Finish the season with nitrogen

Finish the season with nitrogen

1 April 2017

Make the most of your last chance to get pasture in good shape for spring. That’s the advice from Ballance Nutrient Dynamics Specialist, Jim Risk.

“Your pasture’s form at the end of this season determines how well it will respond in the next,” says Jim.

“The impact of summer and the need to get stock in good condition before winter may have taken a toll on your pasture covers. Address that now and pasture will be primed to deliver good levels of feed in spring when it is most needed.”

Depending on your stocking rate and rotation length, a pre-grazing cover of around 2500-3000 kilograms (kg) dry matter (DM) per hectare (ha) is a good target going into winter. “If you are shy of this goal, autumn growing conditions plus the growth-boosting power of nitrogen (N) can help you get there,” says Jim.

Which N is best?

With many nitrogen fertiliser options now available, 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.

“It helps to review what does – or doesn’t – influence this process and the effectiveness of nitrogen to help decide which product is your best investment,” says Jim.

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.1

Grass growth is temperature dependent, which is why recommendations suggest that soil temperatures should be consistently above six degrees Celsius (°C) at 9am before you apply nitrogen. This is often more common in autumn than in late winter/early spring, so a positive pasture response to autumn-applied nitrogen is likely.

Soil moisture: This is critical. You need between five to 10 millimetres (mm) of rain or irrigation within eight hours of application to minimise volatilisation losses. Rainfall or dew before application will not prevent losses.

Autumn rainfall can be fickle and irrigation is not always practical, so it makes sense to protect your nitrogen investment by using a product from the SustaiN range. The urea in SustaiN is coated with a nitrogen stabiliser that reduces the action of urease enzymes in the soil. This slows down the conversion of urea to ammonium, which in turn lessens volatilisation. “SustaiN gives you more flexibility with the timing of application. Research shows that on average, SustaiN reduces volatilisation by 50 percent,” says Jim.2

PhaSedN, which contains SustaiN, is a popular autumn option for dairy farms that require sulphur at this time of year. PhaSedN contains fine-ground elemental sulphur, which will not leach over winter, unlike soluble sulphate. As soil temperatures rise in spring, soil bacteria become more active and start oxidising the elemental sulphur to sulphate sulphur, so it becomes available to growing pasture.

Applications of around 30-40 kg of nitrogen per hectare are recommended in autumn; this could be supplied by 120-160 kg of PhaSedN or 65-86 kg of SustaiN per hectare. The response rate will typically be from five to 10 kg DM per kg nitrogen applied. As with any nitrogen application, it takes time to grow the grass, so ideally allow four to six weeks after application before assessing the effect or grazing the pasture.

For advice on your autumn fertiliser application talk to your local Fonterra Farm Source TSR or Ballance Nutrient Specialist today.

Article supplied by Ballance Agri-Nutrients

1For example, Black et al, (1985), New Zealand Journal of Agricultural Research, 28: 469-74

2Zaman et al, (2013), Proceedings of the New Zealand Grassland Association, 75: 209-14