• TABLE OF CONTENTS
HIDE
 Title Page
 Credits
 Table of Contents
 Fig. 2 and 3
 Introduction
 Scope of experiment
 Plan of experiment
 Precipitation
 Crop conditions in experimental...
 Cultivation of experimental...
 Fertilizers
 Effects of cover crops on growth...
 Nut sizes and kernel percentag...
 Effects of cover crops on orchard...
 Effects of cover crops on...
 Discussions and recommendation...
 Summary
 Literature cited














Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; no. 297
Title: A cover crop program for Florida pecan orchards
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027269/00001
 Material Information
Title: A cover crop program for Florida pecan orchards
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 44 p : ill., charts ; 23 cm.
Language: English
Creator: Blackmon, G. H ( Gulie Hargrove ), 1886-
Barnette, R. M
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1936
 Subjects
Subject: Pecan -- Florida   ( lcsh )
Cover crops -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 44.
Statement of Responsibility: by G.H. Blackmon and R.M. Barnette.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station)
 Record Information
Bibliographic ID: UF00027269
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000924375
oclc - 18277503
notis - AEN4993

Table of Contents
    Title Page
        Page 1
    Credits
        Page 2
    Table of Contents
        Page 3
    Fig. 2 and 3
        Page 4
    Introduction
        Page 5
        Page 6
    Scope of experiment
        Page 7
        Page 8
    Plan of experiment
        Page 9
        Page 10
    Precipitation
        Page 11
    Crop conditions in experimental orchard
        Page 11
        Page 12
    Cultivation of experimental area
        Page 13
        Page 14
        Page 15
    Fertilizers
        Page 16
        Page 17
        Page 18
    Effects of cover crops on growth and yield of pecan trees
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
    Nut sizes and kernel percentages
        Page 26
        Page 27
        Page 28
        Page 29
    Effects of cover crops on orchard returns
        Page 30
        Page 31
    Effects of cover crops on the soil
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
    Discussions and recommendations
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
    Summary
        Page 43
    Literature cited
        Page 44
Full Text



Bulletin 297


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA
WILMON NEWELL, Director






A COVER CROP PROGRAM

FOR FLORIDA PECAN ORCHARDS


By G. H. BLACKMON and R. M. BARNETTE


Fig. 1.-Austrian peas in Plot 1 of the Frotscher pecans.


Bulletins will be sent free to Florida residents upon application to
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA


May, 1936


*! `-y









EXECUTIVE STAFF
John J. Tigert, M.A., LL.D., President of
the University
Wilmon Newell, D.Sc., Director
H. Harold Hume, M.S., Asst. Dir., Research
Harold Mowry, M.S.A., Asst. Dir., Adm.
J. Francis Cooper, M.S.A., Editor
Jefferson Thomas, Assistant Editor
Clyde Beale, A.B.J., Assistant Editor
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Manager
K. H. Graham, Business Manager
Rachel McQuarrie, Accountant

MAIN STATION, GAINESVILLE

AGRONOMY
W. E. Stokes, M.S., Agronomist*
W. A. Leukel, Ph.D., Agronomist
G. E. Ritchey, M.S.A., Associate*
Fred H. Hull, Ph.D., Associate
W. A. Carver, Ph.D., Associate
John P. Camp, M.S., Assistant
ANIMAL HUSBANDRY
A. L. Shealy, D.V.M., Animal Husbandman**
R. B. Becker, Ph.D., Dairy Husbandman
W. M. Neal, Ph.D., Asso. in An. Nutrition
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarian
N. R. Mehrhof, M.Agr., Poultry Husbandman
W. W. Henley, B.S.A., Asst. An. Husb.*
W. G. Kirk, Ph.D., Asst. An. Husbandman
R. M. Crown, M.S.A., Asst. An. Husbandman
P. T. Dix Arnold, B.S.A., Assistant Dairy
Husbandman
L. L. Rusoff, M.S., Laboratory Assistant
Jeanette Shaw, M.S., Laboratory Technician
CHEMISTRY AND SOILS
R. W. Ruprecht, Ph.D., Chemist**
R. M. Barnette, Ph.D., Chemist
C. E. Bell, Ph.D., Associate
R. B. French, Ph.D., Associate
H. W. Winsor, B.S.A., Assistant
ECONOMICS, AGRICULTURAL
C. V. Noble, Ph.D., Agricultural Economist"
Bruce McKinley, A.B., B.S.A., Associate
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Assistant
ECONOMICS, HOME
Ouida Davis Abbott, Ph.D., Specialist**
C. F. Ahmann, Ph.D., Physiologist
ENTOMOLOGY
J. R. Watson, A.M., Entomologist**
A. N. Tissot, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
HORTICULTURE
A. F. Camp, Ph.D., Horticulturist**
G. H. Blackmon, M.S.A., Horticulturist and
Associate Head of Department
A. L. Stahl, Ph.D., Associate
F. S. Jamison, Ph.D., Truck Horticulturist
R. J. Wilmot, M.S.A., Specialist, Fumigation
Research
R. D. Dickey, B.S.A., Assistant Horticulturist
PLANT PATHOLOGY
W. B. Tisdale, Ph.D., Plant Pathologist**
George F. Weber, Ph.D., Plant Pathologist
R. K. Voorhees, M.S., Assistant***
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Assistant Botanist
Stacy O. Hawkins, M.A., Assistant Plant
Pathologist
SPECTROGRAPHIC LABORATORY
L. W. Gaddum, Ph.D., Biochemist
L. H. Rogers, M.A., Spectroscopic Analyst


BOARD OF CONTROL
Geo. H. Baldwin, Chairman, Jacksonville
Oliver J. Semmes, Pensacola
Harry C. Duncan, Tavares
Thomas W. Bryant, Lakeland
J. T. Diamond, Secretary, Tallahassee


BRANCH STATIONS
NORTH FLORIDA STATION, QUINCY
L. 0. Gratz, Ph.D., Plant Pathologist in
Charge
R. R. Kincaid, Ph.D., Asso. Plant Pathologist
J. D. Warner, M.S., Agronomist
Jesse Reeves, Farm Superintendent
CITRUS STATION, LAKE ALFRED
A. F. Camp, Ph.D., Horticulturist in Charge
John H. Jefferies, Superintendent
W. A. Kuntz, ALM., Assoc. Plant Pathologist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson, B.S., Asst. Entomologist
EVERGLADES STATION, BELLE GLADE
A. Daane, Ph.D., Agronomist in Charge
R. N. Lobdell, M.S., Entomologist
F. D. Stevens, B.S., Sugarcane Agronomist
Thomas Bregger, Ph.D., Sugarcane Physiologist
G. R. Townsend, Ph.D., Assistant Plant
Pathologist
J. R. Neller, Ph.D., Biochemist
R. W. Kidder, BS., Assistant Animal
Husbandman
Ross E. Robertson, B.S., Assistant Chemist
B. S. Clayton, B.S.C.E., Drainage Engineer*
SUB-TROPICAL STATION, HOMESTEAD
H. S. Wolfe, Ph.D., Horticulturist in Charge
W. M. Fifield, M.S., Asst. Horticulturist
Geo. D. Ruehle, Ph.D., Associate Plant
Pathologist
W. CENTRAL FLA. STA., BROOKSVILLE
W. F. Ward, M.S.A., Asst. An. Husbandman
in Charge*


FIELD STATIONS

Leesburg
M. N. Walker, Ph.D., Plant Pathologist in
Charge
W. B. Shippy, Ph.D., Asso. Plant Pathologist
K. W. Loucks, M.S., Asst. Plant Pathologist
J. W. Wilson, Ph.D., Associate Entomologist
Plant City
A. N. Brooks, Ph.D., Plant Pathologist
Cocoa
A. S. Rhoads, Ph.D., Plant Pathologist
Hastings
A. H. Eddins, Ph.D., Plant Pathologist
Monticello
G. B. Fairchild, M.S., Asst. Entomologist***
Bradenton
David G. Kelbert, Asst. Plant Pathologist
C. C. Goff, M.S., Assistant Entomologist
Sanford
E. R. Purvis, Ph.D., Assistant Chemist,
Celery Investigations
Lakeland
E. S. Ellison, Ph.D., Meteorologist*
B. H. Moore, A.B., Asst. Meteorologist*

In cooperation with U.S.D.A.
** Head of Department.
*** On leave.

















CONTENTS
Page
SCOPE OF THE EXPERIMENT....-.............---------- ----- --------..----.. .-- ---... 7
PLAN OF EXPERIMENT-.......................--.. ----.--------- -----------...... ----.---. 9
PRECIPITATION .......... ....... .....------------------ ---- -------- 11
CROP CONDITIONS IN EXPERIMENTAL ORCHARD......... ..------.....------- 11
CULTIVATION OF EXPERIMENTAL AREA.....-...--.--- ................ 13
FERTILIZERS ................ .......... --.......-- 16
GREEN MANURE .................... -.......--- -- --- -------------.------- -- --------- 16
EFFECTS OF COVER CROPS ON GROWTH AND YIELD OF PECAN TREES ............... 19
Grow th..-............................- .... -- .... 19
Yields .......... ..-- ... ......... ... ..... ........---..- ------ --.- ..... 20
NUT SIZES AND KERNEL PERCENTAGES -....--............. -------. -- 26
Frotscher ......................... .............................. .... ... 27
Stuart....................... ... ..... ..... ...- ..... .. ....27
EFFECTS OF COVER CROPS ON ORCHARD RETURNS .....--..-...- ....- .......... 30
EFFECTS OF COVER CROPS ON THE SOIL -.............. ........ --------------32
Tube Samples--..... --....-..--.- ----------. -----------. 32
Soil Reaction.......... ..-....- -------- -------34
Nitrogen ............------------- -- --- ---------------.... -- ------------. 34
Organic Matter ................ ------- -- ---------36
Volume Samples ........----- -------- -- -------------......- ---... ----------- 37
Nitrogen...............----.-........--. ....- --.- --------------. 37
Organic Matter ..............-..--..-..-.. --- ---- ------------ 37
Sudan Grass Growth ...-.. ---.......----------..... 37
DISCUSSION AND RECOMMENDATIONS ............. .. -----... --- 38
SUM M ARY .............. ... ... .- ..... ........... -- --- ----... 43
LITERATURE CITED ...... .. .............. ........-. -- ..--. ....... 44





































Fig. 2.-Frotscher block three years before the cover-crop experiment
was started.


Fig. 3.-The Stuart block three years before the cover-crop experiment
was started.









