Good morning,
I had a field trail with 800 genotypes and two different nitrogen treatments. The problem is that the block with the lower nitrogen fertilization was sown 4 weeks after the first block and I looked for developmental traits, like the timepoint of heading and if there is a difference between the two nitrogen treatments.
How can I consider this different sowing dates in my ANOVA, to check if the differneces are caused by fertilization or timepoint of sowing?
Thanks in advance,
Laura
Consider the sowing date as a factor, as well as the genotypes and nitrogen treatments.
You may use split-split plot design or factorial randomized design taking sowing date as a variable. Since late sowing was in a block the former design would be most appropriate. As you mentioned in your question that you are looking for developmental trait, weather data need to be collected and those may also be used in interpreting your data.
In your description, the nitrogen and planting date treatments are fully confounded. There is no way to distinguish between them in this data set. The 800 genotypes have been evaluated in two environments, which gives you considerable information on the stability of the traits you measured. However, comparisons between the nitrogen treatments are not possible.
With field experiments like this, it is often helpful to run the experimental design through ANOVA using mock data before planting the trial. That test often results in changes to the experimental design.
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