What indices are there to see the effect of herbicidal weed management in field crops? I am more interested to know the indices for the experiments where weedy check and weed free treatments aren't kept (and the farmers' practice is control treatment).
Checks (controls) are needed to compare your findings to situations representing a realistic ideal situation. These realistic ideal situations (checks) are determined according to the aim of experimentation as follows::
1. Aim of experimentation:The efficacy of a new herbicide. The control we use for this purpose is called "positive control" and is represented by plots having been sprayed by a well known registered herbicide in the recommended dose. Normally this type of control is needed if we want to test the herbicidal action of a new molecule.In this case both treatments (new herbicide and known registered herbicide) have to be compared to untreated control plots which also have to be present in the experiment.
2. Aim of experimentation: Yield reduction through the use or non use of a herbicide. This is called weed index and is given by
Yield from herbicide treated or untreated plots / yield from weed free (hand weeded) plots.
In this case you need a weed free (hand weeded) control.
All treatments (inclusive controls) should be arranged according official GAP methods (EPPO methods are a good example) and should be treated with precision sprayers. Therefore farmers sprays cannot be used as treatments.
I think control treatments viz weedy check( where let the weed grow without any control measure) and weed free( devoid of weed species or providing weed free conditions at all the growth stages of the crop) are must in weed control experiments....
also in case of weed management trials, specially in case of weed dry matter and weed density, we are going to use transformation generally square root transformation or some times log transformation so as to satisfy all the ANOVA assumption as in case of weedy check, all the data related to weed density will be maximum while in weed free, it will become zero (0) that's why there will be huge variations in treatment variances, replication variances .. we have to convert these original data into small scale value so that one can draw conclusion easily..after that we have to compare performance of each treatments with these control treatments i.e. weed free and weedy check..
No doubt bestest treatment would be weed free while worst will be weedy check...it is important to compare rest if the treatment with weed free and weedy check...
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