So How Can We Increase Spring Grass?

Soil fertility is one of the key pillars to growing early spring grass. Phosphorus (P) is one of the major elements in driving early grass, along with the other elements such as soil pH, Nitrogen, and Sulphur.

With soil fertility, particularly phosphorus levels, being in focus in recent years, it is important not to take phosphorus for granted when it comes to spring grass. Having sufficient phosphorus in the spring fertiliser programme is essential for two reasons:

1) Phosphorus is critical to kickstart grass growth in spring

2) Phosphorus availability in soil is lower in cooler soil temperatures in spring

Therefore, it is essential to get phosphorus fertiliser out early in the spring to help spring growth. Teagasc recommends applying a minimum of between 50 – 75% of the total P for the year in the early spring period in advance of spring growth.

For years, traditional phosphorus fertiliser ingredients being used in NPK blends have remained very similar, with little advancement in improving the efficiency of fertiliser phosphorus. These traditional forms of phosphorus fertilisers help to drive this spring growth, but the efficiency of their use by the grass can be affected by high levels of lock-up by the soil, especially in low P Index soils, low pH soils, and soils with high iron and aluminium levels.

A new form of phosphorus, called TOP-PHOS, is now available that can help overcome these issues to grow more grass in spring.

So what is TOP-PHOS?

TOP-PHOS is a brand new form of Phosphorus fertiliser which will be available in 2018. It is a revolutionary new Phosphorus technology that has been developed by Groupe Roullier and available in Ireland from Grassland AGRO. TOP-PHOS is a new and unique chemical form of phosphorus compared to standard P fertilisers, and has been recognised within the EU REACH regulations as being different to the traditional forms of P used in standard fertilisers.

TOP-PHOS is a new fertiliser ingredient called Complex Super Phosphate (CSP). It is a water soluble phosphorus fertiliser, and is therefore available quickly for uptake by the grass. However, unlike standard forms of phosphorus, the chemical make-up of TOP-PHOS protects it from being locked up by the soil. This maximises the availability of P to the grass. TOP-PHOS also contains stimulants that are designed to increase root mass to improve P efficiency and to increase soil microbial activity to release P from the soil reserves.

So How Does TOP-PHOS Help Spring Grass?

Figure 1. The effect of using TOP-PHOS compared to standard P fertiliser on spring grass yield

Figure 1. The effect of using TOP-PHOS compared to standard P fertiliser on spring grass yield

Phosphorus availability in soils is always challenging, particularly in the cooler soil temperatures in spring. TOP-PHOS increases the availability of P and will therefore increase spring grass growth, as more of the P applied can get to the grass faster to kickstart growth. On-farm Irish trials in 2017 evaluating the benefits of TOP-PHOS for spring grass growth showed an extra 0.4 tonnes of grass DM per hectare in the Jan to early April period where TOP-PHOS was used as the source of P compared to standard P fertiliser. This results in a return of €72/ha of spring grass grown by using TOP-PHOS.


TOP-PHOS also has the advantage of allowing greater flexibility when designing a spring fertiliser plan as it is a fertiliser containing both phosphorus and sulphur in the same product. A single application of TOP-PHOS in early spring can help to simplify the overall spring fertiliser programme by getting both phosphorus and sulphur out together, thereby simplifying the remainder of the spring fertiliser rounds to straight nitrogen (e.g. Urea or CAN). This has the advantage of making fertiliser management in spring more simple and straightforward.

For more information on how TOP-PHOS can help you grow more grass this spring, contact your local Grassland AGRO technical advisor or Dr. P.J. O’Connor on 086 3237894.