My blueberries are yellow
Asked June 22, 2019, 4:10 PM EDT
A couple of plants in the plantations have a yellow color of leaves with green veins. Whether it is iron chloride. The root is Duke and in most cases the symptoms appear on older plants.
I checked the pH value of these plants and obtained the following values:
sample 1 pH 4.30
sample 2 pH 5.50
sample 3 pH 5.80
sample 4 pH 5.90
average value of pH 5.37
Plants are planted on the soil with slightly higher clay content.
What led to chlorine and iron blockade when the pH value is at the upper limit of optimum. What measures can I take to give the leaves a normal color?
I'm sending a couple of photos attached.
Thank you for helping
Yes that is iron chlorosis caused by the soil pH being too high and reduced iron availability. Duke is pretty finicky about soils and seem to show this symptom when the soil pH is above 5 so your samples are all high. In addition the higher clay content makes it hard to change the soil pH.
You can green up the plants with a foliar iron spray which will green them up in a couple days but the effects will fade. Commercial growers routinely add about 100 to 500 pounds of sulfur an acre to keep the soil pH down. Do you irrigate? If the irrigation water has any lime in it you will be raising the soil pH with each irrigation. We recommend only using Ammonium Sulfate (AMS) 21-0-0 for the nitrogen source if the soil pH is 5 or above. I have never had much luck with just applying AMS around individual plants but sometime using an ammonium phosphate fertilizer green them up a little. Hear is a link to an article I wrote on soil pH in blueberries. https://www.canr.msu.edu/news/soil_test_before_you_plant_blueberries.
It links to this fact sheet I wrote on changing the soil pH with sulfur. The link is bad it got lost when they updated the blueberry website. Here is a good one. https://www.canr.msu.edu/uploads/files/Lowering_Soil_pH_with_Sulfur.pdf
I discuss how much sulfur to use and in the table I state that you can substitute iron sulfate but you need to use 8 times as much. The advantage of the iron sulfate is that it works pretty quickly and you may see the results in a couple weeks instead of a couple years. You can back calculate for individual plants by dividing the rate per acre by the number of blueberries per acre in you planting to get a rate per plant. I would only use half the rate you calculate per plant to stay on the safe side. The material should be applied evenly across a 3 foot circle centered on the plant to avoid burning the roots. I would suggest you do the foliar spray and then try to fix the problem with the soil and you should see positive results form the soil treatment next year.
Let me know if you need anything else