Sugar Additives and Growth After Germination

If molasses benefits plants due to its sugar content, then maybe other sugars or carbohydrates added to the soil would also increase growth. I encouraged some of my students to test this hypothesis by suggesting they test the effect of adding sugars to sunflower seeds in potting soil. (Sadly, I did not have molasses the day we set up the experiments) We watered plants right after the seeds were planted. Each group watered half their plants with the additive (sugars or Fox Farm Big Bloom were tested this semester) and the other half of the plants only got tap water. We then reapplied the additive each week for three weeks until we measured plant growth. (Additives were 5ml per 1/2 L of: Coke, 5 hour energy drink, tea that had dextrose sugar and straight table sugar (sucrose). All plants were watered with tap water as needed throughout the rest of the experiment. We saw no increased growth (measured via height and biomass) in any sugar groups after three weeks. The Fox Farm group was significantly bigger in height and biomass. An interesting observation was most of the sugar additive groups had mold (no other pots had mold accept one’s that had added sugar). This mold may be related to the most important piece of data, that there was a significant reduction in percent seed germination found in groups that used sugar additives compared with those that added high phosphorus fertilizers or just tap water.  I would not recommend using sugars until your plants are larger and more established and interacting with soil organisms that are beneficial. I hypothesize that by adding sugar before the seeds germinate you are making it easier for harmful microbes that are wide spread in the environment and better adapted to take advantage of a sugary environment to dominate the soil. By adding sugar once the plant is larger and has established a relationship with beneficial microbes (already in place) the beneficials will thrive with the new food source and so will your plant. Next semester I will be sure to bring in molasses… until then, stay tuned and…

Good Growing,
Dr. E.R. Myers