Plantain research

Plantain has been in the spotlight as scientists and farmers investigate its usefulness as pasture feed and its potential environmental benefits.

Plantain has been part of Aotearoa New Zealand pastures for a long time, but plant breeders have created new cultivars that are both more nutritious and palatable for dairy cows. The initial research focused on plantain’s effect on milk production and pasture management practices. Scientists found that dairy cows produced the same or increased amounts of milk. The trials also provided information on how to establish and maintain plantain as part of an existing sward or as a special-purpose crop.

Reduced nitrogen concentrations

Scientists also noted that plantain has additional properties of interest. Cows that consume plantain have reduced levels of nitrogen in their urine. This is due to lower nitrogen content in plantain (compared to other forage plants) and plantain’s possible diuretic properties – cows urinate more often so the nitrogen in urine patches is less concentrated.

Reducing nitrogen in urine patches is important. Industry group DairyNZ recommends using 50 kg N/ha of nitrogen fertiliser or less per single application to minimise nitrogen leaching to waterways. Urine patches can contain up to 700 kg/N/ha on average for a ryegrass and clover diet. This rate exceeds what the plants can use, so surplus nitrogen can leach below the root zone and enter groundwater and then surface water and create environmental issues.

Early results during trials show that using alternative forages like plantain can reduce the nitrogen concentration of urine by 25% and reduce nitrate leaching under urine patches by 30–60%.

Plantain pasture samples

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DairyNZ conducts trials on research farms, which allow scientists to test ideas in real-world conditions. Collecting pasture samples helps researchers determine the percentage of plantain growing in the paddock.

Rights: DairyNZ

Reducing greenhouse gas emissions

Microbial processes within soils such as denitrification convert nitrogen to other forms, including nitrous oxide (N2O) – a long-lived greenhouse gas. Nitrous oxide accounts for around 12% of Aotearoa New Zealand’s greenhouse gas emissions. The country’s N2O emissions rates have nearly doubled since 1990.

Scientists think that plantain might help to reduce N2O emissions. Plantain reduces the amount of nitrogen entering the soil via urine patches so surplus nitrogen is reduced. A second area of research involves compounds the plants release into the soil. Scientists think these compounds are natural nitrification inhibitors – they reduce nitrogen mineralisation and nitrification. The research is ongoing.

Plantain may also help reduce another greenhouse gas – methane. Methane is produced in the rumen of cows and is released by burping. As with nitrous oxide emissions, early research results are tentative;

Methane monitoring with a GreenFeed unit

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The GreenFeed unit measures the emissions of methane and CO2 exhaled and burped by cows when they visit a feeding hood. DairyNZ scientists use the data generated by the unit to measure whether plantain will help to reduce methane emissions from dairy cows.

Rights: DairyNZ and The University of Waikato Te Whare Wānanga o Waikato

Moving from research sites to on-farm sites

The key part of agricultural science is ensuring the research is grounded in on-farm practice – that’s farm system science.

Kieran McCahon, Solutions and Development Specialist, DairyNZ

Many questions yet to answer

Even though researchers are building their knowledge about plantain, there are still a lot of questions:

• Does plantain have diuretic properties or do cows simply urinate more because plantain has a higher water content than other feeds?

• Do smaller urine patches created more often affect N2O emissions?

• What biological mechanisms are responsible for reduced N2O emissions?

• Does the plant structure affect N2O emissions?

• Plantain does not affect milk production, but might there be changes to milk properties that impact manufacturing processes?

• Do seasonal patterns have an impact on the results?

DairyNZ

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DairyNZ is the industry organisation that represents all New Zealand dairy farmers. DairyNZ supports farmers through investing in research, resource development, extension and advocacy to ensure sustainable dairy farming and food production.

Rights: DairyNZ