Finish the season with N
Make the most of the last chance to get pasture in good shape for spring.
The impact of summer and the need to get stock in good condition before winter, may have taken a toll on pasture covers. By addressing this now, pasture will be primed to deliver good levels of feed in spring when it is most needed.
Which N is best?
There are many nitrogen fertiliser options available and it can be a little bewildering. Urea has been the traditional choice but has some downsides, particularly in relation to potential losses from volatilisation - the process by which applied nitrogen is lost to the atmosphere as ammonia gas. Soil temperature and moisture both impact the level of volatilisation that occurs, and it is important to understand these when choosing your nitrogen product.
Soil temperature: Many assume that volatilisation only happens in very warm, dry conditions. However, various studies have shown that volatilisation still occurs at lower soil temperatures.
Grass growth is temperature dependent, which is why recommendations suggest that soil temperatures should be consistently above 6°C at 9:00 am before applying nitrogen. This temperature is more likely to occur in autumn opposed to late winter or early spring, leading into a more positive pasture response when nitrogen is applied.
Soil moisture: 5-10 mm of rain or irrigation within eight hours of application is critical to minimise volatilisation losses. On the other hand, rainfall or dew before application will not prevent losses.
Autumn rainfall can be unpredictable, so it makes sense to protect the nitrogen investment by using a product from the SustaiN range. SustaiN is a specially formulated nitrogen fertiliser that reduces nitrogen losses from volatilisation. SustaiN provides more flexibility with the timing of application as research shows that, on average, SustaiN reduces volatilisation by 50%.
PhaSedN (which contains SustaiN) is a popular autumn option for farms that require sulphur as well as nitrogen. PhaSedN contains fine-ground elemental Sulphur which, unlike soluble sulphate, will not leach over winter. As soil temperatures rise again in spring, soil bacteria becomes more active and as a result, will oxidise the elemental sulphur to sulphate sulphur, so that it becomes available to growing pasture.
Applications of around 30-40 kilograms of nitrogen per hectare are recommended in autumn.This could be supplied through 120-160kg of PhaSedN or 65-86kg of SustaiN per hectare with the typical response rate being between 5-10kg DM per kg in nitrogen applied. As with any nitrogen application, it takes time to grow the grass. Ideally, allow four to six weeks after application before assessing the overall effect for grazing the pasture.
Jim Risk
Nutrient Dynamics Specialist
Balance Agri-Nutrients
