General Information:
NIPAN LLC has developed a foliar nickel fertilizer called Nickel
Plus to correct mouse ear in pecans and provide yield and quality benefits. Nickel Plus contains 5.4% nickel as nickel lignosulfonate
and 5% nitrogen to assure efficient absorption by the foliage. Depending on when the application is made, a growth response
generally occurs within 3 to 4 weeks after application. Nickel Plus has been tested by the USDA and the University of
Georgia.
Background:
A deficiency of nickel was discovered in 2003 to be the cause of "mouse ear"
of pecans. The USDA at the Southeastern Fruit and Nut Laboratory in Byron, Georgia made this discovery after many years of
research. Originally termed "little leaf", it was later called mouse ear and is typically identified by leaflet
deformity shaped to resemble the ear of a mouse.
Mouse ear can affect an entire tree or occur randomly throughout the
canopy as single major limbs or in terminal branches. It generally appears on the spring flush and can consistently reappear
from year to year or occasionally on the same tree.
Coastal plain soils in the southeastern US contain very little
nickel and pecans have higher requirements than most crops. Root uptake in pecans is inefficient and inhibited
by the high levels of zinc found where pecans are grown. In the southwest, alkaline soils cause nickel to be unavailable to
the roots. Mouse ear is actually the symptoms of a urea toxicity caused by the buildup of urea in leaf tissue when there is
a severe deficiency of nickel. Nickel is required by the urease enzyme in plants for the efficient conversion of urea
to ammonia. When the foliar concentration of nickel is less than 5 ppm Ni, the trees is less efficient mobilizing stored
nitrogen in the spring.
Symptoms of nickel deficiency in pecans include:
● pale green and curled foliage
● necrosis of leaf or leaflet tips
with dark
green zone adjacent
to necrotic zone
●
brittle wood (reduced lignification)
● reduced growth, vigor and flowering
●
dwarfing, short internodes
● weak shoot growth, failure to survive dormant season
(cold injury)
● pointed buds
●
rosetting, loss of apical dominance
● dead or dark colored roots, reduced number of feeder
roots
● death of shoots and limbs
Nickel is not included in standard fertilizers because most crops do not
need additional amounts and root uptake is poor in pecans. Nickel Plus was developed specifically for pecans to be applied
at 1-2 pints/acre starting when the trees are in the parachute stage. This application time is particularly important
to assure efficient utilization of stored and applied nitrogen. A second application 30 days later will prevent the reoccurrence
of mouse ear and can reduce early season nut drop by as much as 10%. A third application in mid-July in combination
with a fungicide has been shown to reduce the incidence and severity of scab on the nuts and reduce water split. Maintaining
the foliar concentration of nickel between 5 and 15 ppm is considered necessary to achieve these benefits.
Most pecans trees experience a "hidden hunger" for nickel not showing any of the symptoms associated
with a severe deficiency.
If mouse ear symptoms are present in the late summer, an application of 2 pints/acre
in late September to early October will prevent mouse ear in the spring flush and assure efficient utilization of nitrogen
when the shoots are rapidly expanding.
Nickel has been extensively studied in other crops and has several significant
roles in plant growth and development. Recent research in Georgia has identified key benefits in pecans that include:
● Improved nitrogen efficiency
● Reduced early season nut drop
●
Reduction in water split
● Stimulates natural defenses against plant diseases
●
Reduced incidence and severity of scab
● Improved lignification for stronger wood