A COVER CROP PROGRAM

FOR FLORIDA PECAN ORCHARDS

By G. H. BLACKMON and R. M. BARNETTE

The pecan is indigenous to the United States and Mexico,
being found in great abundance along the lower Mississippi
River and its tributaries and the water courses of Texas and
northern Mexico. The soils of those areas are fertile and well
drained. Silt in large quantities is deposited evenly over such
lands when covered with flood waters, adding much available
plant food, and is an important factor in maintaining soil fertility
in these regions.
Since pecan dissemination and cultivation began, many plant-
ings have been made in Florida on soils quite different from
those where pecan trees are indigenous. Consequently, many
orchards have been unproductive largely because of variety and
soil factors. (While varieties will not be discussed in this bul-
letin, they must be adapted to Florida conditions or they will
not respond to a soil improvement program.) However, with
the right varieties growing on suitable soils it is possible to
maintain a cultural program that will produce thrifty trees and
profitable production of nuts.
It has been pointed out by Isbell (8)1, Crane (4), and others
(5) and (7), that pecan trees must produce proper twig growth
to insure adequate yields. One of the great problems facing
Florida growers is that of maintaining sufficient growth in old
trees to give abundant nut production. It seems, however, that
trees can be made to produce adequate growth if a suitable fer-
tilizing and cultural program is practiced.
Skinner and Demaree (10), working with pecans on Norfolk
fine sandy loam soils in southern Georgia, found that satisfactory
tree growth could be obtained by the addition of sufficient quan-
tities of organic materials in the form of either stable manure
or leguminous cover crops. Frotscher trees increased in per
acre production during the six years of the experiment from
14 to 576 pounds and Moneymaker from nothing to 530 pounds.
1 Italic figures in parentheses refer to "Literature Cited" in the back
of this bulletin.
Acknowledgments:-The authors wish to express their thanks to Agron-
omist W. E. Stokes for suggestions and cooperation in testing prospective
cover crops; and to H. K. Miller, who permitted the use of part of his
orchard and willingly cooperated in conducting the experiment.







Florida Agricultural Experiment Station


Stuart trees on deep sandy loam soil in Mississippi responded
favorably to Crotalaria striata as a summer cover crop (9).
The increased yield where the crotalaria was grown over the
non-legume plot amounted to 180 and 540 pounds of nuts per
acre, respectively, in 1930 and 1931.2
Crotalaria spectabilis,s however, proved to be the outstanding
summer legume for pecan orchards in Florida, especially before
the trees attained size sufficient to shade most of the ground (2).
It was adaptable to an all cover-crop system or in connection
with inter-crops of corn.
Pecan trees above the average in thrift and production are
commonly observed about home grounds and at favorable loca-
tions in the orchard. These trees are of more than passing
interest because they are living examples of the results of favor-
able moisture and plant food conditions. Orchards in which
poor twig growth and light nut production are obtained are
those located on soils low in available plant foods. Under such
conditions it is impossible for trees to make satisfactory growth
and adequate yields. Commercial fertilizers alone failed to pro-
duce profitable yields of Frotscher and Stuart on Norfolk sandy
loam and Norfolk fine sandy soils, respectively, in pecan fertilizer
experiments in Florida (3).
In 1924 and thereafter cover crops were included in the
Florida pecan experiments to test their value as a means toward
improving soil conditions and increasing the yields of old estab-
lished orchards. In the beginning the work was confined en-
tirely to the testing of various plants that could be grown as
soil improving crops. As a result of repeated trials Austrian
peas and hairy vetch were established as the most outstanding

2 Effects of cover crops on growth and yield of Pineapple oranges and
corn in Florida are reported in (11) and (12).
3Crotalaria spectabilis is toxic to livestock and poultry, according to
investigations conducted by the Animal Husbandry Department of this
Station. It should be thoroughly disked into the soil before animals are
turned into orchards and fields where it has been grown. There are other
species, however, which are not toxic so far as is known at present, and
apparently these can be grown safely where livestock are grazed. For
information on this subject see the following publications:
BECKER, R. B., W. M. NEAL, P. T. DIX ARNOLD and A. L. SHEALY. A Study
of the Palatability and Possible Toxicity of 11 Species of Crotalaria,
Especially of C. spectabilis Roth. Journal of Agricultural Research
50: 11: 911-922. 1935.
NEAL, W. M., L. L. RUSOFF and C. F. AHMANN. The Isolation and Some
Properties of an Alkaloid from Crotalaria spectabilis Roth. Journal
of the American Chemical Society 57: 2560. 1935.
THOMAs, E. F., W. M. NEAL and C. F. AHMANN. The Toxicity of Crota-
laria spectabilis Roth. to Livestock and Poultry. Journal of the
American Society of Agronomy 27: 6. 1935.







A Cover Crop Program for Florida Pecan Orchards 7

winter legumes and oats and rye as the best winter non-legumes
for Florida conditions (1).
Augusta vetch, Vicia angustifolia, gives promise as a winter
legume (although it was not used in the cover crop experiment)
since it has reseeded for a number of years in small areas in
an orchard at Starke and another at Baldwin and along the
streets and highways in and around Tallahassee. It has been
noted also growing in small patches at Monticello, Quincy, and
Marianna. Doubtless it could be found in other locations in
northwest Florida. A few scattering plants were grown suc-
cessfully over a small area in the pecan variety orchard at
Gainesville in 1934-1935. It will not give very satisfactory
results, however, if there is not a quantity of organic material
in or on the surface of the soil, and if the soil is not of good
type. In neglected orchards in which livestock is being run, it
should prove of considerable value because it seems to have ex-
cellent qualities as a grazing legume. Seed of Augusta vetch
has been difficult to obtain in past years, but it is hoped that
in the near future it will be available at Florida seed houses.
Winter legumes require inoculation when planted on lands
where they have not been previously grown. This inoculation
can be made with commercial cultures which may be secured
from seed houses, or soil can be used from nearby land on which
vetch and peas have been successfully grown for several years.
Soil used for inoculating purposes should be spread by evenly
distributing a very thin layer over the new field at the time
the seed are planted. Commercial materials carry directions
printed on the package. In the Jefferson County experiment
discussed in this bulletin, good results were obtained by inocu-
lating seed with a commercial product at the time of planting.

SCOPE OF EXPERIMENT
This experiment was started in 1927 to determine the effects
of cover crops and fertilizers on the growth and yield of pecans.
Information was desired also on the value of different soiling
crops, such as: The growing of legumes in winter and summer
versus combinations of non-legumes in winter and legumes in
summer; the effects of applications of nitrogenous fertilizers on
the trees if legumes were grown. Consequently winter legumes
and non-legumes were grown and followed by summer legumes
in the different plots, and an area was left unplanted as a check.
This was fertilized the same as the planted plots. Sulfate of








Florida Agricuttural Experiment Station


Fig. 4.-Hairy vetch in Frotscher Plot 2.


Fig. 5.-Oats in Frotscher Plot 4, just before the land was disked in
the spring.







A Cover Crop Program for Florida Pecan Orchards 9

ammonia was applied annually in June or July to half of each
plot beginning with 1930. This was done for the purpose of
testing its effects on tree growth and yield when used on soils
under different cover-crop management. Superphosphate and
sulfate of potash were applied to all plots annually in the fall.
The block of Frotscher (Fig. 2) and Stuart (Fig. 3) selected
for the tests is located in Jefferson County. The land is only
slightly rolling with no appreciable erosion and is classified as
Norfolk fine sandy loam. This type is commonly planted to
pecans in the area. The trees were set 17 to the acre in 19044
and were therefore 23 years old when the experiment was
initiated in 1927. They were rather uniform, although they had
been in low production for several years prior to 1927 when there
were no planted cover crops grown and little or no fertilizers
applied.
PLAN OF EXPERIMENT
After it had been determined which winter and summer cover
crops would make best growth, the experiment was planned to
test their value in pecan orchards. The work was started in
1927. In the experimental area were 144 trees planted 50 by 50
feet, but records were kept on the behavior of only 42 Frotschers
and 42 Stuarts, the others being used as buffers between the
cover-crop plots.
The block of trees was divided into four plots for each variety,
three planted to cover crops and one used as a check where
nothing was planted. The planted plots each contained 12
Frotscher and 12 Stuart trees originally, and the unplanted plot
six of each variety. In 1930 all plots were divided equally into
two sections, A and B; with this arrangement there were six
trees of each variety in the corresponding parts of the planted
plots and three in the unplanted. Austrian peas (Fig. 1), hairy
vetch (Fig. 4), and oats (Fig. 5) were grown on the cover-
cropped Plots 1, 2 and 4 during the winter and C. spectabilis
during the summer. No crops were planted on Plot 3 either
winter or summer (Figs. 6 and 7). The following amounts of
seed in pounds per acre were planted annually in the experiment:
Hairy vetch 20, Austrian peas 30, oats 64, rye 60, and C. spec-
tabilis 6 each in 1928 and 1931 only, as it volunteer all other
years. The initial planting of the cover crops was made in 1927
and growth and yield records started in 1928.

4 This date was given as 1908 in former published articles.








Florida Agricultural Experiment Station


Fig. 6.-Native summer vegetation in unplanted Stuart Plot 3, the first
year of the experiment.


Fig. 7.-Native winter vegetation in unplanted Frotscher Plot 3 just before
the land was disked in the spring. Stuart trees in background.







A Cover Crop Program for Florida Pecan Orchards 11

At the beginning and again in 1933 soil samples were taken
for three depths at definite locations in each plot where no sul-
fate of ammonia was applied. From the same places volume
samples averaging about 10 pounds each were taken in 1934.

PRECIPITATION
The rainfall at Monticello as recorded by the U. S. Weather
Bureau for 1927 to 1934 is shown in Table 1. These data are
presented as information only, as no attempt was made to de-
termine the effect of precipitation on growth and yield of pecans.
The rain gage of the U. S. Weather Bureau was located about
200 yards from the orchard in which the experiment was con-
ducted until August 1, 1930, when it was moved to another farm
about one mile to the southwest.

