Everglades Station Mimeo Report EES68-9 May 1968
Some.Soil pH Effects on Soil Tests and Growth of
Some Vegetable Crops on Everglades Organic Soil
H. W. Burdine and V. L. Guzman-
The pH of our organic soils is one of the most important soil test deter-
minations made for planning treatments and cropping procedures that must be
followed for maximum yield and quality of vegetable crops. It has been com-
pared to taking the temperature of a patient by a physician. It affects the
solubility or availability of plant food elements to plants. As the reaction
goes down from pH 7, the condition is more acid, as it goes up from 7, it is
more alkaline. The most favorable soil reaction for most vegetable crops seems
to be on moderately acid soil, about pH 5.8. Within the normal ranges found on
the organic soils, availability of calcium, phosphorus and manganese are most
affected, with the latter most frequently affecting plant growth. However, as
will be shown further in this report, not all crops or even varieties within
the same crop will respond to pH for the same reason, nor is the same pH
mentioned above most favorable for all crops under the same specific conditions.
A. Changes in soil reaction:
The following data taken from experiments conducted over a period of years
indicates that soil reaction is not constant and pH tends to drop following
fertilization and crop growth. It is assumed, but not established, to return
more or less to its original level during the summer fallow period unless
flooded. The purpose of the following table is only to show that pH may not
remain constant, but probably drops under crop growth. The second samplings
were mostly taken before fertilization, but not all. The third samplings were
mostly taken at the end of experiments, but not all.
Table 1. pH differences from the same plot areas during experiments.
Plot Before Plowing Second Sampling Third Sampling
No. Date pH Date pH Date pH
*1. Sept. 1 7.26 Sept. 18 7.25 Nov. 3 6.51
2. Jan. 12 6.58 Feb. 6 6.50 March 17 6.01
3. Nov. 10 6.63 Dec. 2 6.52 Jan. 19 6.39
4. Nov. 3 6.70 Dec. 10 6.27 March 16 6.28
5. Jan. 19 6.72 Feb. 10 6.38 May 15 6.24
6. Sept. 24 6.48 Oct. 18 6.43 Dec. 23 6.03
*7. Nov. 28 7.00 Jan. 6 6.41 March 19 6.24
*8. Dec. 10 7.00 Jan. 2 7.00 April 3 6.63
Fields previously flooded.
/ Associate Soils Chemist and Horticulturist, respectively, Everglades
Experiment Station, Belle Glade, Florida.
B. Effects of pH on some soil test results:
The following soil test results made under routine Everglades Experiment
Station soil test procedures are taken from plots where pH levels were lowered
with agricultural sulfur. Soil phosphorus was determined from distilled water
extraction and calcium and magnesium from 0.5 N acetic acid extraction. Samples
from all plots were taken at harvest following uniform fertilization of each
plot. For the sake of brevity, potassium determinations are omitted as pH
effects on potassium levels in both soil and plant tissue were not found to be
Table 2. Soil test results as influenced by adjusted pH.
Calcium and Magnesium were not
Plots 5 and 7 were located on sawgrass peat. Plot 6 on Okeelanta peaty muck.
The increasing solubility of phosphorus as pH levels were lowered shows
what happens to soil phosphorus levels when the pH levels on highly fertilized
high pH soils are lowered.
C. Some crop responses to pH adjustment:
1. Early Experiments
When celery yield and quality data were originally correlated with Ever-
glades Experiment Station soil tests, a golden type celery was being grown
and used to obtain the necessary data. It showed a large response to pH levels,
which may have been in large measure due to manganese availability as the
seedbed experiment cited definitely indicates.
Table 3. Effects of pH adjustment on growth and Mn content of a golden celery
b. Field experiment:3/
Soil pH and average
of petiole tissue
pH Mn ppm
Table 4. Effects of pH adjustment on yield of a golden type celery and soil
2. Recent Experiments
Following a change in celery types a series of experiments were conducted
with the following typical results:
Table 5. Effects of pH adjustment on seedling growth of a Sunmer Pascal and
Utah 52-70 celery.
