Frequently Asked Questions
Frequently asked questions (FAQs) in relation to the National Variety Trials (NVT) program.
What is the NVT?
The National Variety Trials (NVT) program is the largest independent grain crop variety evaluation program in the world, generating credible information for growers and agronomists to assist in variety choice.
It is a national program established and conducted by the Grains Research and Development Corporation (GRDC) and includes both advanced breeding lines and commercially available grain varieties.
NVT’s main purpose is to create enduring profitability for Australian grain growers by providing growers and their advisers with comparative information on yield performance, grain quality and disease resistance ratings of commercially available grain varieties.
This information is independent, consistent, timely and accurate to assist in varietal decision making.
NVT is funded and managed by GRDC.
The NVT management team consists of seven GRDC staff responsible for the governance, operation, and administration of the program. The teams primary focus is the governance of the program and its successful delivery and continuous improvement.
All NVT services are contracted to service providers who perform the work on behalf of GRDC. Services include:
- field trial provision
- pathology testing
- statistical analysis
- grain quality testing
- results publication
- database management.
What varieties are included in trials?
For commercially available varieties: All relevant commercially available grain varieties are included in the NVT program. Relevance is determined using information on the uptake of varieties, delivery percentages within the region and on feedback from NVT Advisory Committees and NVT Participating Breeders.
Additionally, advanced breeding lines that will be available to growers soon are entered in the NVT program by breeding programs.
Growers need NVT information on varieties at the time of commercial release to assist in variety choice. As such, GRDC includes varieties that are close to commercial release to ensure at least one year of independent data before it is available to growers.
Between 2012-2021 the NVT program was wholly funded by GRDC, however, available spots were limited by the available budget, and demand from breeders to enter more pre-commercial entries outweighed availability. During this period only 22% of those pre-commercial entries were released to growers, NVT data on the remaining 78% were not commercialised.
Since 2022 a new model was implemented to allow breeders to leverage from GRDC’s investment in NVT, while addressing the issues outlined above. GRDC continued to cover the costs of testing all commercial varieties and testing of advanced breeder lines that are successfully released. At the same time, breeders became responsible for the marginal cost to test breeding lines that do not get released.
Independence and equitable access for all breeders will be unaffected by this model.
How are the trials managed?
Disease control/fungicide application is a common practice for growers. Removing the impact of pests and disease in NVT allows variety performance to be accurately measured without variation caused by differences in variety disease/pest resistance/susceptibility.
NVT trials contain a range of maturities, therefore multiple fungicide applications may be required to adequately protect all varieties trialled. The NVT program runs an additional pathology program that produces the NVT Variety Disease Resistance Ratings.
NVT trials are managed to minimise the impact of disease on varietal performance, in high disease pressure seasons a certain level of disease occurrence is unavoidable.
Susceptible varieties do suffer in a high disease pressure season, but if a trial had appropriate fungicide application at appropriate times, then the trial results are released. It is important to publish yield information in such disease prone years, as it is reflective of the real-world grower experience in those seasons.
Trial sowing windows must match district practice for each particular wheat trial series. Varieties in NVT are nominated to suit mandated sowing windows for the trial series, e.g., long season trials (very early sown) versus early season trials (early sown); versus main season trials (regular sowing date).
Sowing outside the relevant sowing window for a particular trial series will compromise the varieties performance and result in invalid data not suited to inclusion in the MET. A failed trial is not a good investment.
In the event of a late break, an early sown trial may require supplementary watering to ensure germination within the appropriate period to suit varieties sown. In this scenario, an early sown trial will hold no value without supplementary watering as it would just become a duplication of the main season trial or be abandoned prior to sowing.
Supplementary watering of trials may also be considered to ensure trials survive where severe post-emergent drought is threatening plant survival. A failed trial is a poor investment.
To provide transparency and accuracy in interpreting results, irrigation volumes are reported with the rainfall data.
It is recognised at a given location, the conditions between seasons change considerably, and we never expect the conditions experienced in one year will occur in following years.
The purpose of NVT is to provide information to growers that assists in varietal choice for their location. Due to the variation between years, this choice should not be based on a single year’s conditions; rather, performance of a variety in a location over time provides greater accuracy on future performance at that location.
It is recognised that pre-watering does create conditions that are different to those experienced in that location in that year. However, given the variation between seasons of the naturally occurring conditions, it is considered that avoiding trial failure (as described in the above question) and still producing valuable data for variety selection is the best use of resources.
It is important to note that the supplementary watering is measured, recorded and available in NVT reporting to accurately reflect the environmental conditions the trial was subjected to.
As NVT trials are managed, accurate variety comparisons in the absence of external limitations, nutrition should not be limiting, and fertiliser rates may exceed common commercial practice.
Fertiliser rates are calculated using nitrogen budgets considering soil fertility, moisture and yield potential, and are adjusted to suit each trial’s needs. All trial sites are comprehensively soil tested up to one metre depth prior to sowing, which aids fertiliser application decisions.
