AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Summer 2003, No. 3
A common cry from the urban areas is that agriculture uses more than its fair share of water. Some estimates have been made that more than 80 percent of developed water is going to agriculture in many areas. Attention has been drawn to the fact that agriculture loses too much water through cracks, seepage, and evaporation from the miles of canals and pipelines. These losses should be addressed when financing is available.
What is not well understood is the huge amount of water that is indirectly delivered to cities in the form of food. A report by the Water Education Foundation documented the amount of water required to produce various foods in the Western U.S. Their basic approach was to divide average evapotranspiration by average yields to determine the gallons of water per pound of food produced. Since some of the water delivered to a farm is unavoidably lost as deep percolation, runoff, or soil moisture storage, the irrigation efficiency was assumed to be 70 percent.
Using a typical 2,300-calorie menu proposed by the U.S. Department of Agriculture, the following meal was constructed. The gallons of water required to produce that particular food item are shown.
Proper plant nutrition is a vital key to achieving efficient use of water. Nitrogen deficiencies have an impact on the ability of a crop to convert available water into yield. Phosphorus is important in stimulating seedling root development. This helps the plant explore more soil, increasing the recovery of nutrients and water. Potassium is often referred to as the regulator nutrient, influencing the water dynamics in plants. Nutrients play an essential role in allowing plants to convert water and sunshine into food.
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