1. P. P. V. Summer
pH Sq. Foot
2. Utah 52-70
b. Field experiments:
1. The following data with Utah 52-70 is typical of data obtained from two
such experiments. Yield data are in pounds for 30-foot single row plots.
Supplementary boron and manganese were sprayed as treatment variables to
- Forsee, W. T., Jr. 1949. The effect of soil pH upon the growth of celery
seedlings on the peat and muck soils of the Everglades. Proc. Fla. State
Hort. Soc. 62:143-146.
SForsee, W. T., Jr. 1950. The place of soil and tissue testing in eval-
uating fertility levels under Everglades conditions. Soil Sci. Soc. Amer.
determine the limiting factors of varying pH levels. Manganese and boron in
the fertilizer mix totaled 10 Ibs. MnO and 5.4 Ibs. B203 per acre.
Table 6. Effects of pH adjustment and boron and manganese spray treatments on
Utah 52-70 celery.
pH at Lbs./plot Cracked Petioles/30 plants
Harvest Check Boron spray Mn spray Check Boron spray Mn spray
6.28 150 162 149 46 17 47
5.99 146 154 149 25 22 26
5.74 152 151 152 30 15 33
5.41 155 145 156 20 11 19
Table 7. Chemical data from outer Petiole tissue, all from check plots, dry
weight basis, of Utah 52-70 celery grown on varying pH levels.
pH P % Ca % M ppm Mn ppm
6.28 .53 2.17 .27 7 42
5.99 .57 2.02 .28 16 47
5.74 .59 1.89 .26 23 44
5.41 .61 1.87 .28 36 45
Differences in phosphorus, calcium and manganese contents of petiole
tissue were highly significant, and it was concluded that the significant
yield response on the high pH level where boron was sprayed was due to a
higher boron/calcium ratio. Manganese spray effects were significant in none
of the experiments conducted. It was concluded boron sprays were of value on
higher pH levels, but may actually reduce yields on pH levels below 5.5 with
Utah 52-70. Neither pH levels, nor supplementary nutritional sprays signifi-
cantly affected Summer Pascal.
2. A further experiment was conducted with Summer Pascal, Utah 52-70, FFVA
2-13 and Fla. 683. These data are given in more detail since several of the
differences in the chemical data between the two selections, FFVA 2-13 and
Fla. 683, both selections from Utah 52-70, were highly significant and of
interest. Boron and manganese were applied in the broadcast fertilizer mix
at 7.2 Ibs. B ,0 and 10.0 Ibs. MnO per acre, an increase in soil boron appli-
cations over the former experiments.
Table 8. Total weight in pounds per 20 feet of row of celery varieties and
pH at Summer Utah FFVA Fla.
Harvest Pascal 52-70 2-13 683
6.24 97 124 124 128
5.53 95. 119 123 122
5.20 98 114 117 119
Summer Pascal growth as in the previous experiments seemed little
affected by pH adjustment, whereas Utah 52-70 and the Florida selections
significantly decreased with decreasing pH. Boron spray treatments did not
increase yields in this experiment.
Table 9. Percent of plants with blackheart.
Blackheart percentages increased with decreasing pH. Summer Pascal was
the most affected. Fla. 683 had significantly less blackheart than FFVA 2-13.
Number of cracked petioles on 30 plants.
Both pH effects and variety differences were highly significant. Boron
sprays decreased rib .cracking at the higher pH level but not at the two lower
Table 11. Phosphorus content of outer rib tissue, percent of dry weight.
The Utahs contained significantly higher P than Summer Pascal, and Fla.
683 more phosphorus than FFVA 2-13.
The difference in the magnitude of the calcium found in the samples
tabulated below, and the former experiments was due to the location on the
plant of the samples taken. The former samples were taken from flairing outer
ribs just before harvest. The following data were taken from outer rib samples
remaining after field trimming during harvest. The ribs are younger than those
of the former experiment. Consequently, calcium content is in a lower range.
The important point, however, is the differences found between treatments and
varieties within each experiment.
Table 12. Calcium content of outer rib tissue, percent of dry weight.
Calcium content of petiole tissue was higher for the Utahs, and Fla. 683
contained more calcium than FFVA 2-13.
