Fertilizing blueberries and managing soil pH in sandy soils
Dear Extension Office, I am growing blueberries on sandy soils, mulched with sawdust and irrigated with water acidified with nitric acid down to ph 5,5-6. Initial pH of the water is near 8. Soil analysis performed 4 years ago indicated pH at 2.9 (measured in KCL). Magnesium lime was applicated two subsequent years at low doses. Now the pH is 3.9 (KCL) and I am wondering what type of nitrogen source would be best is this scenario. For the last 3 years I have been using urea solely. I am considering still using urea to change soil pH in minimal degree. Or is it better to swap on ammonium sulphate ? I would appreciate for Your suggestions and opinion.
Urea is less acidifying than ammonium sulfate, so I would continue to use urea. You might consider supplying a portion of the annual N as poultry manure if that is available to you. It is often a good N source and can also tend to raise pH somewhat. Use only low rates and spread it down the row rather than placing it right next to the bushes. Only use 100-200 lb per acre.