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
- 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.
- Low nitrogen, high quality feed crops, such as fodder beet, maize and cereals, reduce urinary nitrogen excretion by animals.
- 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.
Diverse pasture, low-N crops and catch crops appeared to be practical options in many situations and were readily implemented on farm. Collaboration with Overseer ensures that these options will be reflected by the model, so that farmers can assess the benefits in their specific situation and how to adjust management to optimise their use. For the FRNL monitor farms, success of reducing modelled nitrate leaching varied, depending on what the farm was already doing, concurrent changes in management, soil type and climate.
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.
Hover over the map below and click on the hotspots for more information on the monitor farms.
Identifying research priorities for establishing plantain on-farm
A modelling exercise was carried out to establish the drivers of cost when establishing plantain to achieve 20, 25 and 30% in pastures on farm. This showed that the most important factors were the percentage of plantain that can be established in an existing sward and the cost of doing so (e.g. broadcast, drill). Secondly, the percentage of plantain establishing in new pastures and the persistency of plantain were also important factors.
Inside Dairy and Technical Series articles
The power of combining field trials and modelling (Technical Series December 2019)
Tactical use of nitrogen fertiliser (Technical Series December 2019)
Farming for a lower footprint – what should we focus on? (Technical Series September 2019)
Plantain helping farmers to achieve environmental targets (Technical Series April 2019)
N surplus shows performance (Technical Series April 2019)
Grassroots science holds key to sustainable farming (Inside Dairy July 2018)
Waikato research reveals benefits of using catch crops (Inside Dairy June 2018)
Getting plantain into your system (Technical Series June 2018)
Grazing systems and less N leaching: plantain trials look promising (April 2018)
Fodder Beet: Friend of foe? (Technical Series March 2018)
Science puts couple on the front foot (Inside Dairy October 2017)
Best irrigation practice saves water and grows more (Technical Series October 2017)
Meeting nitrogen leaching reductions while retaining a profitable system - a Selwyn catchment example (Technical Series October 2017)
Unbeatable crop? Managing fodder beet's benefits and risks (Inside Dairy September 2017)
Pasture species mixtures to reduce nitrogen leaching (Technical Series June 2017)
Catch crops for production and environmental benefits (Technical Series March 2017)
Making gains through research (Inside Dairy March 2017)
Focus on forages to reduce urine patch N leaching (Technical Series December 2016)
Two wins from using a catch crop (Inside Dairy November 2016)
Joint effort targets nitrogen leaching (Inside Dairy November 2015)
Forage systems to reduce nitrate leaching - Regional research (Technical Series November 2014)
Forage systems to reduce nitrate leaching (Technical Series October 2014)
Forages for Reduced Nitrate Leaching is a DairyNZ-led collaborative research programme that combines the expertise and resources of DairyNZ, AgResearch, Plant and Food Research, Lincoln University, Foundation for Arable Research and Landcare Research.