It's always exciting when you have tomato plants growing in your garden during the summer months. A study conducted by Benha University in Egypt found that a yeast extract solution at around 4 fluid ounces per gallon, sprayed onto tomato plants, did increase yields. The solution was made from dry yeast with added sugar for activation, and then diluted with water. Similar research was conducted by the University of Queensland using brewer's yeast to enhance the growth of tomatoes and sugarcane. This study found that the yeast helped to increase root growth and the uptake of nitrogen and phosphorus.