Forages for Reduced Nitrate Leaching

What was the FRNL programme?

The DairyNZ-led programme Forages for Reduced Nitrate Leaching – a cross-sector approach (2013-2019) provided new scientific knowledge, tools and technologies for forage production that can amount to more than 20% reduction of nitrate leaching from dairy, arable, sheep and beef and mixed-farming systems.

Project status: completed

How forages can reduce nitrate leaching

A urine patch is the primary source of nitrogen (N) leaching in grazed pasture and crop. Forages can reduce nitrate leaching by:

• reducing the amount of N in the diet, which reduces the amount of N excreted in urine
• reducing the N concentration of the urine, improving the utilisation of this N
• increasing plant N uptake from the soil before it drains away, by greater growth in the cool high-drainage season or by deeper root systems.

Key programme results

1. Some pasture species, such as plantain and Italian ryegrass, can reduce nitrogen concentration of urine from animals and improve plant nitrogen uptake in the cooler season.
2. Low nitrogen, high quality feed crops, such as fodder beet, maize and cereals, reduce urinary nitrogen excretion by animals.
3. Catch crops, such as oats, reduce nitrate leaching when established early in the winter season, through the uptake of water and nitrogen. These crops also provide additional feed and may increase total annual dry matter production.

What we did

The Forages for Reduced Nitrate Leaching programme combined the expertise and resources of these monitor farms and three Crown Research Institutes (AgResearch, Plant & Food Research, Manaaki Whenua - Landcare Research), one university (Lincoln University), and two industry-good bodies (DairyNZ and the Foundation for Arable Research). The main funder of the programme was the Ministry of Business, Innovation and Employment (MBIE) with the six programme partners providing co-funding.

FRNL used a range of field trials, lysimeter studies and animal trials to define viable options. Collaboration with commercial farms, the FRNL monitor farms, ensured their applicability and adoptability. The farmers provided feedback throughout the programme, and research questions and experiments were adjusted accordingly. This flexibility in the programme proved to be a critical factor for its success.

The FRNL monitor farmers tested and demonstrated the researched mitigation options on farm. The use of plantain, fodder beet and catch crops did not appear to impact negatively on feed supply and farm profit. Modelling the farm systems showed year-to-year variation in nitrate leaching, and for some farms substantial improvements since the start of the programme. The monitor farmers’ questions and feedback directed the development of information to support implementing these options on farm.

FRNL and Overseer model

The Forages for Reduced Nitrate Leaching (FRNL) programme identified early on that having the effects of mitigation options reflected in the Overseer model would be an important outcome of the programme.

Led by AgResearch, research results were collated and proposals for model changes were made*. With the recent update of Overseer, the model will now reflect the effects of plantain’s plant composition on urine nitrogen excretion: less of the excreted nitrogen ends up in urine and urine patches have a lower nitrogen load due to a greater urine volume per animal per day. Depending on the proportion of plantain in the animals’ diet, this will reduce the N leached.

Further research underway

Further research on soil processes is underway in the Plantain Potency and Practice programme and may in the future result in further updates of the model to also reflect those effects. FRNL used the cultivar ‘Ceres Tonic’ in the various experiments. Other work suggested similar effects of ‘Agritonic’ but that differences between cultivars exist. More information can also be found on the Plantain page.

In some regions, farmers will need to report their Overseer nitrogen leaching number to regulators. These regulators will have their own requirements for providing evidence or auditing farm management. The choice of plantain cultivar may be one aspect these regulators will want to verify. Additionally, the percentage of plantain in the pasture will need to be entered in Overseer. DairyNZ developed an easy-to-use approach to assess plantain content.

Hover over the map below and click on the hotspots for more information on the monitor farms.

Inside Dairy and Technical Series articles

The following reports document the process to determine the required changes in the Overseer model, to reflect the plantain effect on reducing nitrogen leaching: