Oklahoma State University
Stillwater, OK

Oklahoma Alfalfa
Oklahoma Cooperative Extension Service
Oklahoma Agricultural Experiment Station

 

How Much Water Does Alfalfa Need? 

  
  
Anyone who has grown alfalfa even a few years knows it needs a lot of water to produce high tonnage. In fact, on the average, alfalfa needs about 6" of water in the soil available to the roots for each ton of dry matter produced.   

If your soil can store 2 inches of water per foot of depth and roots go down to 10 feet, you should be able to produce about 3.3 tons. If the roots are only 2 feet deep (the case of some of the seedlings), production will be limited to recent rain because so little is stored within reach of the roots.   

Where does this water come from?   

  • It might be rainfall or snow.  
  • Water may come from shallow aquifers 10 to 25 feet deep.  
  • It may also come form "run-on".  That is the water that runs off surrounding areas onto the alfalfa field.  
  • We also have about 15 to 25% of our alfalfa that is irrigated with well or surface water.  
No matter where the water comes from, it must be in the root zone.  Knowing the amount of water required for alfalfa lets producers predict their yields.   
  
John Caddel, Forage Agronomist 
Department of Plant and Soil Sciences 
Oklahoma State University 
 

 
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