Beginning Farmer: I was thinking about trying some dry farmed tomatoes this year and am wondering if you could share some knowledge about your world famous UCSC dry farmed tomato system?
Farmer Mentor: I think the most important take home message on the dry farmed tomatoes is that the variety Early Girl is the one that performs the best. There is a new variety available through Johnny’s called New Girl that seems to work almost as well as Early Girl.
Work your ground as early as possible in the spring to trap the residual rain moisture. Dry farmed tomatoes seem to like 20+ inches of rainfall and you definitely need some good deep subsurface clay to hold that moisture. You also need some marine influence to help moderate the daytime summer temperatures. I used to plant on the flat but switched to beds and was much happier with the results. At the UCSC farm I would spade incorporate the cover crop then form beds and work the beds with a lilliston - with sweeps in the bed middles - a couple of times to get a good "dirt mulch" over the top of the bed. This dirt mulch does a good job on minimizing evaporative loss of the deeper moisture.
As soon as the soil warms up a bit (mid may to June 1st) plant out transplants and get them as tall as possible in the greenhouse first. When planting them out bury them as deep as possible. If you have done a good job of holding the rain moisture you should be able to get the roots into residual moisture and they will readily set roots into the deeper moisture. I think the aggressive and deep rooting of the Early Girl and New Girl is what makes them so sell suited to dry farming.
We would form beds 36 inches on center and plant out every other bed. I would run a narrow Alabama shovel down the bed middle to basically open up a "V" shaped trench right down the middle of the bed. I would recommend planting the plants "in row" at between 4 and 6 feet. You can work the furrows with shallow chisels, side knives and sweeps while the plants are small and then once the plants start to grow you can come back in with the lilliston and throw some dirt at them and smother the "in row" weeds. I would recommend two or three plantings spaced out about 3 weeks apart. Some dry farm tomato growers in our region put out stakes and tie up the tomatoes. The tomatoes seem to do fine if left to sprawl out on the ground. I think it is a toss up as to whether you can recoup to cost of staking with higher quality fruit and easier harvest.
If you’re interested in learning more about dry farming, watch EFA’s Water Stewardship Project video on Dry Farming and listen to the EcoFarm Conference workshop audio recording: Dry Farming for High Quality Crops. Also check out the article and video about the Dry Farming workshop at EcoFarm 2014, "EcoFarm Conference: Dry farming a timely, popular presentation."