CROP CONDITIONS IN EXPERIMENTAL ORCHARD
The trees selected for the test were low in vigor when the
work was started in 1927. The 1928 production was preceded
by several years of no yields or at least light ones, and was
immediately followed by one failure and two light crops (Table
4). Similar yields are quite common with bearing trees low
in vitality and making poor growth.
It should be pointed out that yields throughout the experiment
would have been much higher if insects had not taken heavy
tolls, as both leaf and nut case-bearers caused severe damage.
It was interesting to observe in the spring of 1931 that the
Frotscher trees where legumes were grown during both winter
and summer had stored a sufficient food reserve in the twigs
to force a heavy pistillate bloom after the original terminal
buds had been destroyed by the leaf case-bearer. However, the
staminate bloom, forced at the normal time, was extremely light
due to damages caused by this insect; therefore there was a
shortage of pollen during the critical period of pollination which
resulted in a light Frotscher yield in 1931.
As a result of the 1931 drouth and the subsequent warm
winter and consequent delayed dormancy of the trees, together
with the severe freeze in March of 1932, again there was a very
light crop produced by the Stuart. The trees were extremely
late and irregular in forcing growth and had a very light bloom
in 1932, and were not in full leaf until well into June, all of
which contributed materially to the very low production for that
year. The Frotscher trees, however, were not so severely upset







A Cover Crop Program for Florida Pecan Orchards 11

At the beginning and again in 1933 soil samples were taken
for three depths at definite locations in each plot where no sul-
fate of ammonia was applied. From the same places volume
samples averaging about 10 pounds each were taken in 1934.

PRECIPITATION
The rainfall at Monticello as recorded by the U. S. Weather
Bureau for 1927 to 1934 is shown in Table 1. These data are
presented as information only, as no attempt was made to de-
termine the effect of precipitation on growth and yield of pecans.
The rain gage of the U. S. Weather Bureau was located about
200 yards from the orchard in which the experiment was con-
ducted until August 1, 1930, when it was moved to another farm
about one mile to the southwest.

CROP CONDITIONS IN EXPERIMENTAL ORCHARD
The trees selected for the test were low in vigor when the
work was started in 1927. The 1928 production was preceded
by several years of no yields or at least light ones, and was
immediately followed by one failure and two light crops (Table
4). Similar yields are quite common with bearing trees low
in vitality and making poor growth.
It should be pointed out that yields throughout the experiment
would have been much higher if insects had not taken heavy
tolls, as both leaf and nut case-bearers caused severe damage.
It was interesting to observe in the spring of 1931 that the
Frotscher trees where legumes were grown during both winter
and summer had stored a sufficient food reserve in the twigs
to force a heavy pistillate bloom after the original terminal
buds had been destroyed by the leaf case-bearer. However, the
staminate bloom, forced at the normal time, was extremely light
due to damages caused by this insect; therefore there was a
shortage of pollen during the critical period of pollination which
resulted in a light Frotscher yield in 1931.
As a result of the 1931 drouth and the subsequent warm
winter and consequent delayed dormancy of the trees, together
with the severe freeze in March of 1932, again there was a very
light crop produced by the Stuart. The trees were extremely
late and irregular in forcing growth and had a very light bloom
in 1932, and were not in full leaf until well into June, all of
which contributed materially to the very low production for that
year. The Frotscher trees, however, were not so severely upset








TABLE 1.-MONTHLY AND ANNUAL PRECIPITATION AT MONTICELLO, FLORIDA, FOR THE YEARS 1927 TO 1934, INCLUSIVE, WITH
DEPARTURES FROM THE NORMAL.
1927 1928 I 1929 1930 1931 1932 1933 1934
0 0 0 0 c 00' o




January ......................... 0.10 -4.00 1.11 -2.99 5.94 +1.84 6.52 2.42 4.40 0.2 5.36 +1.24 6.56 +2.44 1.27 -2.85
February .... .... -00 .13 +. 44.36 0.40 2.41 -1.7 1.27 -2.95 7.60 +3.38 3.78 -0.44

April............................ 0.35 -3.11 9.21 +5.75 7.92 +4.46 1.93 -1.53 -2.2 2.54 -1.17 +3.32 2.42 1.29

January............................... 1.37 -4.00 1.11 0.66 8.94 +4.04 6.52 +2.42 4 -3.2 5.31 +1.13 2.02 -2.16 8.26 +4.08
Juneb............................... 9.46 +3.11 9.27 +2.92 7.44 0 4.07 -2.28 0.67 -51.7 1.727 2.18 7.60 +- .38 3.98 -0.44
March............................... .13 -0.92 8.28 +5.23 6.57 +-0.18 6.63 +3.58 5.584.59 6.22 -.91 10 6.9802 4.1 0.55

Aprilugust..........................6.77 +0.43 9.21 +5.75 7.92 +4.46 1.93 -1.53 1.4 1.4 2.54 -1.1 7.03 +3.32 2.42 -1.29




September.................... 1.81 3.63 9.60 +4.16 8.82 +3.38 6.33 +0.89 1.31 4.2 9.70 +3.84 3.49 -2.37 2.82 -3.04
October..... ... ...... 1.77 -1.03 1.67 -1.13 4.51 +1.71 0.64 -2.161 1.06 1.62 4.15 +1.40 0.12 -2.63 2.22 -0.53
November.............. 0.94 1.17 1.57 -0.54 0.765 1.35.12.48 +10.37 -2.45 4.46 +1.87 0.93 -1.66 2.42 -0.17
December......................... 4.29 -1.10 2.86 -2.53 2.82 -2.57 3.69 -1.70 4.42 -0.50 1.82 -2.91 0.86 -3.87 0.94 -3.79

Annual..................... 37.33 16.90 86.47 +32.2470.83 +16.60 62.89 +8.66 37.67 -18.28 61.24 +4.98 51.11 -5.15 51.25 -5.01

Sept Less than .01 inch. N = 54.23 in '27, '28, '29, '30; 55.95 in '31; 56.26 in '32, '33, '34.
T==Less than .01 inch. N =54.23 in '27, '28, '29, '30; 55.95 in '31; 56.26 in '32, '33, '34.







A Cover Crop Program for Florida Pecan Orchards 13

by these conditions and produced a moderately good crop of nuts
in 1932, which was heavier in corresponding parts of the planted
plots than where no cover crops were grown. Yet, under these
adverse conditions the data in Table 4 show that trees in the
plots where the winter and summer legumes had been grown
and returned to the soil for four years gave the highest pro-
duction.
The majority of Stuart trees in the experiment developed
varying amounts of rosette after the experiment was started,
doubtless reducing yields of this variety to a marked degree.
While this condition contributed materially to the low produc-
tion, it probably was not the sole cause, as trees of the Stuart
variety did not respond to fertilizers in other experiments (3)
as satisfactorily as some other varieties. The rosette, however,
was not caused by treatments given to any of the plots, as it was
general and could be traced to other factors operating prior to
the period of the experiment.

CULTIVATION OF EXPERIMENTAL AREA
All plots were cultivated by either disking or shallow plowing
each fall in preparation for planting winter cover crops. The
soil was again disked each spring except in years when there
was an exceptionally heavy growth of winter crops; at such
times the plants were allowed to die down and form a mulch
over the soil, and no cultivation at all was given to any of the
plots. The heaviest mulch was made by hairy vetch, the second
heaviest by Austrian peas, while the oat mulch was almost as
scanty as the covering produced by the native growth of weeds
and grasses in the check plots. The hairy vetch was very dense
in 1931, giving a mulch so completely covering the surface of
the soil that even the growth of nut grass was materially re-
tarded. However, the C. spectabilis, due to a thin stand of
plants, made a poor showing during the summers when the land
was left uncultivated in the spring.
Cultivation was handled in this manner because it seemed
better to have a mulch on the land whenever possible rather
than to clean cultivate the area; in so doing it was necessary
to leave the check and non-legume plots undisturbed so that the
soil would receive the same treatment in all plots. This pro-
cedure proved to be extremely beneficial for the hairy vetch
plot, but it was not so advantageous in the non-legume and check
plots and for the growth of the summer legume.












TABLE 2.-ANNUAL AND TOTAL AMOUNT OF ORGANIC MATERIAL PRODUCED BY THE COVER CROPS AND THE NITROGEN RE-
TURNED TO THE SOIL BY THE LEGUMES (TOPS ONLY) IN THE PECAN EXPERIMENT.


Cover Crop



Austrian peas .................
C. spectabilis .................

Hairy vetch .......................
C. spectabilis ................

Check--Unplanted,
light growth of
native vegetation.

Oatst ....... ........
C. spectabilis ............ ....
Hairy vetcht .................


When
Grown


Winter
Summer

Winter
Summer




Winter
Summer
Winter


Dry
Matter
Avg. *
Percent

18.8
28.6

18.2
28.6




26.0
28.6
18.2


Nitro-
gen -
Avg.*
Percent

2.15
1.45

3.10
1.45




1.05
1.45
3.10


Pounds per Acre of Organic Material Grown and Returned
to the Soil


1928
Green Dry**


16,532
6,316

13,503
6,534





6,534
13,400


3,108
1,806

2,457
1,869


Green

15,681
***

7,840
***


Dry**

2,948

1,427


Plot



1

2


3


4


1930
Green I Dry**

4,791 901
7,100 2,031

1,000 182
13,500 3,861


500
14,100


130
4,033


1931
Green Dry**

20,000 3,760
2,500 715

32,000 5,824
3,000 858


1,000
3,000


260
858


Averages of numerous analyses of materials (oven dry) grown at Gainesville, made by the Department of Chemistry
and Soils over a period of years, and not of samples taken from the pecan experiment.
** Calculated from the oven dry percentages.
*** Crotalaria was not weighed in 1929.
t Rye was grown in 1928-29 and 1929-30.
: Hairy vetch was grown for general comparison in Plot 4 the first winter of the experiment, 1927-28.


775 202
1,869 *** .....
2,439 ............









TABLE 2.-ANNUAL AND TOTAL AMOUNT OF ORGANIC MATERIAL PRODUCED BY THE COVER CROPS AND THE NITROGEN RE-
TURNED TO THE SOIL BY THE LEGUMES (TOPS ONLY) IN THE PECAN EXPERIMENT. -Continued.
Pounds per Acre of Organic Material Grown and
Returned to the Soil Pounds of Nitrogen per Acre Returned to the
Plot e3 t3 te So Soil by the Legumes**
1932 I 1933 1 1934 I Total _____ ___ _
Green Dry** Green Dry** Green | Dry** Green I Dry** 1928 1929 1930 1931 1932 1933 1934 Total

1 2,000 376 7,500 1,410 8,000 1,504 74,504 14,007 66.8 63.4 19.4 80.8 8.1 30.3 32.3 301.1
1,500 429 1,500 429 8,494 2,429 27,410 7,839 26.2 ........ 29.4 10.4 6.2 6.2 35.2 113.6
2 8,000 1,456 9,000 1,638 10,000 1,820 81,343 14,804 76.2 44.2 5.6 180.5 45.1 50.8 56.4 458.8
1,200 343 1,500 429 9,147 2,616 34,881 9,976 27.1 ........ 56.0 12.4 5.0 6.2 37.9 144.6
3


4 500 130 1,000 260 3,000 780 6,775 1,762 ............ ... -. ...... ...... ....
2,500 715 2,500 715 10,272 2,938 38,906 11,128 27.1 -..... 58.5 12.4 10.4 10.4 42.6 161.4
.... 13,400 2,439 75.6 .......... ......... ....... ... ............ ......... 75.6

Averages of numerous analyses of materials (oven dry) grown at Gainesville, made by the Department of Chemistry
and Soils over a period of years, and not of samples taken from the pecan experiment.
** Calculated from the oven dry percentages.
*** Crotalaria was not weighed in 1929.
t Rye was grown in 1928-29 and 1929-30.
t Hairy vetch was grown for general comparison in Plot 4 the first winter of the experiment, 1927-28.






