Molybdenum (Mo) & Nickel (Ni)
Both these nutrients are needed in very small amounts in fruit trees. Deficiencies have never been documented in the field, so leaf threshold levels have not been established. When we have analyzed leaves for Mo, values have generally been between 0.04 and 0.30 ppm. Molybdenum deficiency has been induced on myrobalan plum in sand culture. Symptoms include small leaves and irregular areas of necrotic tissue on tips and margins of leaves.
Nickel has been identified quite recently as an essential nutrient in plants. Thus, very little is known about its role or required amount in fruit trees.