Question
My name is Jessica Goines.  I am in the 8th grade and I am doing a science fair project on growing plants.  The question I am dealing with is will a plant grow better with water or with milk.  My hypothesis was that I thought that milk would help a plant grow more.  I thought because of the nutrients that it would add to the soil.  I seemed to be wrong and my seeds did not sprout and my plant is turning yellow and only mold is growing.  I am having a difficult time trying to find out why the plant will not grow with milk.  I know why water works because of the photosynthesis and CO2.  I was just wondering if you could give me any information that could help me or where I could research this.  Thank you for any response you may have.

Answer
Here is the answer from the MadSciNet----http://www.madsci.org/

The proteins, fats, and sugars in milk and sugar in sugar water provide a food source for microbes, especially bacteria. The bacterial waste products probably
cause the bad odor. Bacterial waste products may also harm the plant roots. The rapidly growing bacteria will also compete with plant roots for mineral nutrients supplied by the soil and possibly soil oxygen. They might also alter
the soil pH in a way adverse to plants. Sugar water, depending on the sugar concentration, can also lower the availablity of water for the plants via an osmotic effect. Milk may do the same thing to some extent.
Unlike animals, plants do not directly use the proteins, fats or sugars in milk or sugar in sugar water. Plants only absorb mineral nutrients and water from the soil.