16 Florida Agricultural Experiment Station

FERTILIZERS
In experiments at the Florida Station (12), results of which
were not published until 1932, hairy vetch and Austrian peas
gave best results when grown on land that received applications
of superphosphate. Hence it was planned to apply superphos-
phate in the fall to Plots 1 and 2 in which the two winter legumes
were to be grown. Pecan experiments by this Station indicated
that when grown on Norfolk fine sandy loam soil, trees should
receive potash in the fertilizers.
Consequently, it was decided to fertilize the experimental
block with both phosphate and potash, and these materials were
applied to all plots for uniformity. Both were applied in the fall,
since the phosphate was needed for the cover crops at that time
and the potash did not leach materially and could be conveniently
applied with the phosphate.
Applications of superphosphate and sulfate of potash were
made broadcast just before or at the time the winter crop was
seeded. Total amounts applied per acre annually were 300
pounds of 16% superphosphate and 60 pounds of sulfate of
potash. From 1930 until 1934, the B section of each plot re-
ceived in addition annual applications of sulfate of ammonia at
the rate of 340 pounds per acre applied broadcast over the soil
during June or July.

GREEN MANURE
Plots by number, cover crops grown in each with total and
annual amounts of green material, calculated oven-dry matter,
and nitrogen returned to the soil by the legumes are listed in
Table 2. In considering the tonnage of green material it should
be pointed out that Crotalaria spectabilis did not make maximum
growth because the large trees shaded the land almost com-
pletely during the growing season, making it impossible for
the plants to receive adequate light. Therefore the amount of
green manure returned to the soil by this crop was lower than
it would have been in orchards of smaller trees where the sun-
light could have reached the entire area.
The data in Table 2 show that the greatest amount of green
material was returned to the soil by hairy vetch and C. spectabilis
in Plot 2, with the growth of Austrian peas and C. spectabilis
in Plot 1 almost as heavy. Plot 4, in which the winter non-
legumes and a summer legume were grown, gave the heaviest






A Cover Crop Program for Florida Pecan Orchards 17

weight for C. spectabilis with Plots 2 and 1 second and third.
The average annual amount of green material returned to the
soil was relatively high for C. spectabilis and either Austrian
peas or hairy vetch in Plots 1 and 2, but for C. spectabilis and
oats in Plot 4 it was rather light, due to the sparse growth of
the oats.


Fig. 8.-Nodules on the roots of hairy vetch (left) and Austrian peas.

Average analyses of these crops shown in Table 2 do not
represent samples from this experiment, but are compiled from
data for like materials accumulated over a period of years by
the Department of Chemistry and Soils of this Station. These
show that in each ton of oven-dry material there were about
43 pounds of nitrogen in Austrian peas, 62 pounds in hairy vetch
and 29 pounds in Crotalaria spectabilis. Thus most nitrogen
was returned to the soils by hairy vetch and crotalaria in Plot 2,
second by Austrian peas and crotalaria in Plot 1 and third by
one crop of hairy vetch grown the first year of the experiment
and the C. spectabilis in Plot 4 (Fig. 8).






TABLE 3.-EFFECTS OF COVER CROPS AND FERTILIZERS ON THE GROWTH OF PECAN TREES.


Variety and
Plot* No.



Frotscher**
1- A*** ......................


2- A -.........................
B -.....- .. ........ ..

3- A ............................
B ............................
4- A ............................

B ............................

Stuart**
1- A*** ......................
B*** .....................

2- A ..... ............
B ...........................

3- A ............................
B ............................

4- A ...........................
B ............................


Growth increment per tree, area of trunk cross section in square inches


1928




10.2
12.1

8.5
10.6

8.0
3.5

10.2
5.8


8.7
10.4

7.8
11.1

7.1
8.9

7.9
9.7


I I Average Annual


1929




10.5
6.7

9.8
11.0

8.5
6.0

7.7
5.0


7.8
9.1

4.1
5.9

2.9
3.6

4.5
6.0


1930




5.2
11.5

6.1
11.4

4.6
5.3

1.6
7.9


6.4
11.2

6.9
5.6

3.3
3.5

4.4
5.5


1931




2.1
2.6

2.1
3.7

1.9
2.2

5.2
3.5


3.0
2.3

1.6
2.6

1.2
4.6

1.7


6.6I I .


1932 1933




11.4 4.6
12.3 5.0

10.4 3.1
12.6 3.1

8.3 1.4
9.2 2.5

6.8 2.0
7.9 3.5


See Table 2 for cover crops grown in each plot.
** Trees set 1904 on Norfolk fine sandy loam soil, experiment started 1927.
*** Fertilizers: A-All plots; superphosphate and sulfate of potash.
B-All plots sulfate of ammonia, superphosphate and sulfate of potash.


1928- 1928-
1934 1931



S7.4 7.0
8.6 8.2

7.3 6.6
9.2 9.2

5.2 5.7
5.5 4.2

5.6 6.2
6.5 5.5


Total




52.2
60.6

51.2
64.4

36.3
38.7

39.4
45.3


46.5
63.9

43.3
49.8

25.1
36.0

33.8
42.8


1932-
1934



8.1
9.2

8.2
9.2

4.4
7.2

4.9
7.7


6.8
10.3

7.6
8.2

3.5
5.1

5.1
6.6


Increase 1932-34
over 1928-31

Sq. in. | Percent


1.1 15.7
1.0 12.1

1.6 24.2
0 0

-1.3 -22.8
3.0 71.4

-1.3 -20.9
2.2 40.0


, v... ...


v.


, ... ,


, .. ,






A Cover Crop Program for Florida Pecan Orchards 19

EFFECTS OF COVER CROPS ON GROWTH AND YIELD
OF PECAN TREES
Growth increments were obtained by annually measuring
trunk circumferences at definite heights, calculating the area
of the cross-section for each tree, and averaging for each of
the different soil treatments. The trees were large and it was
impossible to make a sufficient number of accurate measurements
to show the actual twig growth. The average annual and total
growth increments in square inches per tree of the trunk cross-
section are shown in Table 3.
The data on growth were grouped into two periods to show
progressive effects of the treatments, the first period including
records for 1928-1931, and the second for 1932-1934. Total in-
crements for all years from 1928-1934 are shown also, as well
as annual averages.
Average annual growth increment was greater for 1932-1934
than for 1928-1931, except in a few instances (Table 3), and
all exceptions but one occurred where either no cover crops were
planted or where oats were grown during the winter. This
indicated that there was improvement in the soil condition as
a result of continuous cover crops of legumes in both winter
and summer.



















Fig. 9.-Crotalaria spectabilis in Stuart Plot 2 in which hairy vetch was
grown during the winter. Note the dense foliage on the trees and compare
with Plots 3 and 4 as shown in Figs. 10, 11 and 12.






Florida Agricultural Experiment Station


Neither non-legumes in winter with a legume in summer nor
the absence of planted cover crops gave satisfactory results in
trunk growth. However, there was some increase during the
second period over the first in both of these areas where sulfate
of ammonia was applied except that there was no difference in
the Stuart growth where no cover crop was planted.
It will be noted (Table 3) that Crotalaria spectabilis in sum-
mer with either Austrian peas or hairy vetch in winter produced
the greatest increase in tree growth. Differences in growth
response of the two varieties were only slight, however, and
Stuart trees showed up better in growth than they did in yields
(Fig. 9).
It will be noted in Table 3 also that growth increment after
1931 was greatest in each instance where sulfate of ammonia
was applied. The most wood growth during the period of the
experiment, however, was made by trees where the cover crops
consisted of legumes during both winter and summer and the
nitrogenous fertilizers were applied annually. (Figs. 10, 11,
12, 13, 14.)
Yields: The yield records as presented in Table 4 were grouped
into periods including the same years as given for growth. The
trend of tree yields followed rather closely growth response




















Fig. 10.-Stuart trees in unplanted Plot 3-A where no sulfate of am-
monia was applied. Note Crotalaria spectabilis in Plot 4, right background.
Note poor condition of trees and lack of foliage; compare with Plot 2 as
shown in Fig. 9.







A Corer Crop Program for Florida Pecan Orchards


Fig. 11.-Stuart trees in unplanted Plot 3-B where sulfate of ammonia
was applied. Has somewhat better foliage than in Plot 3-A as shown in
Fig. 10. Note Crotalaria spectabilis in Plot 4, right background.


Fig. 12.-Crotalaria spectabilis in Stuart Plot 4 in which oats were
grown each winter. Note the sparse foliage on the trees and compare with
Plot 2 as shown in Fig. 9.






Florida Agricultural Experiment Station


Fig. 13.-Stuart buffer row (right) adjacent to hairy vetch Plot 2-B, left,
and unplanted Plot 3-B. Complete fertilizers applied.


Fig. 14.-Frotscher unplanted Plot 3-B (left) and buffer row adjacent to
hairy vetch Plot 2-B. Complete fertilizer applied.






