The fundamentals of fruit production

Preface

Fruit growing in the United States is so widespread and so diversified that no work of ordinary dimensions can codify it on the basis of empirical practices, which differ from place to place. The fundamental factors, however, are always the same and once they are understood, the adaptation of practices to local conditions presents little difficulty.

The present work attempts to focus attention on the conditions which make the fruit plant profitable; practices are considered only as they affect these conditions, not as ends in themselves. Maintenance of this point of view has necessitated a rather wide departure from conventional arrangement of subject matter. The common orchard practices are not sacred in themselves; indeed, they are important only in so far as they help vegetative growth and especially fruit production. Fundamentally the plant's growth and functioning depend on the nature of the environment and the adjustment thereto and not directly on cultural practices, which only modify the relation of the plant to the environmental complex. Consequently these practices appear inconspicuous in the Chapter and Section headings.

Acquaintance with principles without the facts on which they rest is itself empirical. Particular attention, therefore, is given to the inclusion of sufficient illustrative matter to permit quantitative estimate of the validity and applicability of the principles enunciated. Comparatively little that is original is presented; much of the material that is novel to pomological texts is included because of its inaccessibility to the average student. Many significant observations which have been neglected because their ultimate bearing was not appreciated at the time they were recorded, have been reviewed in the light of modern knowledge. Plant physiology, plant chemistry, soil science and physics have been requisitioned freely and advisedly; in no case, however, without an indication of applicability to pomology. Careful consideration has approved this course because special applications to fruit growing are rare in the general University courses in these subjects and because in the arrangement of many curricula, pomology precedes some of the science courses which are needed as preparatory training. Though every effort is made to insure thoroughness, exhaustiye treatment is not attempted, since it would be useful to few readers.

The solution of a problem arising outside of the classroom depends on obtaining all the pertinent data, systematizing them to ascertain the factors involved and applying to the problem th.e knowledge so gained.

vi PREFACE

This text is designed to prepare the student to undertake these steps. As with any text, much is necessarily left to the instructor, particularly matters of opinion and of local application.

Finally, it hardly need be said that this text is intended for students of college grade. It is not a manual on how to grow fruit; it does not attempt to enter fields best covered by classroom discussion, laboratory work or practical experience. It is intended, however, to be a supplement and guide to these.

The writers wish to express their appreciation of the helpful criticisms and suggestions offered by those to whom portions of this manuscript have been submitted: to Dr. M. M. McCool of the Michigan Agricultural Experiment Station (the Section on Water Relations); to Dr. William Crocker of the University of Chicago and to Dr. E. J. Kraus of the University of Wisconsin (the Section on Nutrition) ; to Dr. W. H. Chandler of Cornell University (Chapters 14-18, dealing with Winter Injury) ; to Dr. 0. M. Stewart, Professor of Physics in the University of Missouri and to George Reeder of the U. S. Weather Bureau (Chapters 19 and 20 on Frost Occurrence and Control) ; to Prof. Ray Roberts of the University of Wisconsin (the Section on Pruning) ; to Dr. M. J. Dorsey of the University of Minnesota (the Section on Fruit Setting) ; to Prof. W. P. Tufts of the University of California, to Dr. J. K. Shaw of the Massachusetts Agricultural Experiment Station and to Paul C. Stark of the Stark Bros. Nursery Co. (the Section on Propagation) ; to Prof. Roy E. Marshall of the Michigan Agricultural College and to Prof. W. P. Tufts of the University of California (Chapters 34 and 35 on Orchard Locations and Soils); finally to Dr. C. V. Piper. Many valuable criticisms and suggestions have been incorporated in the text. In a few instances the writers have believed themselves justified in adhering to their original interpretations of the evidence, so that these authorities who have assisted the writers very materially are not to be held responsible for any part of the book in its present form.

Acknowledgment is made also to Prof. C. E. Shuster of the Oregon

Agricultural Experiment Station for Figures and to Dr. J. K. Shaw of the

Massachusetts Agricultural Experiment Station for Figure 56.

Columbia, Mo. The AUTHORS.

August, 1921.

