Get the most from your nitrogen

Efficient use of nitrogen (N) fertiliser can increase productivity and profitability and reduce risks to the environment, while helping you meet N cap rules.

Using both N surplus and N conversion efficiency (NCE) metrics to improve on-farm performance can help achieve a balanced approach to N management, resulting in productivity gains, economic viability and long term sustainability. Nitrogen surplus indicates N losses, while NCE provides insight into the effectiveness of N use in production.

Nitrogen surplus is the difference between N inputs (N brought onto the farm as fertiliser and supplements) and N outputs (N removed in products), measured as kg/ha/yr, with a smaller number being desirable.

Nitrogen conversion efficiency, on the other hand, describes the proportion of N fertiliser that is converted into product.

It is calculated by dividing the sum of products by the sum of inputs, and is expressed as a percentage, with a higher number reflecting a better performance.

The 4Rs of good fertiliser management

Following the ‘4 Rs’ of good fertiliser management can help to increase both NCE and decrease N surplus.

Right rate

The rate of N fertiliser applied depends on its purpose. For example is it to fill a feed deficit, or to push as much growth as possible?

Right time

Factors such as soil temperature and soil moisture can lower the pasture response (kg DM per kg N/ha applied). Fertiliser should be applied when the round length is not faster than the number of days needed for significant pasture response, and pasture should be consistently grazed at the 2.5- to three-leaf stage. See Table 1 for how pasture growth rate impacts N fertiliser response.

Table 1: Impact of pasture growth rate on response rates to N fertiliser (N applied at optimum rates)

Right place

Fertiliser should be placed where it can be most efficiently used. Spreadmark certified spreader operators are trained to spread fertiliser accurately, and use certified spreading machinery to apply fertiliser at an even rate and distribution pattern, exactly where it is needed.

Right product

Applying N in the right place at the right time can reduce leaching losses, but up to 42% of the total N applied can still be lost via volatilisation in pastoral situations, with losses typically between 10% and 20%¹.

Using a fertiliser coated with a urease inhibitor, such as SustaiN, helps to minimise N lost as ammonia gas, and keep more in the ground for plant use and increased pasture production. Compared to standard urea, SustaiN’s AGROTAIN^® coating cuts N volatilisation losses by around 50%² and increases N efficiency, with research showing over a wide range of conditions the average increase in pasture yield is 5%³.

SustaiN can also be applied at any time of year when a crop or pasture needs N, without the need for sufficient rainfall within eight hours to reduce volatilisation losses.

Soil and herbage testing checks if levels of other macro- and micronutrients are optimal and not limiting growth. According to the Law of the Minimum, plant growth is constrained by the level of the scarcest nutrient, so ensuring other nutrients are not limiting growth gives you the best bang for your buck. Spring maintenance fertiliser or a blended mix such as SustaiN + K to push quality feed into summer can be helpful in achieving this.

¹ Theobald PW, Ball PR 1984. Nitrogen lost by ammonia volatilisation, and the effectiveness of urea and ammonium sulphate fertilisers, Proc. NZ Grassland Assoc. 45: 236-8.

² Zaman M, Saggar S, Stafford AD 2013. Mitigation of ammonia losses from urea applied to a pastoral system: The effect of nBTPT and timing and amount of irrigation. Proceedings of the New Zealand Grassland Association 75: 209-214.

³ Stafford A, Catto W, Morton JD 2008. Ballance Agri-Nutrients approach to sustainable fertiliser use. Fertiliser and Lime Research Centre, Massey University, Occasional Report No. 21: 197-205.