A Cover Crop Program for Florida Pecan Orchards


in the different treatments. The average annual yields per
tree are shown for the different plots, and were calculated to
an acre basis of 17 trees. They are pictured graphically in Fig.
15 to show more clearly the effects of the cover crops and the
fertilizers.
Production of each variety during 1928-1931 did not vary
greatly with different soil treatments. There was a slight ad-
vantage in the legume plots but it was not significant, since the
differences were almost the same as those shown for the first
record in 1928.
By examining the data presented in Table 4 it will be noted
that nut production under all treatments averaged relatively
low for both varieties during the first period of 1928 to 1931.
For the second period of 1932 to 1934, however, the average yield
of Frotscher amounted to 35.3 and 34 pounds per tree without
sulfate of ammonia where Austrian peas and hairy vetch were
grown, but with sulfate of ammonia trees on soils growing the
same cover crops produced 56.9 and 57.1. Therefore in the two
all-legume plots the increase for the second period over the first
amounted to over 400 pounds per acre with superphosphate
and sulfate of potash only, and more than 750 pounds where
nitrogen, phosphoric acid and potash all were applied. These
increases were rather significant and clearly show the value of
maintaining soil fertility with the use of legumes in both winter
and summer, since yields were decidedly higher with leguminous
cover crops than in the other plots.
The data in Table 4 show that Stuart, though lower in pro-
duction, followed the same general trends as the Frotscher.
Tree yields consistently increased during the second period over
the first where the winter legumes and crotalaria were grown
in comparably fertilized sections.
There were only slight differences in production of trees
under various treatments during the first period. However,
it can be observed in Table 4 that during the second period the
trees growing where winter and summer legumes were returned
to the soil produced consistently heavier than where no cover
crops were planted. The combination of oats in winter and
Crotalaria spectabilis in summer as green manure crops returned
to the land failed to give satisfactory results, and except in one
instance trees in this plot produced fewer nuts than where only
native vegetation was returned to the soil.











Fig. 15.-Average annual yield of pecans as affected by
cover crops and fertilizers.
1-A. Austrian peas and C. spectabilis with superphosphate and
sulfate of potash.
ST? A ------


LJ



z


000-


0oo0


S-J. us r an peas aund I. spectabuilis withl sulfae of ammonia,
superphosphate and sulfate of potash.
2-A. Hairy vetch and C. spectabilis with same fertilizer as 1-A.
800oo 2-B. Hairy vetch and C. spectabilis with same fertilizer as 1-B.
3-A. Natural growth only with same fertilizer as 1-A.
3-B. Natural growth only with same fertilizer as 1-B.
700 4-A. Oats and C. spectabilis with same fertilizer as 1-A.
4-B. Oats and C. spectabilis with same fertilizer as 1-B.

600o


500-


400- FROTSCHER STUART d"


300- -


200 I c






I-A 1-B Z-A 2-B 3-A 3-B 4-A 4-B- Plots-.-A 1-B 2-A 2-B 3-A 3-B 4-A 4-8











TABLE 4.-EFFECTS OF COVER CROPS AND FERTILIZER ON THE YIELD OF PECAN TREES.


Variety and
Plot No.*


Frotscher**
1-A*** ...........

2--A ...........
B .................

3-A ..................
B ..................

4-A ..................
B .................

Stuart**
1-A*** ............
B*** ............

2-A ...............
B ..................

3-A .................
B ..................

4-A ..................
B .................


YIELD PER TREE IN POUNDS


19311 1932


1933



18.5
29.6

36.7
58.0

20.6
16.6

15.5
1.7

24.1
32.4

23.6
40.0

7.6
12.5

16.4
10.9


1934 Total



62.0 142.1
L15.0 221.4

42.7 133.0
83.6 206.2

16.0 63.9
30.3 88.8

5.2 49.2
18.0 57.9


74.6
95.8

74.0
89.5

35.0
50.3

49.6
44.9


Average Annual
1928-1934 1 1928-1931


Per
Acret


845.1
537.2

323.0
501.5

154.7
215.9

119.0
141.1

180.2
232.9

178.5
217.6

85.0
122.4

120.7
108.8


Per I Per
Tree I Acret


Per
Tree


20.3
31.6

19.0
29.5

9.1
12.7

7.0
8.3

10.6
13.7

10.5
12.8

5.0
7.2

7.1
6.4


See Table 2 for cover crops grown in each plot.
** Trees set 1904 on Norfolk fine sandy loam soil. Experiment started in 1927.
*** Fertilizers: A, all plots, superphosphate and sulfate of potash only.
B, all plots, sulfate of ammonia, superphosphate and sulfate of potash.
t Calculated on basis of 17 trees per acre.


Average Annual Increase
of 1932-1934 over
1928-1931
1932-1934 Pounds I
Per Per Per Per | Percent
Tree Acret Tree Acref I _


35.3 600.1 26.3 447.1 292.2
56.9 967.3 44.3 753.1 351.5

34.0 578.0 26.2 445.4 335.8
57.1 970.7 48.4 822.8 556.8

13.0 221.0 6.9 117.3 111.2
17.5 297.5 8.4 142.8 92.3

8.2 139.4 2.1 35.7 34.4
9.9 168.3 2.9 49.3 41.4

15.2 258.4 8.0 136.0 111.1
22.2 377.4 14.9 253.3 204.1

14.1 239.7 6.2 105.4 78.4
20.2 343.4 13.0 221.0 180.5
4.6 78.2 -0.7 -11.9 -13.2
10.1 171.7 5.1 86.7 102.0

8.5 144.5 2.5 42.5 41.6
6.8 115.6 0.7 11.9 11.4


I I I I I I I


I I I I I I






Florida Agricultural Experiment Station


Where all cover crops consisted of legumes the yield increase
of Frotscher trees amounted to more than 660 and 350 pounds
per acre with and without sulfate of ammonia, respectively,
over that in the unplanted plot. Where oats and C. spectabilis
were grown in Plot 4 the nut production was less than where
no cover crops were planted.
The Stuart trees produced 100 to 200 percent more nuts with
winter and summer legumes than without cover crops. How-
ever, it will be noted in Table 4 that owing to light yields the
increase amounted to only 171 to 205 pounds per acre during
the second period. As with Frotscher, where oats in winter
and C. spectabilis in summer were grown and returned to the
soil, Stuart yields were much lighter than in the all-legume plots.
The production of nuts after 1931 was materially increased
where sulfate of ammonia was applied, except in one instance.
For the period 1932 to 1934 the greatest increase in yield was
made by the Frotscher trees where both winter and summer
legumes were returned to the soil. The additional production
amounted to 367.2 and 392.7 pounds per acre, respectively,
where Austrian peas and hairy vetch were grown and sulfate
of ammonia was applied.
Table 4 shows further that there was practically no difference
during 1932 to 1934 in yields of the trees in each of the two
legume plots when comparing areas fertilized alike. Frotscher
produced heavier crops than the Stuart, however, but the trees
of both varieties in the legume plots responded better to the
additional ammonia applications than where either no planted
cover crops or where oats and C. spectabilis were grown.

NUT SIZES AND KERNEL PERCENTAGES
According to Blackmon and Ruprecht (3), fertilizers have
very little effect on size and kernel content of pecan nuts. Moist-
ure proved to be an important factor, and without an adequate
supply it was impossible for the best of varieties to produce
fully developed and well filled nuts, especially when the trees
were carrying heavy crops.
Data on nut sizes and kernel percentages are given in Table
5 for the same grouping of years as for growth and yield; similar
data are presented in detail for the 1934 crop in Table 6. It
will be noted that sizes and kernel percentages for the first
group are identical for both sections of any one plot. This was
because yield samples were not separated until the second year
after summer applications of sulfate of ammonia were begun.






A Cover Crop Program for Florida Pecan Orchards 27

Representative samples of nuts were collected from each tree
in the experiment at harvest, measured by hand and the per-
centage of kernel determined.
Frotscher:-During the first period the nuts produced by the
trees in legume Plots 1 and 2 ran 70 percent or more to the
larger sizes, while from the check and oat Plots 3 and 4 only
39 percent were in this group. However, there were practically
no differences in the percentage of kernel in the samples from
the different plots. In the second period without a planted
cover crop and where oats and Crotalaria spectabilis were grown
in winter and summer, respectively, the trees produced a higher
percentage of 15/16 inch and larger nuts than where the legumes
were grown. However, because of a heavy yield there was a
greater quantity of nuts in the larger grades in the legume than
in the non-legume and check plots. Again, the percentage of
kernel did not vary to any great extent but ran slightly higher
than during the first period.
In Table 6 details are given for the 1934 crop. An examina-
tion of the data shows that trees in the legume plots produced
a lower percentage of nuts sizing 15/16 inch and larger than
those in the winter non-legume and check plots. However,
since yields from the legume plots were much heavier, there
were more nuts in the larger sizes from these plots. The per-
centage of kernel varied very little in the different plots, but
it was somewhat higher than during 1928-1931.
The average .size for 1928-1934 showed somewhat higher per-
centages of larger nuts from the trees where the legumes were
grown than for the other treatments. This was because of high
percentages of larger nuts obtained during the first period when
the yields were much lighter. Moisture conditions were not so
favorable during this time and the mulch produced by the winter
cover crops seems to have been more effective. It will be noted
also that kernel percentages were about the same when averaged
over the entire period for the different plots.
Stuart:-During 1928 to 1934 more than half of the nuts in
all plots were 14/16 inch and smaller. The percent kernel did
not vary greatly when averaged, although it was somewhat less
for the nuts produced in legume Plot 2-A to which no sulfate
of ammonia was applied.
In 1934 the trees in legume Plot 2-B, which received additional
ammonia, produced the highest percentage of 15/16 inch nuts
and larger. Nut sizes varied somewhat in all plots but did not














TABLE 5.-EFFECTS OF COVER CROPS AND SULFATE OF AMMONIA ON SIZE AND KERNEL PERCENTAGE OF PECAN NUTS.


Variety and
Plot No.*



Frotscher**
1-A***.....


Bess-
B*** ......................

2-A ..................... ..
B .................... .......

3-A .........................
B ........................

4-A .............. ..
B ............ ..... .......

Stuart**
-A***......
B*** ............. ......

2-A .................._ ...
B ..........................

3-A ................._
B .........-.................

4-A .......... ........
B ......... ..... ....


1928-1931 t
Nut diameters, 16th of an inch.
Percent of nuts in each
size class.

16 and 13 and
larger 15 14 smaller


0 70.0 26.7 3.3
0 70.0 26.7 3.3

0 75.0 21.7 3.3
0 75.0 21.7 3.3

0 31.7 61.7 6.6
0 31.7 61.7 6.6

0 28.3 71.7 0
0 28.3 71.7 0

0 22.5 72.5 5.0
0 22.5 72.5 5.0

0 32.5 67.5 0
0 32.5 67.5 0

0 12.6 87.5 0
0 12.5 87.5 0

0 22.6 77.5 0
0 22.6 77.5 0


Percent
kernel
in
total
sample


46.8
46.8

47.5
47.5

47.9
47.9

47.3
47.3

49.8
49.8

48.7
48.7

50.1
50.1

46.7
46.7


1932-1934
Nut diameters, 16th of an inch.
Percent of nuts in each Percent
size class, kernel
in
16 and 13 and total
larger 15 [ 14 smaller sample


3.0 31.6 46.1 19.3 50.4
1.6 29.4 56.0 13.0 49.8

2.9 36.1 45.4 15.6 50.5
3.9 29.9 51.5 14.7 50.5

5.0 42.5 43.6 8.9 50.1
12.7 50.2 31.7 5.4 50.9

10.0 46.9 32.6 10.5 50.7
7.4 39.1 42.4 11.1 50.3


1.8
0

0
8.4

0
0

0
0


33.9
19.6

25.1
29.2

34.7
25.1

15.9
29.1


46.6
62.7

54.8
44.2

43.2
46.7

51.5
46.4


17.7
17.7

20.1
18.2

22.1
28.2

32.6
24.5


45.6
47.1

43.6
48.8

49.1
46.8

47.9
49.4


1928-1934
Nut diameters, 16th of an inch.
Percent of nuts in each
size class.

