salt index can be an issue as a result of bulking up broiler chickens. As the chickens grow they are fed a high salt diet. This means that they drink more water and so put on weight faster. This then passes into their droppings.
Another major problem, is that they have a highly variable analysis. Due to their very nature you cant produce a consistent analsysis fertilizer from manure alone. Organics are characterized by having low nitrogen contents. These are usually below 3-5% and almost all of these also contain phosphorus. Their release is controlled by micro-organisms, which in turn are controlled by temperature and soil moisture.
Products such as Dynamic Lifter®, Neutrog®, Terra firma®, and Queensland Organics® are all made from pelletized poultry manure. This is then either heat-treated or composted to remove excess moisture. The amount of composting affects the amount of weed seed and the final moisture content which can vary from 8–16%.
Why fertilize turf?
The aim of anyone growing sports turf is to provide a healthy, stress-tolerant turf that can withstand a high level of wear. Key to achieving this is selecting the correct fertilizer. 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. Too little nitrogen and recovery and growth are limited.
What do the letters and numbers on a fertilizer bag mean?
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, magnesium and calcium respectively.
In Australia, we use the elemental labelling system for nutrient analysis. In Europe and the USA they use the oxide analysis. This can 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, At this temperature things are just beginning to grow so need feeding. Feeding at this time will get the turf growing nicely heading into the summer.
Autumn feeding of warm-season turf increases turf density. It does this by encouraging new tillers, rhizomes, and stolons together with more shoot growth. If you have overseeded it will also help promote the growth of the young seed and consequently promote the production of carbohydrates. This in turn helps turf survive the stresses of winter and encourages spring growth.
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 usedl 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 two years is ideal.
Whats a quality 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.