Adjusting the PH and NPK of my garden beds

Asked April 29, 2020, 7:52 PM EDT

Hi ! did a soil test of my beds after not doing one for many years. The PH was 7.5, Nitrigen was very low, Phosphorus was very high, and Potassium was very low. I usually amend with composted bagged chicken manure, Compost from our residence, oyster shell and greensand or kelp meal yearly. How do I correct this soil for a wide mix of vegeaables. My peas are growing but look lanky compared to last year. I have cabbage, lettuce, kale and chard in too but they look fine. Help! Wendy

Washington County Oregon

1 Response

This is one of the issues we have been finding as our long-term mantra has been to add organic matter to improve the native clay soil. Peas are legumes and typically do not need additional Nitrogen since they can fix N through a bacteria that grows on the roots. You can purchase the inoculum but that is best done at the time you plant. If you plan to plant beans (pole or bush) you can use the same product. To lower pH, Sulfur is the typical addition but you can burn the roots if you apply elemental sulfur on seedlings. You can meet the N and S by using an ammonium sulfate fertilizer. However, there are specific calculations for how much you would need to actually lower the pH.

I found this article from Iowa State that can give you some ideas https://hortnews.extension.iastate.edu/1994/4-6-1994/ph.html