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Trials with maximum value A series of FAQs can be found at NVT Online. Here, additional questions regularly posed to the NVT team, regional panel members and GRDC employees are explored To allow varieties to reach full potential, fertiliser inputs may be higher than those applied commercially. photo: Emma Leonard NVT structure and operation 6 By Tom Giles, Allan Bedggood and Alison Kelly Why are fertiliser rates applied to NVT trials often higher than those used in the district In NVT trials the objective is for all varieties to reach their water-limited yield potential (under the given management regime) to provide the best indication of performance. To achieve this, nutrition must not be limiting and so greater fertiliser rates than may be commercially viable can be applied. NVT trials should not be confused with gross margin trials. Why are the trials now treated with fungicide The objective of NVT is to provide data on the yield potential of a variety. Without disease control, variety rankings can be very different (Figure 1). Figure 1 shows varietal comparison from the 2010 NVT main-season wheat trial at Spring Ridge, New South Wales, with and without fungicide. Please note that error bars in Figure 1 indicate the maximum standard error deviation (SED) for any combination of varietal yields. If any two error bars overlap yield difference is not significant. Disease ratings for wheat, barley and blackleg in canola are now covered by separate, nationally coordinated screening projects (see pages 10 and 11). For pulse crops, disease rating remains part of the public breeding programs. NVT site mangers are instructed to control or prevent the predominant fungal infections experienced in the locality using commercially available fungicides. This applies to all crop types within the NVT. If the site was frosted or had a significant weed presence what happens to the data Where trials are harvested but temperature data from the site indicates they have been badly frosted the trial result is flagged as ‘invalid’ and not used in further analyses. Significant presence of weeds in a site, especially in patches of varying density, distorts relative varietal performances and the trial result is flagged as ‘invalid’ and not used in analyses. How can I arrange a visit to a NVT site At the NVT Online website (www. nvtonline.com.au) select the ‘Resources’ tab and the link to ‘Trial sites’. All NVT sites across Australia are listed by state. For each site the name and contact number of the trial manager are provided. Contact the trial manager for a ‘mud map’ and directions to the site. Trial managers can also provide the contact details of the farmer collaborator and indicate any access issues that may be associated with the site. Plot layouts are available at each site, usually located in a piece of white drainage pipe. A peg will indicate plot one. My closest site is more than 40 kilometres away, how should I use the NVT results Trial results from one site in one year are interesting but those conditions may never occur again. This is also true for how a
variety will yield on-farm – it varies from paddock to paddock and year to year. The NVT trial network exposes varieties to a range of growing environments experienced across multiple sites and seasons. The analysis of data across multiple environments gives a ranking of how varieties perform in a given environment and shows how stable this ranking is across other environment types. Growers and advisers are encouraged to look at long-term data across a range of sites that are applicable to their own situation, irrespective of the distance of these sites from their property. How can small plot trials be accurate enough to inform variety decisions at farm-scale A fair comparison of varieties can only be made when they are grown under the same conditions. This is especially difficult in large-scale plots due to the extent of variation in soil characteristics across the paddock. Small plot trials provide the best opportunity to test varieties under similar conditions as it minimises the effect of large-scale field variation. Small plot trials in combination with modern statistical methods have been well established as the most accurate way of performing variety evaluation. Most of the district was sown dry. Why were the NVT trials not dry-sown The biggest risk to dry seeding is a false break. Small amounts of rain may germinate the seed but then the soil dries out, causing the seedlings photo: Emma Leonard NVT site visits can be arranged by contacting the trial site manager. Details of the locations and contacts for all trials can be found at www.nvtonline.com.au to die. Often this happens to only part of the seed sown, with the remainder germinating following later rains. A trial with patchy establishment is useless for varietal yield comparison. In comparison, a patchy crop in a commercial paddock may allow plants to branch and compensate to achieve adequate yield. By mid-May, the likelihood of a false break is reduced; after this time trials may be sown dry. How are NVT site locations selected The location of NVT sites evolved from the state department of agriculture variety trials that were conducted prior to 2005. Trials are generally located in each of the production zones of a state although not on a pro-rata basis. As well as providing regional adaptation information, the NVT trial sites also form a hub for many grower discussion groups and this can drive the choice of location for some sites. However, as new statistical technologies come online, the ability to define and maintain the ‘must-have’ sites for the scientific evaluation of varieties will be greatly improved. This new analysis will provide greater flexibility for NVT sites to be located at grower group field day sites and other locations frequently visited by growers. □ GRDC Research Codes CAS00002, UW00006 More information: www.nvtonline.com.au 7 NVT structure and operation FIGURE 1 Varietal comparisons from the 2010 NVT main season wheat trial at Spring Ridge, NSW Yield (t/ha) 8 7 6 5 4 3 2 1 0 Sunstate Peake A Sprayed Lincoln A Orion A Dakota A Unsprayed EGA Bounty A Kennedy A Sunvale Janz Spitfire A EGA Wylie A Livingston A Ventura Error bars indicate the maximum SED for any combination of varietal yields. Consequently, a lack of overlap of any two error bars indicates a significant difference in yields. Ellison A Sunco Sunzell EGA Stampede A GBA Ruby A Sunvex A Lang A QAL2000 Chara A GBA Hunter A EGA Wills A Merinda A EGA Gregory A Crusader A Gladius A
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