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DEPARTMENT OF SOILS MIMEO-REPORT NO. 58-4


October 1, 1958


SOIL REACTION (pH) PREFERENCES OF
CERTAIN PLANTS GROWN IN FLORIDA
by


Herman L. Breland


Department of Soils
Florida Agricultural Experiment Stations
Gainesville, Florida


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SOIL REACTION (pH) PREFERENCES OF CERTAIN PLANTS GROWN IN FLORIDA

Herman L. Breland
Asst. Soils Chemist
Soils Dept. Ag. Exp. Sta.


Soil reaction plays a very important part in the economic production

of crops in Florida. Although this fact is widely known, and is backed

up by numerous research findings, its importance has not been fully real-'

ized, Atthe present time on3y about one-half million tons of liming ma-

terials are being used in the state annually. Information obtained by

The Soil Testing Laboratory shows that about 40 percent of the soil sam-

ples tested have a pH of 5.5 or below. This pH is generally considered

to be low for many crops. There may be some misunderstanding about the

optimum soil reactions for certain plants as the available information

is widely scattered in various publications. Therefore, the grower may

not have ready access to this information. For this reason a list has

been compiled for a ready reference (Table 1.).

The soil reaction represents the hydrogen-ion concentration or

active acidity of the soil. It does not represent the exchangeable hydro-

gen which is a measure of the titratable or total acidity. Therefore,

the soil reaction does not necessarily indicate the calcium content but

it is generally a good indication of whether or not the soil needs liming.

It is common practice to speak of soils as being "acid" or "alkaline",

"sour" or "sweet" and of having a "low pH" or "high pH1". All of these

terms are rather indefinite since they do not specify as to the degree

of acidity or alkalinity. Therefore, the soil reaction (pH) may be de-

fined as the degree of acidity or alkalinity of the soil. The pH scale







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extends from 0 to 1, with 7 being the neutral point. As the pH decreases

from 7.0 the acidity increases and as it increases above 7.0 the alkalin-

ity increases. The pH scale is logrimathic, therefore, each change of

one unit on the pH scale represents a ten-fold change in the active acid-

ity or alkalinity,

In general, the pH range of soils extends from about 3.5 to 8.5, but

pH values beyond these extremes are sometimes found. Most cultivated

soils will fall within the pH range of I.5 to 7,5. Some plants grow best

in a rather narrow pH range, while others will tolerate a rather wide
range. However, pH is not the only factor that should be considered in

the production of crops. Such things as favorable temperature and light,

water control, insect and disease control, good soil, adequate plant nu-

trients, etc.,are all factors that must be taken into account if good

plant growth is to be obtained.
The pH of the soil may be raised by applying a liming material (high

calcic or dolomitic limestone, hydrated lime, marl, slags, shells, etc.)

in the correct amount. If the soil pH is too high it may also be lowered

by applying sulfur or aluminum sulfate in an amount sufficient to lower

the pH the desired amount. .







Table 1 .


Soil Reaction (pH) Preference of certain
Plants Grown in Florida

Annual Flowers Optimum pH Range*

Butterfly Flower 6.0 7.5
Calendula 5.5 7.5
Candytuft 6.0 7.0
Carnation 6.0 7.5
Cosmos, Common 5.0 7,5
Hollyhock 6.0 7.5
Larkspur 5.5 7.5
Marigold 5.5 7.0
Morning Glory 6.0 7.5
Nasturtium 5.5 7.5
Pansy 5.0 6.5
Petunia 5.5 7.0
Phlox 5.0 6.0
Poppy 6.0 7.5
Snapdragon 5.5 7.0
Sweetpea 5.5 6.5
Zinnia 5.5 7.5
Perennials Flowers
Amaryllis 5.5 6.5
Aster 5.0 7.0
Begonia 5.5 7.0
Caladium 6.0 -.7.5
Canna 6.0 75
Chrysanthemum 5.5 6.5
Crinum 5.5 6.5
Daffodil (Narcissus or Jonquil) 6.0 6.5
Dahlia 6.0 7.0
Daylily 6.0 7,5
Helianthus annuns 5,0 7.0
Lilies 5.5 6.5
Lycoris 5.5 6.5
Moraea 5.5 6.5
Physostegia (False Dragon-Head) 5.5 6.5
Shrimp Plant 5.5 6.5
Shrubs and Vines

Abelia 6.0 7.5
Arborvitae 6.0 7.5
Azalea 4.5 6.0
Bamboo 5.0 7.0
Banana 5.0 7.0
This does not mean that plants will not grow at pH values beyond
these, but the range given is considered to be the most favorable
provided that other soil conditions are also favorable.