16 and I 13 and
larger 15 I 14 smaller


1.5 50.8 36.4 11.3
0.8 49.7 41.3 8.2

1.4 55.5 33.5 9.6
2.0 52.4 36.6 9.0

2.5 37.2 52.5 7.8
6.3 40.9 46.7 6.1

4.0 35.8 56.0 4.2
3.7 33.8 57.0 5.5


0.9
0

0
4.2

0
0

0
0


29.3
20.7

28.0
30.9

23.8
18.8

19.2
25.8


57.2
66.0

59.9
65.9

65.2
67.1

64.5
61.9


12.6
13.3

12.1
9.0

11.0
14.1

16.3
12.2


Percent
kernel
in
total
sample


48.6
48.3

48.9
49.0

49.0
49.4

48.6
48.7

47.3
48.2

45.6
48.8

49.6
48.5

47.3
48.1


See Table 2 for cover crops grown in each plot.
** Trees set 1904 on Norfolk fine sandy loam soil, experiment started in 1927.
*** Fertilizers: A, all plots ; superphosphate and sulfate of potash only.
B, all plots; sulfate of ammonia, superphosphate and sulphate of potash.
SThe sulfate of ammonia applications were started in 1930, therefore, the samples of nuts for A and B in each plot were not separated until 1932.







A Cover Crop Program for Florida Pecan Orchards 29

TABLE 6.-EFFECTS OF COVER CROPS AND SULFATE OF AMMONIA ON SIZE
AND KERNEL PERCENTAGE OF PECAN NUTS PRODUCED IN 1934.


Fertilized with superphos- Fertilized with sulfate of
Nut phate and sulfate of potash ammonia, superphosphate
Diameters only (A) and sulfate of potash (B)
16th of an in. Percent of crop in Percent Percent of crop in Percent
each size class kernel each size class kernel


FROTSCHER
Plot 1
16 and larger 8.9 49.9 4.9 49.3
15 40.0 48.5 43.2 50.6
14 39.6 50.7 41.0 51.4
13 and smaller 11.5 50.9 10.9 49.9
Plot 2
16 and larger 8.7 50.1 11.7 50.6
15 36.1 50.1 40.7 51.6
14 43.2 49.8 36.5 50.5
13 and smaller 12.0 51.2 11.1 50.7
Plot 3
16 and larger 14.9 49.6 38.5 51.6
15 42.5 50.6 37.6 48.8
14 36.2 50.6 23.0 51.6
13 and smaller 6.4 49.4 0.9 49.5
Plot 4
16 and larger 20.0 50.0 22.3 50.7
15 50.9 49.9 47.1 51.9
14 29.1 50.9 27.3 51.6
13 and smaller 0 ...... 3.3 53.2

STUART
Plot 1
16 and larger 4.6 42.6 0
15 44.9 46.4 23.6 47.9
14 46.7 46.9 59.0 47.0
13 and smaller 3.8 42.9 17.4 46.3
Plot 2
16 and larger 0 ...... 16.8 46.4
15 26.9 43.7 56.5 45.4
14 55.2 47.8 20.5 41.0
13 and smaller 17.9 47.9 6.2 42.0
Plot 3
16 and larger .... 0 ......
15 69.4 47.7 46.9 46.2
14 24.5 48.6 35.1 45.6
13 and smaller 6.1 46.9 18.0 43.1
Plot 4
16 and larger 0 ...... 0
15 31.9 44.4 52.6 46.1
14 54.9 47.0 32.4 47.9
13 and smaller 13.2 47.6 15.0 43.4






Florida Agricultural Experiment Station


follow any definite trend that could be correlated with the treat-
ments. Kernel percentages did not vary greatly, and were low
for several sizes of nuts.
Therefore, an examination of the data in Table 5 will show
that there were no consistent differences in sizes of Frotscher
and Stuart nuts produced under different treatments during the
two periods of the experiment, although there were some varia-
tions.
By referring to Table 5 it will be noted further that the
greatest variation occurred with the Frotscher during 1928-
1931 when there were light nut yields in all years except 1928.
During this period the percentage of nuts sizing 15/16 inch
were much higher in Plots 1 and 2 in which legumes were grown
during winter and summer. This was due no doubt to a more
favorable moisture condition in the soil maintained by the mulch
produced by the winter legumes. The kernels on a percentage
basis did not vary consistently when examined collectively, and
the quality was characteristic of the two varieties.

EFFECTS OF COVER CROPS ON ORCHARD RETURNS

In Table 7 and in Fig. 16 average annual returns are shown
for the different plots covering the first and second periods,
as well as for all years that the experiment was conducted. The
price of fertilizers and seed was based on cost of these materials
from 1927 to 1934 and averaged. Cultivation was the same
in all plots and, therefore, it was not charged for as it was not
materially changed from that practiced by the grower prior
to the time the experiment was initiated. The value of each
crop was calculated from prices at which the nuts were sold
by the grower, and averages are shown for the two periods
separately.
The average annual cost of materials to produce each pound
of nuts was higher during 1928 to 1931 than 1932 to 1934, ex-
cept with the Stuart in two instances. It will be noted in Table
7 that legumes in winter and summer produced Frotscher nuts
at the lowest cost for fertilizer and cover crop seed during 1932
to 1934. The Stuart, however, with the same cover crops cost
more per pound of nuts because of the lower production. Table
7 also shows that the nuts which cost the most during 1932 to
1934 were produced by the Stuart where oats and Crotalaria
spectabilis, respectively, were grown during the winter and
summer and sulfate of ammonia was applied annually.







Fig. 16.-Average annual returns for the pecans after de-
ducting cost of fertilizer and seed.
1-A. Austrian peas and C. spectabilis with superphosphate and
sulfate of potash.
1-B. Austrian peas and C. spectabilis with sulfate of ammonia,
superphosphate and sulfate of potash.
2-A. Hairy vetch and C. spectabilis with same fertilizer as 1-A.
2-B. Hairy vetch and C. spectabilis with same fertilizer as 1-B.
3-A. Natural growth only with same fertilizer as 1-A.
3-B. Natural growth only with same fertilizer as 1-B.
4-A. Oats and C. spectabilis with same fertilizer as 1-A.
4-B. Oats and C. spectabilis with same fertilizer as 1-B.




STUART





I I Ir nI


FROTSCHER







Florida Agricultural Experiment Station


Returns per acre of the Frotscher above materials cost were
relatively low during each of the first four years. However, for
1932 to 1934 they were $122.40 and $126.65 with Austrian peas
and hairy vetch, respectively, which received sulfate of ammonia,
and $76.84 and $72.59 with the same crops, respectively, where
no sulfate of ammonia was applied. The data in Table 7 show
that returns were lower where oats were grown than with no
planted cover crop, except in one section. Therefore, even with
the low prices received for the nuts during 1932 to 1934 the
returns above cost of materials in the legume plots were quite
significant and showed a favorable increase. For the duration
of the experiment the returns were highest where sulfate of
ammonia was applied and legumes were grown in both winter
and summer. Likewise, without cover crops and in the plot
where oats and C. spectabilis were grown, returns were slightly
higher where sulfate of ammonia was applied.
Stuart produced fewer nuts than Frotscher and therefore gave
much lower returns; consequently each pound of nuts carried
a higher cost for materials which was lower in the legume than
in the other plots for 1932 to 1934. Returns above cost for
materials figured on an acre basis of 17 trees, however, showed
that during the second period they were $28.56 and $26.01 where
no sulfate of ammonia was applied in the legume Plots 1 and 2,
respectively, but where sulfate of ammonia was applied they
were $40.12 and $33.49. The returns were slightly higher also
in the same two plots where sulfate of ammonia applications
were made for the duration of the experiment. With complete
fertilizer applications during 1932 to 1934 with sulfate of am-
monia, trees in the unplanted plot gave a greater return than
in the section where only phosphorus and potash were applied.
It will be seen in Table 7 that even with the light yields and
low nut prices which prevailed the returns of the Stuart above
cost of materials were much better with legumes than they were
in the unplanted and winter non-legume Plots 3 and 4.

EFFECTS OF COVER CROPS ON THE SOIL
TUBE SAMPLES
In 1928 and again in 1933 soil samples were taken at three
depths from definite locations between the trees in sections A
of each plot to which no sulfate of ammonia was applied. The
soil from each plot for the given depths of 0-9 inches, 9-21 inches,
and 21-33 inches was mixed into a composite sample, passed
through a two millimeter sieve, and the percent organic matter











TABLE 7.-AVERAGE ANNUAL RETURNS IN THE PECAN COVER CROP EXPERIMENT.


Variety and Plotst


Frotscher*
1- -A ..........................
S........................

2-A ........................
B ................ .......


3 A .........................
B ........ ..........

4 -A ............................
B ...........................

Stuart*
1 At ..................
B$ ...................

2- A ..... ......................

