The Plantain Evaluation System assesses the effectiveness of plantain cultivars for reducing nitrate leaching. The aim is to provide farmers and regulators with confidence in the performance of cultivars classed as Effective at reducing N leaching and enable continuous improvement of cultivars used for environmental purposes.
What is the basis of the Evaluation System?
Certified Tonic and Agritonic plantain cultivars have been shown to be Effective based on an independent assessment of published data (prior to the establishment of the Evaluation System) showing their ability to reduce N leaching, driven by reduced urinary nitrogen concentration and total nitrogen excreted per day in lactating cows. Tonic plantain is an ageing cultivar and is no longer commercially available. Agritonic is therefore used as the benchmark cultivar in the Evaluation System.
See Environmental Benefits of Plantain page for details of the scientific evidence of reducing N leaching using Certified Tonic and Agrictonic plantain cultivars and evidence of differences between cultivars.
How are cultivars assessed in the Evaluation System?
The Evaluation System is currently set up to assess the effectiveness of cultivars for achieving:
- Increased urine volume/day (dilution effect)
- Reduced urinary nitrogen excreted/day (partitioning effect)
These measures are predictors of impact on N leaching.
DairyNZ has developed a testing protocol that seed companies can use to assess the effectiveness of their cultivars for these N cycling effects. Cultivars are assessed against a positive (benchmark) control (Agritonic plantain) and a negative control (perennial ryegrass). Statistical analysis is used to determine whether the test cultivar is as effective as the benchmark.
The research and results of trials are reviewed by the Evaluation System Assessment Group. The group includes members from DairyNZ, Massey University, Manaaki Whenua Landcare Research, Plant & Food Research, and PGG Wrightson Seeds.
Cultivars that are not significantly lower performing than the Benchmark are classed as Effective.
Effective cultivars (July 2022)
The following cultivars are classed as Effective by the Evaluation System Assessment Group.
- Ceres Tonic
Note: Ceres Tonic and Agritonic cultivars are marketed by PGG Wrightson Seeds as a blended product, EcotainTM. Certified Ceres Tonic is no longer available outside of EcotainTM
In all cases, certified seed must be used. See our Seed Selection page for further details.
Science currently underway
The current protocol requires measurement of plantain, ryegrass and N intake and dung/urine/milk N excretion using a metabolism stall facility. This is expensive and facilities are limited.
Research is now underway as part of the Plantain Potency and Practice programme to understand the physical traits of plantain which drive reduced urinary nitrogen, and increased soil nitrogen retention. This will enable a plant-based testing method to be developed to assess the effectiveness of cultivars, and in turn, will enable faster improvement of cultivars to achieve reduced nitrate leaching.
By 2027, the system will also account for the effectiveness of cultivars for retaining nitrogen in the soil. By 2025, the system aims to use plant measurement instead of animal trials.
As we learn more about the mechanisms driving reduction in nitrate leaching, the relative effectiveness of the various cultivars in the Evaluation System may change.