Optimum pH Range


Shrubs and Vines (Continued)

Bougainvillea
Boxthorn
Boxwood, Japanese
Camellia
Century plant
Cherry Laurel
Coontie
Crape Myrtle
Croton
Elaeagnus (Silverthorn)
Feijoa
Flame vine
Gardenia
Hibiscus
Honeysuckle
Ivy, English
Jasmine
Ligustrum (Wax Privet)
Oleander
Pittosporum
Podocarpus
Poinsettia
Sea Crape
Viburnum
"'ax Myrtle
Weeping Lantana
Wisteria
Yaupon


Trees

Camphor Tree
Dogwood
Holly, American
Holly, Chinese
Holly, Japanese
Kumquat
Loquat
Magnolia
Mimosa
Palm, Cabbage
Palm, Pindo
Palm, Queen
Palm, Royal
Redbud Tree
Sausage Tree
Sycamore


5*0o
5.0
6.0
5.0
5.0
5.0
5.0
5.0
5*0
5.0
5.0
5.5
5.0
6.0
4.5
5.5
5.5
5.0
6.0
5.0
5.0
6.0
5.0
5.5
5.0
5.0
5.5
5.0


6.0
5.0
5.0
5.5
4.5
5.5
5.5
5.0
5.0
5.5
5.0
5.0
5.5
5.5
5.5
6.0


6.5
6.5
7.5
6.0
6.5
7.0
6.5
7.5
7.5
7.5
7.5
7.0
6.0
7.5
7.0
7.5
7.0
7.5
7.5
7.5
6.5
7.5
6.5
7.0
6.5
7.5
6.5
6.5


7.5
7.0
6.0
6.5
6.0
6.5
6.5
6.0
7.5
7.5
7.5
6.0

6.5
6.5
7.5








Grasses


Optimum pH Range


Carpet
Bermuda
Brome
Centipede
Fescue, fine-leaved
Fescue, Meadow
Italian Rye
Johnson
Orchard
St. Augustine
Zoysia
Cereals

Oats
Rice
Rye
Legumes

Alfalfa
Beans, Vlevet
Clover, Alsike
Clover, Crime on
Clover, Ladino
Clover, Sweet White
Clover, White
Cowpeas
Crotalaria
Kudz a
Lespedeza, Jap.
Lespedeza, Kor.
Lupine, blue
Lupine, white
Lupine, yellow
Soybeans
Vetch

Field and Vegetable Crops


Asparagus
Beans, lima
Beans, snap and waz
Cabbage
Carrots
Cotton, upland
Corn
Cucumber
Lettuce
Mustard
Peppers
Potatoes, white
(For scab


5.5 6.5
5.5 6.5
5.5 7.0
5.5 6.5
5.5 6.5
5.0 6.0
5.5 7,0
5.5 6.5
5.5 6.5
5.5 6.5
5.5 6.5
5.0 6.5
control pH to 5.6)


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5.0
6.0
6.0
5.0
6.0
5.5
5.5
5.0
6.0
6.0
6.0


6.0
7.0
7.5
6.0
7.5
7.0
6.5
6.0
7.0
7.0
7.5


7,5
6.5
7.0


7.5
7.0
7.5
7.0
7.0
7.5
7.6

6.5
6.5
6.5
6.5
7.0
6.5
7.0
7.0


5.0
5.0
5.0


6.0
5.5
5.5
5.5
5.5
6.0
5.5
5.5
5.5
5.5
5.0
5.0
5.0
5.5
5.0
6.0
5.5






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Field and Vegetable Crops (Continued) Optimum pH Range

Potatoes, sweet 5.5 6.0
Radishes 5.5 6.5
Rutabaga 5.5 7.0
Strawberries 5.5 7,0
Sugar Cane 5.0 74
Squash 5.5 6.5
Tobacco, shade 5.3 6.3
Tobacco, flue-cured 5.3 6.3
Tomatoes 53 -.7.0
Watermelons 5.0 6.0
Turnips 5.5 6.8