3- .................... ......
3- A ............................
4- B ............................
B ......................
B A .. -


Average Annual Fertilizer and Seed
Cost per Pound of Nuts
Produced***
1928-1931 I 1932-1934 I 1928-1934


$ .039 $ .010 $ .017
.039 .011 .017

.045 .011 .019


.057

.036
.040

.057
.071


.011

.017
.030

.043
.066


.019

.024
.034

.050
.067


I Average Annual Returns A


1928-1931


Per Tree


$1.81
2.58

1.50
1.54

1.35
1.86

1.06
1.15

1.17
1.04

1.36
1.05

0.98
0.77

0.94
0.82


1 1932


Per Acre** Per Tree


$30.77
43.86

25.50
26.18

22.95
31.62

18.02
19.55


19.89
17.68

23.12
17.85

16.66
13.09

15.98
13.94


above Cost of Materials.***
-1934 1928-1934

I Per Acre** Per Tree I Per Acre**


$76.84
122.40

72.59
126.65

26.01
31.62

12.58
12.24


28.56
40.12

26.01
33.49

6.63
14.28

13.26
4.42


$50.15
75.31

45.73
69.19

23.97
31.45

15.64
16.66


23.46
27.20

24.14
26.52

12.41
13.60

14.79
9.86


Trees set 1904 on Norfolk fine sandy loam soil.
** Calculated on basis of 17 trees per acre.
*** Average annual fertilizer cost per tree: superphosphate and sulfate of potash, 22c; sulfate of ammonia, superphosphate and sulfate of potash,
52c; and the seed cost per tree in Plots 1, 2, and 4, 13c.
**** The average annual returns as shown are after deducting fertilizer and seed cost. The nuts were sold, orchard run, at the following prices per
pound: 1928, 26c; 1930, 23c; 1931, 14c; 1932, 14c; 1933, 13c; and 1934, 14c.
t See Table 2 for cover crops grown in each plot.
I Fertilizers: A-All plots = superphosphate and sulphate of potash only.
B-All plots = sulfate of ammonia, superphosphate and sulfate of potash.


1932







Florida Agricultural Experiment Station


and total nitrogen and the pH of each were determined. Data
obtained from the soil analyses are presented in Table 8.
Soil Reaction:-The soil samples at all depths and from all
plots in 1928 and 1933 were acid in reaction. The acidity of
the surface 0-9 inches decreased during the period over which
the experiment was conducted. This decrease was greatest where
no planted cover crops were grown, and least where the summer
legume and the winter non-legume were returned to the soil.
Nitrogen:-Available nitrogen in the soil is important in plant
growth, and orchard practices that will maintain it will produce
best results with pecans. Analyses do not necessarily show
what a certain soil may require; but they can be employed to
show changes that may take place over a definite period, and
they were so used here in determining the nitrogen content of
the soil at the beginning of the experiment and six years later.
It was not intended that they show the percent of available
nitrogen in the soil for the two sampling dates, but rather that
they show the totals only.
Data in Table 8 show that from 1928 to 1933 the nitrogen
content of the surface soil increased where planted cover crops
were grown and decreased in the unplanted plot. At the lower
depths there was practically no change in the nitrogen content.
Samples of surface soil taken in 1928 and 1933 from the winter
legume Plots 1 and 2 contained 14.28 and 16.32 percent more
nitrogen at the latter date. This was slightly less than the
increase where the winter non-legume was grown. The nitrogen
content of the 0-9 inch soil samples, although differing slightly,
was consistently higher in 1933 than in 1928 in all planted plots,
and likewise lower in the unplanted plot. This indicated rather
positively that nitrogen can be maintained and even increased
in the surface soil with the proper use of suitable cover crops
in winter and summer.
This is in agreement with the findings of Fowler and Lewis
in Georgia (6). They reported increases of total nitrogen in
the surface of Norfolk sandy loam soil where winter legumes
consisting of either Austrian peas or Monantha vetch were
grown.
For the period of the experiment, data in Table 2 show that
the most nitrogen per acre was returned to the soil by hairy
vetch and Crotalaria spectabilis in Plot 2 and amounted to a
total of 603.4 pounds; Austrian peas and C. spectabilis in Plot 1
were second, returning 414.7 pounds. In Plot 4 in which one
crop of vetch was grown at the beginning of the experiment











TABLE 8.-EFFECTS OF COVER CROPS ON


Plot**


1


2


3


4


Soil
Depth
Inches

0-9
9-21
21-33

0-9
9-21
21-33

0-9
9-21
21-33

0-9
9-21
21-33


1928
pH

6.13
6.03
5.93

6.20
5.80
5.86

6.13
5.66
5.80

6.12
6.03
6.03


1933
pH

6.32
6.18
5.86

6.35
6.18
5.85

6.40
5.86
5.90

6.26
6.01
5.83


THE NITROGEN AND ORGANIC MATTER CONTENT AND THE PH OF THE
PECAN EXPERIMENT*.


TOTAL NIRTOGEN
March September Gain or
1928 1933 Loss
Percent Percent Percent

0.042 0.048 +14.28
0.028 0.027 3.57
0.032 0.029 9.34

0.049 0.057 +16.32
0.029 0.029 0
0.032 0.031 3.12

0.046 0.044 4.34
0.034 0.032 5.88
0.031 0.028 9.67

0.048 0.059 +22.11
0.033 0.033 0
0.028 0.024 -14.28


March
1928
Percent

2.27
2.48

2.77
1.93
3.81

2.48
2.92
5.33

2.97
2.68
3.28


ORGANIC MATTER"


September
1933
Percent

2.34
1.87

2.51
1.87
3.69

2.30
3.14
4.98

3.13
2.99
3.50


SOIL IN THE


Gain or
Loss
Percent

+ 3.08
-24.59

9.38
3.10
3.14

7.41
+ 7.53
S6.56

+ 5.38
+11.57
+ 6.70



-


All determinations were made for that part of the
*" See Table 2 for cover crops grown in each plot.
*** Determined by the loss on ignition.


soil which passed through a two millimeter sieve.


1___________







Florida Agricultural Experiment Station


and oats and C. spectabilis in winter and summer respectively,
annually thereafter, the total nitrogen returned by the two
legumes amounted to 237.0 pounds per acre.
The nitrogen in the soil of Plot 4, in which the cover crops
consisted of a winter non-legume and a summer legume, although
highest of all for the 0-9 inch depth, evidently was not in an
available form during the maximum growing season and could
not be utilized. Growth and yield of trees were significantly
greater in Plots 1 and 2 in which legumes were grown annually
in winter and summer. However, it should be pointed out that
hairy vetch was grown on Plot 4 the first year and produced
13,400 pounds of green material per acre and that the crotalaria
was heaviest in this plot each year except 1928 and 1931. The
nitrogen returned was no doubt fixed in the soil by the oats,
and it was thus unavailable to the trees and probably accounted
for the poor results in Plot 4.
TABLE 9.-EFFECTS OF COVER CROPS ON THE BASIC FERTILITY OF THE SOIL
AS DETERMINED WITH SUDAN GRASS GROWN IN VOLUME SAMPLES TAKEN
IN THE PECAN EXPERIMENT IN 1934*.
Organic Dry Weight
I Nitrogen Matter of Sudan Nitrogen in Sudan Grass
Plot** in Soil in Soil Grass Sudan
Avg. percent Avg. percent Avg. grams IAvg. percent Avg. grams
1 0.049 2.34 11.6 0.54 0.063
2 0.059 2.68 14.8 0.51 0.075
3 0.047 2.48 8.1 0.56 0.045
4 0.055 2.78 11.0 0.63 0.069

These were taken with a volume sampler which gave a cube of surface
soil 6x6x6 inches. The soil was passed through a two millimeter sieve
before determinations were made and the Sudan grass planted.
** See Table 2 for cover crops grown in each plot.

Organic Matter:-By referring to Table 8 it will be seen that
the organic matter content of the surface soil, as determined
by loss on ignition, was higher in 1933 than in 1928 in all planted
plots except 2, and that it was lower in the unplanted Plot 3.
The greatest increase in organic matter occurred in the 0-90
inch soil sample from Plot 4 where the most Crotalaria spec-
tabilis was grown and returned. It should be pointed out that
the rough organic materials in pecan soils are important, en-
couraging bacterial activity while decaying and also helping
somewhat in moisture conservation. Well decomposed organic
material after it becomes thoroughly incorporated as an integral







A Cover Crop Program for Florida Pecan Orchards 37

part of the soil is called humus, and is different from the rough
organic material. In these samples the humus content was
determined.
VOLUME SOIL SAMPLES
In 1934 volume samples were taken from the same location
as those of different depths in A of each plot with a volume
sampler which took out a cube of surface soil 6 x 6 x 6 inches,
each having an average weight of about 10 pounds. The soil
was passed through a two millimeter sieve and the nitrogen
determined; it was then placed in jars and nine plants of Sudan
grass were grown in each so as to determine its relative pro-
ductive ability following the different treatments. The data
obtained from these samples are presented in Table 9.
Nitrogen:-The nitrogen content of the volume soil samples
averaged 0.049, 0.059, 0.047, and 0.055 percent, respectively, for
Plots 1, 2, 3, and 4. It was highest, therefore, in Plot 2 in which
hairy vetch and Crotalaria spectabilis were grown, second in
the winter non-legume and summer legume plot, third with
Austrian peas and C. spectabilis, and lowest where no planted
crops were grown. Nitrogen in the volume samples was slightly
higher than it was in the 0-9 inch depth taken in 1933, for all
plots except the winter non-legume in which it was slightly
lower. However, it followed the same general trend as in 1933
and was in practical agreement with the 0-9 inch tube samples,
the differences not being significant.
Organic Matter:-The organic material as determined by loss
on ignition in the volume samples did not vary materially from
those of the 0-9 inch depth for 1933 as shown in Table 8, except
that it was slightly higher in Plots 2 and 3 and lower in 4.
Therefore, the organic content in the volume soil samples fol-
lowed rather closely the general trend of the 0-9 inch tube
samples.
Sudan Grass Growth:-Growth made by the Sudan grass was
heaviest in soils from the legume plots and lightest from the
unplanted plot. Soil from the oats plot grew plants almost as
heavy as those from the soil of the Austrian peas plot. (See
Table 9.) While there was only a slight difference in the weight
of the Sudan grass growth in favor of the Austrian peas over
the oats, apparently there were significant differences in favor
of the cover crops over the unplanted soil. This indicated that
soil in the planted plots was more fertile than in the unplanted
check, and that soil from Plot 4 where oats were grown during







Florida Agricultural Experiment Station


the winter had a greater ability to produce Sudan grass than:
that from Plot 3 where no cover crop had been planted. The
pecan yields of both varieties as shown in Table 4 were in
rather close agreement with these results, except with Frotscher
in two instances, one with no cover crops and the other where
oats and C. spectabilis were grown.
However, the amount of nitrogen recovered in the Sudan grass,
as will be noted in Table 9, followed fairly closely percentages.
in soils from the various treatments. It is further shown that.
the quantity of nitrogen recovered in plants grown in soil from
the unplanted Plot 3 was lowest, while in hairy vetch Plot 2.
it was highest. As will be noted in Table 2, the greatest amount
of nitrogen was returned to the soil by hairy vetch and C. spec-
tabilis in Plot 2 and amounted to 603.4 pounds per acre.
The availability to the tree of the nitrogen taken up by the
non-leguminous cover crop of oats evidently is not of the same
order as the availability of the nitrogen to Sudan grass. How-
ever, it must be borne in mind that the spring season is a period
of maximum utilization of nitrogen by the pecan tree, and that
the nitrogen would not be available from oats during this period.
On the other hand, the Sudan grass studies were made after
a long period of decomposition, and the nitrogen effectively con-
served by the non-leguminous cover was available to some ex-
tent after a prolonged period of decomposition in the soil.