Manganese content of outer rib tissue, parts per million dry weight.
Data are given from unsprayed treatments only.
Utahs contained more manganese than Summer Pascal, Fla. 683
in manganese than 52-70 or FFVA 2-13.
Boron content of outer rib tissue, parts per million dry weight,
unsprayed treatments only.
Summer Pascal contained more boron than the Utahs, Fla. 683 more than
3. Soil reaction effects on escarole.
The following data are taken from a factorial pH x P x K experiment with
escarole. Only the pH data are given here. Boron equivalent to 10 lbs. borax
per acre (3.6 lbs. B203) and 30 lbs. manganese sulfate (10 lbs. MnO) per acre
were used uniformly in the fertilizer mix. Each fertilizer and pH plot was
split and five weekly applications of 1.0 lb. MnSO4 (32.5% Mn) in 100 gallons
of water were applied as nutritional sprays on one half of each fertilizer
plot with the following results:
Harvest weights and color ratings of pH and manganese spray treat-
ments on escarole.
Total weight per plot
Check Mn spray
Color rating at harvest*
Check Mn spray
*1 = poor to 4 = excellent
An outer leaf for chemical analysis was taken from each of several plants
after trimming to a marketable plant. Data below are from non-sprayed plots
Table 16. Chemical analysis of outer leaf tissue.
D. Some vegetable crop responses to manganese and boron (mostly from Special
Bulletin 425, Michigan State University Agricultural Experiment Station).
Chicory & Endive
Crops with a high requirement for manganese will respond to S or 6 sprays
of 2 Ibs. manganese sulfate applied weekly where the pH is 6.0 and higher; MnO
dusts are effective but wasteful of material and not as effective as sprays.
Sprays containing manganese as salts of the ethylene bisdithiocarbamates
(Maneb, ManZate, M-22, etc.) used as fungicides are effective in supplementary
foliar manganese nutrition. If used frequent enough, they may supply all of
the manganese required for the supplementary manganese requirement.
Crops with a high requirement for boron may respond to 5 or 6 nutritional
sprays containing 2 lbs. Solubor (20%B) per 100 gallons of water where the
soil pH is above 6.0. Boron sprays may decrease yield where the soil is 5.5
From the data presented above, one would expect that if sampling was done
before plowing and the pH was about 6.0 or slightly above, conditions for good
manganese nutrition would be present as the crop matured.
The large increase in phosphorus availability as the pH was lowered
indicates that available phosphorus might be alarmingly high on presently
highly fertilized high pH soil if the pH were lowered 0.5 pH units or more.
The data indicate that boron becomes less available as the pH increases
in organic soils within the ranges used here. This is indicated in the second
field celery pH experiment. The increase in calcium uptake by the plant at the
higher pH values may have resulted in a higher boron requirement by the plant
which becomes acute in high boron requiring plants.
Crop differences in response to nutritional conditions are well known and
fertilizers are applied accordingly. Variety and type differences within crops
are generally not as well recognized, .
Understandably, plant breeders have been highly concerned with disease
resistance, market types, appearance and adaptability to prevailing conditions
and have given little thought to selection for nutritional factors.
Significant differences in celery varieties between the Summer Pascal and
the Utah variety and particularly between FFVA 2-13 and Fla. 683 selected from
the Utah variety, indicate the variability to many nutritional factors is
present in celery for selection. The differences between these selections
from Utah 52-70 are probably not the extremes found within the commercial line.
This is also clearly demonstrated in sweet corn hybrids. Some are known
to be more sensitive to zinc deficiencies than others. Silver Queen, Winter
Garden and Winter Green are more sensitive to manganese availability as
affected by soil pH than lobelle and most other sweet corn hybrids.
At least one variety of escarole exhibits severe magnesium deficiencies
in 25% of its population when planted on some of our organic soil areas.
This ratio always remains constant.
In crops whose seed is normally cross pollinated or partially cross
pollinated one might expect these ordinarily hidden types of variabilities to
occur. The introduction of new germplasm, particularly from foreign intro-
ductions, would certainly tend to increase this type of variability