This year I'm planting my tomatoes in a single row with baling twine on either side. More baling twine will be added as they grow and in theory I will keep up with the pruning. I have tooed and froed on the decision for quite a while. We are hoping for ease of picking, good air circulation and a better environment for late ripening. We were impressed with Burwood prize last year so have grown it again but plan to control it a bit more. College Challenger is making an appearance as something new and the Purple Cherokee , which is one I have been saving seed from and improving over the years. It's a beautiful tasting tomato which I have been selecting to get less splitting of fruit. I'm doing this by selecting fruit from plants with more rounded fruit and less imperfections which can pave the way for splitting. Also doing KY1 on weed gunnel plastic sheeting so the fruit at ground level won't get as damaged due to soil contact. The Ky1 is determinate so will finish early enough for me to plant another winter crop. Then the black cherry and as yet, some other cherry varieties which I have yet to obtain. So they are in the ground and although the weather is not overly warm I'm pretty sure there won't be a frost bad enough to do damage. Looking forward to making more of our smoky pizza oven passata and tasting the first tomato of our season which at the best will be in Jan - probably late Jan.
Found this paper which supports my 30cm spacing, although the climate is probably a little drier where this study took place. They also recommend 3 stem pruning for higher yield.
From the findings of this study it could be concluded that pruning of tomato could be practiced to increase the yield and quality of tomato. An intra-row spacing of 20-40 cm was appropriate for maximum fresh tomato yield and quality. Three-stem pruning coupled with closer intra-row spacing (20-40 cm) may be recommended for higher production of tomato variety (Roma VFN) in the Sudan savanna of Nigeria.