I don't know how you got onto strip till and cost comparisons etc - I don't think I was suggesting that at all. I merely suggested about being careful about making general conclusions from any yield data.

As far as population comparisons in twin rows, I think if you are trying to make a return on investment comparison the two plots (single 30" vs twin rows 7.5" apart on 30" ctrs) they should be planted at the same population. THEN you will see any improvement due to the twin row system itself.

Spacing of the single row plants in the row and the uniformity (or mostly lack of from what I have seen in the field) of the seed stagger in twin rows could be another factor affecting the outcome of your experiment.

My point is that IF you plant twin vs single AND up the population you are introducing two variables into the experiment and it is impossible to say for sure whether any difference is due to the twins OR the higher population without more replicated trials. This is the essence of experimental work and one of the several reasons that many simple magazine "experiments" are maybe not the whole story.  Ask a corn breeder what it takes to prove a statistically significant yield difference is due to any one factor...you will get an earful.

I am not being critical, I think your trial is interesting. Please let us know how it looks through the season and into harvest. Thank you.

Jim at Dawn