Contents

Page

Preface v

Chapter I

Water as a Plant Constituent — The Water Requirements of Plants in Terms of Dry Weight — The Water Requirements of Plants in Terms of Precipitation — Amounts Used by the Plants Themselves; Total Amounts Required for Plants and to Compensate for Evaporation, Runoff and Seepage — Planting Distances Related to Moisture Supply — Factors Influencing the Water Requirements of Plants — Nutrient Supply; Cultivation; Light; in General; Some Applications to Practice — The Wilting Point for Fruit Plants — Wilting Coefficients; Wilting under Field Conditions; Wilting Coefficients and Drought Resistance — Summary.

Chapter II

Water Absorption — The Water Absorbing Organs — The Handling and Transplanting of Nursery Stock — The Water Absorbing Process — Factors Enabling the Roots to Exploit the Soil; Adaptation of Roots to Moisture Conditions; Factors Influencing Rate of Absorption; Submergence and Root Killing— Transpiration — Cuticular and Stomatal Transpiration Compared; Variability in Number of Stomata in Accordance with External Conditions — Factors Influencing Rate of Transpiration — Character of Cuticle; Age of Leaf; Defoliation, Summer Pruning; Wind Velocity, Windbreaks; Light; Temperature, Slope of Ground — The Water Conducting System of the Tree — Summary.

Chapter III

Orchard Soil Management Methods and Moisture Conservation ... 31 Orchard Soil Management Methods Defined and Described — Orchard Soil Management Methods and Surface Run-off — Moisture Under Tillage and Sod-Mulch Systems of Management — Some New York and Pennsylvania Records; Some New Hampshire Records; English Experience; Some Kentucky and Kansas Records; in General; Practicability of Sod-mulch System Influenced by Depth of Rooting — Influence of Depth and Frequency of Cultivation upon Soil Moisture — Intercrops and the Soil Moisture Supply — Cover Crops and the Moisture Supply — Effects of Early and Late Seeding; Winter-killed and Winter-surviving Cover Crops — Wind Velocity and Evaporation, Windbreaks — Summary.

vii viii CONTENTS

CHAPTER IV Page

Soil Moisture: Its Classification, Movement and Influence on Root

Distribution 47

Classification of the Water in Soils and Plant Tissues — The Response of Water to the Force of Gravity and the Evaporating Power of the Air; the Relative Saturation; Resistance to Freezing — Movement of Water in the Soil — Percolation; the Rise of Water by Capillarity; Lateral Movement of Water in the Soil — The Distribution of Fruit Tree Roots as Influenced by Soil Moisture — The Idea 1 Root System — Specific and Varietal Differences in Root Distribution — The Distribution of Tree Roots under Varying Conditions — In the Hood River Valley, Oregon and in Ohio; in a Gravelly Loam, Underlaid by Hardpan, in Maine; in a Thin Gravelly Loam, Underlaid by Rock, in Maine; in Dwarfs; the Influence of Soil Moisture; the Influence of Cultivation; the Influence of Soil "Alkali" — Applications to Orchard Practice — Summary.

CHAPTER V The Response of Fruit Plants to Varying Conditions of Soil Moisture

and Humidity 66

Influence of Soil Moisture on Vegetative Growth — New Shoots and their Leaves; Annual Rings and Trunk Circumference; Moisture Supply and the Growth Period in Early Spring; the "Second Growth" of Midsummer or Late Summer — Influence of Water Supply on the Development of Fruit — Size; Yield; Shape and Color; Composition; Disease Resistance and Susceptibility — Residual Effects of Soil Moisture — On Vegetative Growth; on Yields — Influence of Atmospheric Moisture on Growth— In General; Russeting of Fruit; Fruit Setting — Summary.

CHAPTER VI Pathological Conditions Associated with Excesses and Deficiencies in

Moisture 83

Disturbances Due to Moisture Excesses — The Splitting of Fruit; (Edema; Fasciation and Phyllody; Chlorosis; Rough Bark or Scaly Bark Disease; Watercore — Disturbances Due to Moisture Deficiencies — Defoliation, Premature Ripening of Wood — Dieback — Cork, Drought Spot and Related Diseases — Fruit-pit; Cork; Surface Drought Spot; Deep-seated Drought Spot; Dieback and Rosette; Bitter-pit; Jonathan-spot; Black-end — Silver Leaf — Lithiasis — Summary.