DISCUSSIONS AND RECOMMENDATIONS
The data presented definitely point to beneficial effects of
leguminous cover crops on growth and yield of Frotscher and
Stuart pecan trees on Norfolk fine sandy loam soil. While the-
trees responded to a greater degree where complete fertilizer
applications were made, there were no significant differences
until cover crops had been annually grown and returned to the
soil for four years. Therefore, growers should keep in mind
the fact that it requires several years to revive trees in poor
condition and obtain profitable nut production. Quantity pro-
duction is possible, therefore, with potentially heavy bearing
pecan varieties that would otherwise give light yields, by prac-
ticing a continuous program of annual cover-cropping and judi-
cious fertilization.
Hairy vetch and Crotalaria spectabilis produced the greatest
amount of green material which contained the most nitrogen
to be returned to the soil, followed closely by Austrian peas.






A Cover Crop Program for Florida Pecan Orchards


and C. spectabilis. Oats followed by C. spectabilis gave the least
tonnage of organic material, although C. spectabilis made a
heavier growth in this plot than in those where the winter
legumes were grown. Crotalaria spectabilis could not make
maximum growth in any plot due to the shading of the ground
by large trees.
The trees responded to leguminous cover crops and sulfate
of ammonia and gave significant increases in growth and yields.
Yields during the first four years were quite low, but for the
three years following they were higher by 292 to 556 percent
for Frotscher and 78 to 204 percent for Stuart. Frotscher
produced much heavier crops than Stuart and consequently gave
much greater returns above cost of materials.
The combination of oast in winter and C. spectabilis in summer
failed to increase nut production and gave unsatisfactory results.
In fact, nut production during 1932 to 1934 was better in each
section of the unplanted plot than where oats were grown,
except with the Stuart in one instance.
There were no significant differences in sizes and kernel per-
centages of nuts produced under conditions maintained in the
various plots. Therefore, growers may follow a program of
cover-cropping and fertilization, such as the one giving the
highest yield in the experiment, without fear of impairing the
size and quality of the nuts.
The nitrogen content of the surface soil in the experiment
increased where cover crops were grown and decreased with
a natural growth of native non-legumes. The organic content
of the surface soil during the period of the experiment showed
a decrease in the unplanted plot and in one plot where the cover
crops were grown, while the other two planted plots showed
slight increases. Sudan grass produced heaviest growth on soils
from hairy vetch Plot 2, second from Austrian peas Plot 1, third
from oat Plot 4, and lowest from the unplanted Plot 3. Pecan
yields where either Austrian peas or hairy vetch were grown
followed by C. spectabilis were in agreement with the Sudan
grass growth.
Results obtained in this experiment would indicate that a
profitable program to follow in bearing pecan orchards located
on suitable soils, such as the one worked with, would be to grow
winter and summer legumes. Such a program would consist
in the planting of hairy vetch, Austrian peas or some other
legume which would make comparable growth during winter,






Florida Agricultural Experiment Station


and of growing C. spectabilis during summer. Sometime during
April or May the winter crops should be returned to the soil
with a light disking, and during August the summer crop should
be mowed (Fig. 17).


Fig. 17.-Volunteer Crotalaria spectabilis in Jefferson County where
original test plot was planted in May 1925. Photographed in October 1927.

In handling summer cover crops several points should be kept
in mind. Rainfall in Florida is generally sufficient during June,
July, and August to permit plant growth without serious com-
petition with the trees for soil moisture. During dry summers,
however, the land should be disked lightly or the cover crop
mowed to prevent competition with the trees; but with adequate
moisture in the soil the cover crop can be allowed to grow until
August, when it should be mowed or the growth checked with
a shallow disking. Seed of winter legumes should be planted
during the last of October or in November if there is adequate
soil moisture, but satisfactory growth can be obtained with
plantings as late as December 20, provided conditions are favor-
able throughout the remainder of the winter and early spring.
Winter legumes planted in the experiment, as well as others
mentioned, have been observed making satisfactory growth in
all sections of northern Florida on soils capable of growing
pecans. However, the heavier types of soils will give best results







A Cover Crop Program for Florida Pecan Orchards 41

and produce heavier quantities of green manure to be returned.
The hairy vetch in Fig. 18 made a good growth on Coxville soil
in Bradford County, and a
mixture of hairy vetch and
Austrian peas growing on
Bladen fine sandy loam in
a Duval County orchard is
shown in Fig. 19. Figure 20 i
20 shows Austrian peas I
growing on Norfolk soil in
the pecan variety orchard
on the Experiment Station
Farm at Gainesville. With
proper handling, therefore,
these winter legumes can
be successfully grown on
lands suited to pecans
throughout northern and
western Florida.
The fertilizing program
could be one similar to that
practiced in this experiment
which would consist of 200 Fig. 18.-Hairy vetch growing on
to 300 pounds of 16% Coxville soils in a Bradford County
to 300 ipoaunds of 16 pecan orchard.
superphosphate and 50 to
60 pounds of sulfate of potash per acre applied broadcast to the
soil just before the winter cover crop seed are planted. Some
suitable form of ammonia such as sulfate of ammonia or nitrate
of soda can be applied during June and July at the rate of 5 to
20 pounds per tree, depending upon size, or about 1/1 to 1/ pound
for each inch of circumference of the tree trunk. However, if
summer cover crops only are being grown, either with or with-
out inter-crops, then it is recommended that a general fertilizing
program be followed, such as outlined in Florida Experiment
Station Bul. 270, and supplemented with summer applications
of nitrogenous materials when advisable.
Several important facts apparently have been emphasized by
the cover crop experiment reported on in this bulletin. First,
a soil condition suitable to pecan tree growth must be main-
tained, otherwise full benefit of commercial fertilizers will not
be obtained. Second, under conditions of soils and trees which
prevailed in the orchard worked with, appreciable increases in
nut production were obtained with sulfate of ammonia applied







Florida Agricultural Experiment Station


Fig. 19.-Austrian peas and hairy vetch growing on Bladen fine sandy
loam soil in a pecan orchard near Baldwin, Duval County.


S/

IX


Fig. 20.-Austrian peas growing in pecan variety orchard, Experiment
Station Farm, Gainesville.







A Cover Crop Program for Florida Pecan Orchards


where winter and summer legumes were grown each year. Third,
a combination of oats and Crotalaria spectabilis grown during
winter and summer, respectively, did not produce profitable nut
yields, either with or without annual applications of sulfate of
ammonia. Fourth, owing to habits of the pecan, several years
are required to revive weak trees to a point where twig growth
will be sufficient to produce profitable nut yields. Fifth, pecan
varieties vary in their productive ability and therefore it would
be possible to produce profitable returns with a suitable variety
while one unadapted would show a loss.

SUMMARY
An experiment to test the effects of cover crops on growth
and yield of Frotscher and Stuart pecan trees on Norfolk fine
sandy loam soil was conducted at Monticello from 1927 to 1934.
Legumes grown in winter and summer were compared with
combinations of non-legumes in winter and legumes in summer,
and with no planted cover crops. Superphosphate and sulfate
of potash were applied in the fall broadcast over the entire
experimental area when the seed were planted. Sulfate of am-
monia applications were made in the summer to half of each
plot to test its effect on growth and production of pecan trees
with and without the different cover crops.
Cover crops of legumes in winter and summer caused signifi-
cant increased production of pecans in the experiment. The
combination of a non-legume in winter and legume in summer
failed to prove satisfactory, and nut yields generally were lower
than in the plot where no planted cover crops were grown.
A nitrogenous fertilizer, sulfate of ammonia, applied during '
the summer generally caused higher nut production. The in-
'creases, however, were significantly greater in the all-legume
plots than with the other treatments.
Frotscher trees responded better than Stuart and produced
decidedly heavier crops of nuts. However, with both varieties
there were no marked differences in yields until after cover
crops had been annually returned to the soil for four years.
An improvement in condition of the soil was obtained where
legumes were grown. This was shown in increased nitrogen
content and heavier growth of Sudan grass produced in the soil
samples and in greatly increased nut production.







Florida Agricultural Experiment Station


LITERATURE CITED

1. BLACKMON, G. H. A partial report on some of the pecan investigations
being carried on by the Florida Agricultural Experiment Station.
Nat. Pecan Assn. Bul. 27; 44-48. 1928.

2. Crotalaria as a summer cover crop for pecan orchards.
Nat. Pecan Assn. Bul. 29; 53-59. 1930.

3. BLACKMON, G. H., and R. W. RUPRECHT. Fertilizer experiments with
pecans. Fla. Agr. Exp. Sta. Bul. 270. 1934.

4. CRANE, H. L. Growth and fruiting relations in the pecan. Ga.-Fla.
Pecan Growers' Assn. Proc. 25; 18-25. 1931.

5. FINCH, A. H., and H. L. CRANE. Physiological factors associated with
the productiveness of pecan shoots. Nat. Pecan Assn. Bul. 30; 98-
105. 1931.

6. FOWLER, E. D., and R. D. LEWIS. Some effects of cover crops and
their management on the fertility of Norfolk sandy loam. South-
eastern Pecan Growers' Assn. Proc. 28; 37-46. 1934.

7. GOSSARD, C. A. The importance of maintaining vigorous terminal
growth of pecan trees. Nat. Pecan Assn. Bul. 32; 84-89. 1933.

8. ISBELL, C. L. Growth studies of the pecan. Ala. Agr. Exp. Sta. Bul.
226. 1928.

9. PACE, VERNON. Crotalaria as a summer cover crop for pecan orchards.
Nat. Pecan Assn. Bul. 31; 77-79. 1932.

10. SKINNER, J. J., and J. B. DEMAREE. Relation of soil condition and
orchard management to the rosette of pecan trees. U. S. D. A.
Dept. Bul. 1378. 1926.

11. STOKES, W. E., R. M. BARNETTE, H. W. JONES and J. H. JEFFERIES.
Studies on summer cover crops in a Pineapple orange grove. Fla.
Agr. Exp. Sta. Bul 253. 1932.

12. WARNER, J. D. Date of seeding and phosphate requirements of winter
legumes and their effect upon subsequent crops. Fla. Agr. Exp.
Sta. Report 1932; 46-47.




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