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News and information from UC Cooperative Extension about alfalfa and forage production.
Tractor & Hay bales
by Jim Anderson
on March 11, 2014 at 1:11 PM
When we used to flood irrigate we would often have very much the same condition. Even with sprinklers if pooling happens the alfalfa will yellow on us in some of our fields. Especially our fields that are mucky silty clay loam, have water tables of 18-36 inches, and classified as poorly drained (by NRCS Web Soil Survey)  
My vote is too much water.
by Vern L Marble
on March 17, 2014 at 10:47 PM
This yellowing is caused by bicarbonate induced iron chlorosis. I have observed this problem often, since my undergraduate studies at Utah State Univ., and in California & Nevada. It seems to occur especially in alkaline soils above a pH of 8.2-8.4, after irrigation or rain, on heavy soils, during cool periods, and in the spring, and when a high concentration of CaCo3 in the upper 12 inches is present.
Reply by Daniel H Putnam
on March 17, 2014 at 11:00 PM
Great to have you confirm the iron chlorosis, Vern. I've seen this symptom also on high pH soils during wet cool periods on heavy soils.  
It's ironic (get it) that this occurred due to EXCESS moisture in a drought year.
by Glenn Shewmaker
on March 21, 2014 at 4:36 PM
We also see this after 1st cutting in Idaho on furrow irrigated, basically flood also. We have high pH and high bicarbonate and the oxygen-biological limiting environment.  
Vern, what were the iron concentration in a tissue test?
by Bill Wilson
on March 26, 2014 at 4:46 PM
It is nice to have company. Misery loves company.  
I though it was caused by high calcium levels. After all the soil here is calcareous, with an 8 pH, 8,500 ppm Ca, Plus 4% to 6% free lime.  
Then Matt Hagny a crop consultant up in the Western Corn Belt explained the function of calcium bicarbonate.  
on occasion alfalfa or bermudagrass will have a tissue analysis of 300 or 400 ppm Fe, though the usual is in the 100 ppm range. HERE we seldom have visual signs of iron chlorosis in our field crops. Yard fruit trees are a different matter. Peach and pair trees suffer with iron chlorosis no matter hoow much iron is dumped into the ground or sprayed on the leaves.  
To add to the excitement we have high shrink clay soil.  
Work with the soil and forget Virginia garden soils will save our sanity.
by Hugh
on June 13, 2015 at 2:44 PM
Iron. The green veins give it away. Saturated soil and Ph above 7.5 creates iron problems. Spray with chelated iron. Broadcast 300# of elemental sulfur per acre.
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