The NVT protocols do allow Trial Service Providers (TSP) the option for dry sowing under certain conditions:
- Germinating rainfall is imminent
- It is common district practice
- Growers in the region are dry sowing in that particular year
- Soil type is conducive to uniform establishment.
Dry sown trials may not receive timely and effective germinating rains to enable the trial to germinate within its optimal sowing window. Additionally, dry sown trials have an increased risk of staggered emergence leading to patchy establishment. Trials with patchy establishment have a high chance of being compromised due to plot variability and an increased abandonment risk.
Crops which have varieties spanning a wide range of maturity and potential sowing dates are separated into several trial series (groups) based on variety maturity:
- low-medium rainfall zone (early series)
- medium-high rainfall zone (mid series).
- wheat and barley
- long series trials (very early sown)
- early series trials (early sown)
- main series trials (regular sowing date).
Separate trials for crops based on maturity range allow for more appropriate sowing dates and in-season management for the entries targeting that trial.
Acceptable sowing windows are clearly defined for all trials within a crop and region. Varieties included in trials are nominated based on their maturity to fit within sowing windows to avoid frosting and other issues that can impact if varieties are not suitable for the sowing windows.
Sowing windows are constantly reviewed in light of district practice. Over the 15 years of NVT running these have advanced significantly with most main season trials now sown 3-4 weeks ahead of those sown 15 years ago.
Trials are sown at dates to represent district practice and trial managers generally aim to sow at the same time as the grower for the paddock used or within days to avoid the complications of emerging crops and subsequent chemical drift issues etc.
Differences in seed size, seed origin/source and seed nutrient content affect yield performance which can obscure variety performance.
In order to remove these variables from the program, each year NVT produces premium quality seed for over 180 varieties at a single location, which is graded to ensure uniformity. Genetic testing and periodical renewal of seed occurs to ensure varietal purity and avoid contamination.
Seed for all commercial lines are produced; except hybrids (canola and sorghum) which require specialised production systems which are managed by breeding programs.
Where are the trials located?
Trial locations are chosen following extensive consultation with stakeholder groups including:
- NVT Advisory Committees (NAC)
- GRDC regional grower panellists
- NVT Participating Breeders
- market production intelligence.
Key considerations in trial distribution include:
- Representation and prevalence of existing crops
- Representation of environments within a region
- Avoidance of clustering of trials resulting in duplication and obsolete trials.
NVT’s site selection aims to ensure adequate representation of all environments and conditions for established crop species within regions. Regions with large uniform environments covering vast areas may have a smaller NVT density compared to regions with less uniform environments.
To make best use of resources, the NVT program is careful to avoid clustering of trials in locations where environments are similar resulting in data that does not provide additional value to the data set.
NVT is used for assessing varietal differences between varieties/lines in established cropping regions of that crop or maturity. The distribution of trials is designed to reflect local crop presence.
NVT is not used as a demonstration program to encourage uptake of new crop types or maturities. There are other potential GRDC investments that are suited to this purpose.
Representation of crop types in NVT in a region broadly correlates to the popularity of those crop types in the region. NVT trials are not feasible in areas where there are few variety options available and agronomic crop practices are not well established.
Site uniformity is key to good trials and detecting useful differences between varieties in NVT. As such, site selection is based on uniformity and ability to deliver a consistent trial across all plots.
Trials with soil variability produce variable data which obscures any variety yield differences, resulting in trial failure which is not a good investment. As such, areas with shallow rocky outcrops, tree lines, water courses, variable compaction, salinity issues, toxicity/deficiencies, etc. are avoided as these factors would cause undesirable non-genetic variation between plots.
Low, medium and high yielding environments are all included in NVT which has locations all around the country to best represent the full range of conditions growers experience.
The NVT is not a yield potential trial, but a variety comparison trial. Trials are located in paddocks with a soil type widely representative of the district and region.
Best soils are not selected but rather, site selection is based on soil uniformity and ability to deliver a consistent trial across all plots. NVT includes enough trials in all environment types to provide accurate variety performance data for all environments.
Trials can move between neighbouring properties from year-to-year provided the trial is within a 25-kilometre radius of the locality (allocated site name). A consistent location over several years allows more accurate comparison of varieties across years and increases the reliability of the MET analysis.
Trials are more likely to be successful if retained on one representative property, due to factors such as: pre-trial planning issues, reliable and well understood trial manager/property owner relationships.
Different crop rotations are required for optimal performance of various crops, NVT is designed to show genetic comparison not limited by external factors, such as rotation.
Pest management becomes extremely difficult where different crop types are sown in close proximity and potential herbicide drift can also be a major concern.
Crop profitability is best determined from trials specifically designed and managed to achieve this goal. Again, comparison between trials at one location is not statistically valid.
For more information, see Trial results question: 'Should we compare variety performance across different trials (e.g., canola herbicide groups, or between species)?
You can use your knowledge on equivalent grain production environments (regionally or even nationally) to your situation to select remote trials which may be relevant to your environmental situation.
Alternatively, NVT’s online trial results map - allows you to see where all trials are located and select those most relevant or nearest to your location.
