Twentieth century zinc research has discovered that a lack of zinc is expressed in plants as rosettes,
low vigor, poor leaf development, and eventual death progressing from the terminal branches. Zinc
is unavailable in alkaline soils because of formation of insoluble ZnCO3 and in acid soil where zinc
is in competition with nickel. Foliar application has proven difficult because of cuticular barriers as
leaves become mature. Frequent zinc foliar applications are more successful than occasional treatments.
Traditional ZnSO4 foliar treatments have proven inadequate compared to a nitrate-based zinc
spray. The new formula is NZN consisting of Zn(NO3)2+NH4NO3+urea. Nitrogen is superior to
sulfur for many reasons in enhancing zinc absorption. Nitrogen is an integral part of all amino acids,
whereas sulfur is found in only a few. Sulfur accumulates on the surface of treated crops and can
cause spray burn in many. Nitrates are hydrophilic and sulfates are hydrophobic which influence
their ability to enter cuticles of treated crops in arid environments.
The increase from 200,000 to 12 million pounds of pecan production in the 30 year span from
1967 to 1997 of the zinc research in the Trans Pecos area of Texas is more than a coincidence
(USDA Agricultural Statistics, Texas Department of Agriculture, 1997). This comparison is more
justified than in other areas because lack of zinc was the limiting factor in that area. The zinc nutrition
problem that confronted the industry in 1965 has been solved. Obviously, the efforts of a number
of hard-working pecan growers and horticulturists were instrumental in securing this massive
There has been a long, unsuccessful struggle to develop a rootstock that will facilitate zinc root
absorption. A small percentage of pecan seedlings will absorb and transport zinc. Zinc-regulated
transporter proteins have been found in some pecan seedlings that promise to revolutionize the
pecan industry and other species. This development is the future to which we can all look, for all of
our zinc-deficient species. The preceding horticulturist and agronomists cited in this sections have
discovered the problem. Now the next generation, using advanced technology like zinc-regulated
transporter proteins, will eliminate the expense of foliar sprays and soil treatments.