The Effects of Molybdenum Fertilizers on Blueberries

Blueberry Nutrients

• Oxygen, hydrogen and carbon are found in the air, but the rest of a plant's required nutrients need to come from the soil. The macronutrients are nitrogen, phosphorus and potassium, which are needed in higher amounts for proper growth. The micronutrients are only required in small amounts, but they can cause problems with the blueberry bush's health if they are absent or in excess. Molybdenum is one of the micronutrients that is needed in the lowest concentration as compared to the other micronutrients.

Molybdenum

• Molybdenum is used as part of the enzyme system that is part of nitrogen fixing. So, the first symptoms of molybdenum deficiency are nitrogen deficiency symptoms. Protein synthesis and sulfur metabolism can be affected. This is important to an acid-loving plant because sulfur is used to make soils more acidic. The element also has an effect on pollen formation, which affects fruit production, another important consideration on blueberry plants. Blueberries need 3 oz. per 2 lbs. of soil of molybdenum.

Molybdenum in Acidic Soils

• Molybdenum availability increases as soil pH increases, and sandy soils tend to be low in molybdenum. This affects blueberries because they often grow in sandy soils and prefer a soil with a low pH. Both conditions mean the plant could show signs of molybdenum deficiency.

Fertilizer

• Fertilizers contain trace elements. Because plants generally need such small amounts of molybdenum and it is usually sufficiently found in soils, there are no fertilizers with high concentrations of the element. It is found in blended chemical compounds that help deliver it in the right concentrations. Ammonium molybdate has 54 percent molybdenum, molybdenum trioxide has 66 percent and sodium molybdate has only 39 percent. There are no tests for soil levels of molybdenum but visual symptoms such as curled leaves, yellowing at the margins and low fruit production may be clues. The rate is only 2 to 3 oz. per acre of water as a foliar spray if deficiencies are identified.