Media Test Review
his media test is from a poinsettia crop grown for 4 weeks. The grower noticed some yellowing of lower leaves. The pH of this test is on the ‘low side’. The grower should water with non-acidified water several times to increase the pH. When the grower begins to acidify again, he/she should consider changing from phosphoric acid to another mineral acid. The phosphorus level is high enough to supply the plant for the remainder of the growing season. A change to nitric or sulfuric acid will supply those nutrients to the plant in small amounts, and will work well for acidifying the water.
Source: • Minnesota Commercial Flower Growers Bulletin Vol. 43 No. 5