In my years as a gardener there have been many shared attempts to increase tomato fruit yields. The best way to do this(after the plants are in the ground) is to do the best you can with what the plants are giving you.
Over dosing the garden with heavy fertilizer is not only harmful to the plants, but creates an unnecessary excess of chemicals in the surrounding earth and eventually YOUR drinking water. Here are some common problems and solutions that fit with my gardening techniques.
Problem: fruit cracks open before fully ripe leaving a portal for disease and insect invasion
Answer: Unequal watering during the growing season seems to plump up the innards of the fruit and the skin does not have the time or elasticity to grow along with the pulp. Some years are better/worse for this condition and you can save yourself some split-fruit by monitoring the natural rainfall and compensate with supplemental watering.
Ideally, one inch of rain per week will grow you healthy fruit. We all know that this natural watering regiment is rarely granted to us, so attempting to artificially create a situation where the plants get near one inch per week is required.
Caution, do not attempt to over saturate your crop if they did not receive their inch per week for a few weeks. Say, you go on vacation and the plants are wilty. Your first instinct may be to soak them BUT this is just the recipe for fruit cracking. The plant has accustomed itself to a dry spell and if soaked out the innards will plump without the skin and that equals cracked fruit. Rather, feed them just the inch per week as suggested and the plants should perk up if they are not too far gone.
Problem: fruit ripens at the bottom but not the top
Answer: This problem usually happens during the hottest part of the summer. The scientific explanation that I heard on a radio program years ago suggests that the green tomatoes contain chlorophyll. This is the stuff in the cells that do photosynthesis. It makes sense to me that the plant wants as much photosynthetic material as possible, and does not allow the top of the fruit to ripen like the shaded bottom half so that the plant can convert more sunlight into sugar (food for the plant). A simple solution is to pick the fruit when the bottom is ripe and allow the top to ripen on the window sill.
You may notice that the tomatoes at the bottom shadier part of the plant do not exhibit this “green shoulders” problem. This is because the amount of light reaching the shady fruit is not sufficient for the plant to desire photosynthesis to occur at the fruit. With that said, another solution to this problem is to shade the fruit that have access to full sun.
Remember, ripening fruit is an annuals way to prepare for the future (winter death) and by producing a tasty flesh around the seeds, there is a greater chance that the offspring plants will be dispersed in a fertilized patty by some herbivore. The plant has no volition, but if it did there would be a desire for it to make as many of its offspring seeds grow in as many different locations as possible. Since we gardeners do not share the plants wishes, we can sometimes outsmart its motives and increase yield for ourselves. Yum.