With all the quantative data available today it would seem likely that there would be an exact answer to this question. In actuality, it is very difficult to ascertain the answer. Some grain crops must transpire many thousands of gallons of water during their growth cycle to produce a single bushel of grain. While others require much less water and may produce a different yield used for a different purpose. Thousands of gallons of water may be used in the food processing industry to create a certain food item from a single grain. It's highly speculative using the size or texture of a food to determine how much water may have been used to grow it.
Land and Water scientists have used precision weighing systems to measure water use by various crops, and the yield from the crops. The following approximate figures were revealed:
To produce one kilogram of oven dry wheat grain, it takes 715 - 750 liters of water:
- For 1 kg maize, 540 - 630 liters
- For 1 kg soybeans, 1650 - 2200 liters
- For 1 kg paddy rice, 1550 liters
- For 1 kg beef, 50,000 - 100,000 liters
- For 1 kg clean wool, 170,000 liters
These figures were determined in very controlled conditions. They can vary with the environment and with the methods of water delivery and harvesting used. Although many people react with amazement at these figures, we should be cautious about interpreting them. The numbers don't necessarily imply that some types of food are better than others. They do emphasis the large amount of water that is needed to grow food, and demonstrate that we should be investigating ways to conserve and improve water use efficiency.