Multi Environment Trial: The Multi Environment Trial (MET) analysis is very useful for predictive purposes. It produces the most accurate and reliable prediction of future variety performance. MET analysis results are presented at an individual trial level but with the robustness of a massive dataset.
The MET analysis is conducted on a five-year dataset and includes trials from multiple environments. For some varieties, the analysis is conducted on more than 660 plots to gain an accurate and reliable result.
The strength of the MET analysis is that it analyses trials from a wide range of seasonal and environmental conditions. This ensures varieties are identified to enable selection of consistently high performing varieties for a given location.
Single Site Analysis: The Single Site Analysis (SSA) is very useful for descriptive purposes. It is less accurate and less reliable than the MET analysis for predictive performance, but provides a good description of performance in that trial for the particular season. The data is available soon after a trial is harvested.
The SSA is conducted on a single trial at a single location in a given year, e.g., 2019 Horsham wheat. The analysis is conducted on a limited dataset, usually three plots for each variety.
The SSA is descriptive of the environmental conditions at that trial, e.g., how the varieties performed with an early break or dry spring.
The weakness of the SSA is that it has a low reliability to be able to repeat its results, i.e., if the environmental conditions changed so would the variety rankings.
Single Site Analysis: Many steps occur following the harvest of a trial, including data upload to the database, data analysis by biometricians, data review by breeders and NVT management prior to general public release.
This process ensures the data achieves the high standards in NVT protocols. Each step provides a period of review or enactment, and this results in a minimum of 10 days between day of harvest and public release of results. The average tie for the release of single site analysis of a trial is 14 days.
Multi Environment Trial: MET analyses cannot commence until all trials within the dataset have been harvested and undergone single site analysis. Not all trials in a particular dataset are harvested at the same time.
MET analyses are reviewed by NVT management and other stakeholders for accuracy prior to public release. These analyses generally occur during late December through to late January before release on the NVT website.
NVT have a vast network or trials covering all major grain crops and all grain producing environments in Australia. NVT’s online trial results map allows you to see where all trials are located.
You can use your knowledge on equivalent grain production environments (regionally or even nationally) to your situation to select remote trials which may be relevant to your environmental situation.
It is statistically not valid to compare results between trials even if co-located. This is because different trials at a location are:
- Spatially separated creating increased site variability
- Managed differently according to the herbicide system, maturity group, and species, e.g., canola herbicide tolerance trials, bread wheat vs durum wheat trials, barley vs wheat.
- Statistically managed as separate experiments, including in their design and analysis.
The NVT program is a completely independent program funded and managed by GRDC to provide growers with reliable information to assist in variety choice. All strategic, operational, and management decisions are made by GRDC to ensure the best outcome for the Australian grains industry and Australian growers.
Collaboration between the NVT and Plant Breeding Programs is integral to the success of NVT, this collaboration provides NVT with:
- Ability to produce independent information on the latest release commercial varieties through NVT early access to pre-commercial breeder lines
- Valuable real-time feedback on trial quality to assist in monitoring the nationwide trial program
- Expert knowledge and experience on varietal performance so NVT management can assess the credibility of trials and trial results prior to general publication.
Plant breeders or their associates do not decide on the release of trials to the public, but their views are one of many considered by NVT management. NVT management welcomes feedback and any queries about the integrity of a trial which instigates an independent investigation by the NVT team.
Each NVT trial series is only sown at one time of sowing. Therefore, varieties in the NVT will vary in flowering date, maturity etc., making it difficult to separate the confounding effects of stage of development and timing of the compromising event, for example, frost/shattering/pre-harvest sprouting etc.
Agronomic data suitable for comparison between varieties should be collected from trials designed to specifically capture that data without bias.
To accurately compare performance between varieties, NVT trials only have a single time of sowing for all varieties.
Frost events are random and will coincide with different growth stages for different varieties sown at the same time. Frosts will have differing levels of impact on yield and quality dependent on maturity of variety at the time of the frost event.
If varieties are frosted, comparative yield performance measurements are inaccurate for predicting variety performance, which is the purpose of NVT. Frosted trial information does not add value to the long-term Multi Environment Trial (MET) data set and could potentially prejudice results. The information is therefore ‘quarantined’ to protect the larger NVT data set.
Frosted trial results are reported in the ‘Quarantine Trial Reports’ published on the NVT website for transparency and for local growers. However, these results should not be relied on to make variety choice decisions. Information from frosted NVT trials is not a representation of varietal frost tolerance due to the differing maturity stages of varieties when a frost event occurs.
Quarantining of results occurs for any adverse events that affect trials resulting in comparative varietal performance being biased (terminal heat stress, livestock damage, etc)
NVT recognises stressed trials can provide valuable insights into variety performance, and invests time, money, and resources to extract maximum value from trials affected by stresses (e.g. heat, drought, waterlogging, wind damage, frost etc).
When stress has occurred at a trial, the trial managers assess and score any effects on plots. The statisticians will assess these measurements to determine their significance in improving variety performance in the analysis.
Only trials that are so poor that they can't be used to adequately compare genetics are not released, however, information on these trials can be found in the quarantined trial results.