Correcting pH-Induced Manganese Deficiency in Bermudagrass Turf‘
Manganese deficiency of ‘Tifgreen’ bermudagrass
rnugenissii Hurcombe) turf has been observed
South Florida when soil pH exceeded
as a result of irri-
gation with alkaline water. A 2-year field study on Pom-
pano fie sand (a siliceous, hyperthermic, typic Psam-
maquent) was designed to evaluate three approaches to
correcting this deficiency:
acid forming N sources, 2) Mn fertilization at rates up to
g/m* using MnSO,, a Mn-chelate, or a Mn-frit, and 3)
MnSO, fertilization in combination with a series of fungi-
cidal drenches for suppressing Mn-oxidizing soil fungi.
Sulfate and chelate Mn sources provided short-term cor-
rection of the deficiency, but little response to the frit
source was noted. Sustained correction was achieved with
MnSO, in combination with the fungicidal drenches.
However, adequate Mn nutrition was obtained even in the
absence of Mn fertilization when soil pH was maintained
with acid-forming N sources. This treatment ap
pears most suitable for turfgrass, since considerable N
commonly is used in turfgrass production.
ANGANESE deficiencies are well-documented in
many plants, but few cases of Mn deficiency or
to Mn have been reported for turfgrasses.
In fact, turfgrasses are relatively insensitive to most
micronutrient deficiencies other than Fe and Cu (4).
Nevertheless, Mn deficiency was observed in Florida
as early as 1948 (2), but the documenting evidence
was not widely circulated or noted. We have observed
Mn deficiency of ‘Tifgreen’ bermudagrass
Hurcombe) on several occasions at the
Agricultural Research Center in Ft. Lauderdale. For
example, plots receiving N from CaN [Ca(N03)2]
were chlorotic and grew poorly compared to those fer-
tilized with AS [(NH4)2S04] (13). Growth and color
were improved when MnS04 was applied to the CaN
plots, although growth remained inferior to AS plots
receiving no Mn. Growth and color were nearly as
good in CaN plots that received weekly fungicide
drenches as in AS plots.
Manganese availability is inversely related to soil
pH. The oxidation of divalent Mn to less soluble
forms occurs in the pH range
7 to 8 primarily as a
result of microbial activity (10). Numerous fungal
species have been implicated in this transformation
Although the sand-textured Entisols and Spodosols
of south Florida generally have very acid surface hori-
zons, the pH of these poorly buffered soils can increase
rapidly when irrigation water high in pH and calcium
bicarbonate is used. In south Florida, limestone bed-
rock may be found at
to 2 m or less in depth. Drain-
‘Contribution from the Agric. Res. Ctr., Univ. of Florida In-
stitute of Food and Agricultural Sciences. Florida Agric. Exp.