P deficiency reduces fertility and fruit setting considerously, resulting in poor yield.
P deficiency results in reduced growth and dark green leaves, often with some bronzing to purple lesions on the leaf blades. Discoloration starts at the margins and spreads over the interveinal areas. The leaves become hard and stiff. Dormant buds contain only small flower primordia what reduces the performance of the vines.
Phosphorus deficiency Phosphorus deficiency occurs rather seldom in the fields.