Agriculture Reference
In-Depth Information
Table 3.4
Nutrient Mobility and Visual Symptoms of Deficiencies in Grapevines
Nutrient element
Mobilityandappearanceofsymptoms
N
Mobile;overallreductioningrowthanduniformleafyellowing
P
Mobile;bronzecolorationinolderleavesearlyintheseason
K
Mobile;startsasayellowingofolderleafmargins;asdeiciencyworsens,
margins die and curl upwards
S
Mobile;deiciencyrareinvineyardswhereSspraysareusedtocontrol
powdery mildew; symptoms similar to N deficiency
Ca
Veryimmobile;shoottipsstuntedandmaydie
Cl
Mobile;nodeiciencyseenbecauseClisubiquitousandreadilyabsorbed
Fe
Immobile; young leaves show interveinal chlorosis; when severe, leaves
may become very pale before developing necrotic (dead) spots
Mg,Mn
Mobile;interveinalchlorosisstartsonolderleavesand,whensevere,
necrosis extends inward from the leaf margins
Zn
Relatively immobile; stunted lateral shoots with small leaves showing
“blotchy” interveinal chlorosis; fruit set may be affected; bunches show
a “hen and chickens” appearance
Cu
Immobile; shortened internodes and death of shoot tips similar to Ca;
flowering also affected; rare in vineyards because of Cu sprays
B
Immobile; occurs in older leaves and may be confused with Zn deficiency
because of “hen and chickens” appearance; the range between
deficiency and toxicity is small
Mo
Immobile; necrosis of leaf margins; affects pollen tube growth and
fertilization, resulting in poor fruit set
of a “hidden hunger” for the element, as illustrated by the relationship between
fruit yield and a nutrient's concentration in vine leaves (figure 3.8). This rela-
tionship is the basis for diagnosing a vine's nutrient status by plant analysis
or tissue testing. Figure 3.8 shows that as yield increases up to a maximum
with increasing nutrient supply, the nutrient concentration in the tissue also
increases. The degree of deficiency is indicated by where the plant's analysis
lies on the approximately linear trendline between severe deficiency and the
optimum range.
Figure 3.8 also shows the critical value of nutrient concentration below
which an increase in supply leads to increased yield. Note that in the “luxury
consumption” range, yield may decline as a result of nutrient imbalances or
outright toxicity. For example, too much N encourages vigorous growth that
can cause excessive shading of basal buds, which leads to lower fruitfulness
the following season. Excess N can predispose to “false potassium deficiency”
under cool and variable weather in spring due to a K/N imbalance and may
also cause early bunch stem necrosis.
