Spring forward with the right fertiliser in play

Nitrogen is essential for plant growth but low temperatures in early spring can cause significant problems. Kelly-Marie Clack from Origin Amenity Solutions says that applying a foliar application of nitrate or ammonium is a known solution to this, and the R&D team has been conducting trials to find out what mixture of the two works best on what surfaces.

Selecting the ideal fertiliser can be a tricky task, so make sure you understand what you are trying to achieve before applying the fertiliser. In early spring when soil temperatures tend to be low, we can not rely on soil microbes to break down nitrogen to make it available for the plant. It is therefore essential we understand which nitrogen sources are available to the plant when applied and what we can expect to see when we apply the product.

Nitrogen is absorbed through the roots in solution form, as ammonium (NH4+) or nitrate (NO3-). The nitrogen is classed as plant-available therefore applying a fertiliser containing these forms gives a relatively quick turf response.

If the ammonium is not taken up by the plant it will sit in the cation exchange until it is required by the plant for growth, or it will go through the nitrification process. This is when ammonium is converted by nitrosomonas bacteria into nitrite (NO2-) and then nitrobacter converts this into nitrate, which as we know is plant-available, but this process also requires soil temperature.

Organic fertilisers and soil organic matter must go through a process called mineralisation. Soil microbes will break down the organic nitrogen into ammonium which is then available to the plant to utilise for growth. Soil temperatures need to be above five degrees for mineralisation to take place. Likewise, urea requires soil temperature for urease enzymes to convert the urea into ammonia (hydrolysis.) Ammonia is a gas that can volatilise but, fortunately, hydrogen in the soil converts ammonia into ammonium for plant uptake. These nitrogen sources have to be changed before they can be used by the plant for growth. Therefore the turf response is much slower with very little visual impact.

To summarise:

• Nitrate and ammonium sources of nitrogen are available instantly. Perfect for cool temperatures.

• Organic and urea must be converted to be made available for the plant so consider the soil temperature.

For rapid nitrogen uptake, you can apply a foliar application of nitrate or ammonium.

A trial was conducted at OAS Turf Science and Technology Centre in early 2022 to look at the differences in turf response to different nitrogen sources in cold weather. Two treatments were applied; one was a combined ammonium and nitrate source, and the other was straight urea.

Select a granular or liquid fertiliser containing nitrate nitrogen or ammonium nitrogen in cool weather conditions to encourage growth, sward density and improved aesthetics. Origin Amenity Solutions offers a range of products containing both nitrate and ammonium for rapid uptake. Selecting the total quantity of nitrogen to apply should be based on the growth and recovery required to improve consistency and performance following the winter season.

Final digital images from the trial on April 6: Rapid Response plot on the top showing higher quality compared to Urea plot in the middle and untreated control on the bottom. Both Urea and Rapid Response plots received the same level of nitrogen over the trial

For example:

Applying 35g/m2 of ColdStart 11.5.5 +8%Fe is 38.5kg of nitrogen per ha, whereas an application rate of 25g/m² is 27.5kg of nitrogen per ha.

Products such as Greentec 6.5.18 + 4%Fe at 35g/m² applies 21kg of nitrogen per ha and at 25g/m² delivers 15kg/ha. This product also contains less iron than Coldstart if your soil samples indicate high iron levels.

Applying rapid response liquid at 30L/ha achieves 4.8kg of nitrogen per ha.

If you require any support when selecting your spring fertiliser please contact your Origin Amenity Solutions area manager for advice on 0800 138 7222 or email sales@originamenity.com