I am working on an experiment where I will be growing soybean in pots through all its stages in a greenhouse, I have a total of 65 plants in the beginning with 4 treatments and 1 control group making a total of 13 plants/replications per treatment. Mid-way through the experiment I will be taking 3 random samples from each group, a total of 15 plants, and removing them from the soil to look at nodule count and total plant biomass.
The experiment design that I have set up for pot placement in the greenhouse was done as a randomised complete block design with 13 blocks and 5 rows/treatments, my question is how do I take these 15 random samples from the experiment without destroying blocks and thereby making it impossible to do the statistical analysis that I plan to do? The reason for the design is to account for spatial variation in the greenhouse such as light exposure.
The figures I have made are my two suggestions for how I could do this. In figure 1 I show the design and placement of the pots, each letter A-E is one treatment (randomly assigned to a pot number for each block) and the numbers are the numbers that were assigned to those pots. In figure 2 I remove 3 randomly assigned full blocks from the experiment for destructive samples, and in figure 3 I took 3 random samples from each of the treatment groups independently and removed them.
I feel as if removing complete blocks like in figure 2 would be the best option, because then I would not be affecting the other blocks as happens in figure 3, the disadvantage of this option is that the samples are less spread and it would perhaps not account too well for variability in the greenhouse for the destructive samples, but do well for the non-destructive ones.
Figure 3 probably does well in accounting for spatial variability in the destructive samples, but it will be destroying the blocks for the finished plants and therefore it seems to me like it would not be possible to do a proper statistical analysis on the finished samples of which I care most about.
How can I solve this? I would also appreciate a suggestion on how to analyse these results if it is possible. Is there any other way I could take destructive samples like this without ruining it? I feel like growing the destructive samples separate from the main group in the greenhouse (but close to each other) would not account enough for variability.
My supervisors have said that taking the destructive samples will not affect the growth of the surrounding plants as long as I remove the pots and not clip the plants.
Eirik Lågeide I think you might have it solved already " I feel like growing the destructive samples separate from the main group in the greenhouse (but close to each other) would not account enough for variability. " like you said it.
Out of 13 plants per replication you must be taking 5plants to biometrical reading remaing plants you can use for destructive sampling
Rajesh S Patil Well, my concern about doing that is that they will not be comparable to the main group because they are separated from the main group and therefore the spatial variability will not be the same, since they're localized in f.ex a more light intense area of the greenhouse, making me unable to identify if it's the treatment affecting the nodule-formation or the growth conditions. The whole point of the destructive midway samples is to see if the plants have properly formed nodules in at least the control group, and to possibly also look at a generalised range of nodule count in the treatment groups during vegetative growth.
Nataraj S K what do you mean about biometrical readings? Why do I need 5? I have concluded that I need to grow at minimum 10 plants until they produce seeds for a proper robust statistical analysis for my main results, and that 3 of each treatment is enough to give me a yes/no answer on nodule forming. I don't quite understand what you mean.
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