Chapter VII

Distribution of Elements Found in Ash — In Tissues of Different Kinds; in Tissues of Different Age; at Different Seasons — Absorption — The Osmotic System — Displacement — Availability of Ash Constituents — Availability and Solubility Distinguished; Factors Influencing Solubility; Availability of

CONTENTS IX

Page Phosphorus; Availability Varies According to Kind of Plant; Availability of Iron and Sulfur — Availability of Nitrogen — Nitrification — Aided by Liming; Influenced by Methods of Soil Management; Influenced by Temperature and Soil Moisture — Losses of Nitrogen from the Soil — Maintaining the Nitrogen Supply of the Soil — Nitrogen Fixation — Soil Reaction, Acidity and Alkalinity — Soil Reaction and the Availability of Phosphorus; Soil Reaction and the Availability Of Iron; Acid Tolerance of Certain Crops — Concentration, Soil "Alkali" — Tolerance of Different Fruits; Injuries from Excessive Fertilization; some effects of Soil Alkali; Remedial Measures — Soil Toxicity — General and Specific Effects; Protecting Against Toxins; Importance in the Fruit Plantation — Antagonism; Aeration; Selective Absorption — Transpiration — The Nutrient Requirements of Crop and Fruit Plants — Summary.

Chapter VIII

Nitrogen — Synthesis of Organic Nitrogenous Compounds — Translocation and Use of Elaborated Nitrogenous Compounds — Seasonal Distribution of Nitrogen — In Leaves; in Branches, Trunks and Roots; in Spurs; in Fruit; in Various Tissues of Trees of Different Age — Phosphorus — Synthesis of Phosphorus-contain : ng Organic Compounds — Translocation and Use of Phosphorous-containing Compounds — Amounts Used in Fruit Production — Seasonal Distribution of Phosphorus — In Leaves; in Branches, Trunk and Roots; in Spurs; in Fruit; in Various Tissues of Trees of Different Ages — Potassium — Synthesis, Translocation and use of Potassium-containing Compounds — The Demand and the Supply — Seasonal Distribution of Potassium — In Leaves; in Branches, Roots and Trunks; in Spurs; in Fruit; in Various Tissues of Trees of Different Age — Sulfur — Iron — Magnesium — Calcium — Seasonal Distribution of Calcium — In Buds and Leaves; in Bark and Wood; In Fruits — The Demand and the Supply — Other Mineral Elements — Silicon; Sodium; Chlorine; Aluminum and Manganese — Summary.

Chapter IX

Assimilation and Limiting Factors Defined — Carbon Assimilation — Factors Involved — Carbon Dioxide; Water; Light — Leaf Pigments — Variation with Age; Variation with Light Supply — Temperature; Enzymes — Products — Oxygen — Carbohydrates — Daily and Seasonal Fluctuation in Leaves; Forms of Storage — Seasonal Fluctuations of Stored Carbohydrates — Easily Hydrolizable Carbohydrates; Starch; Sugars — Carbohydrate Utilization — . In Tissue Building; in Retaining Moisture; Increasing Osmotic Concentration; as a Source of Energy; Relation to Pigment Formation — Summary.

Chapter X

The Development of the Fruitful Condition — The Response of the Plant to Changes in Relative Amounts of Nitrogen and of Carbohydrates — The Significance of Carbohydrate Accumulation, Manufacture in Excess of Utilization — In Fruit Spurs; Influence of the Nitrate Supply; Influence of the Moisture Supp'y; Influence of Other Factors — Fruit-bud Formation — x CONTENTS

Page Evidence of Differentiation — Time of Differentiation — In Relation to Position; Varietal Differences; Differences Induced by Cultural Treatment — Abnormalities; Winter Stages — Summary.

Chapter XI

Surpluses— Nitrogen; Magnesium; Copper; Arsenic; Manganese; Other Elements — Deficiencies — Nitrogen; Phosphorus and Potassium; Sulfur; Iron; Magnesium and Calcium; Chlorine — Analysis of the Fertilizer Problem — The Fertilizer Requirements of the Orchard.

Chapter XII

The Influence of Nitrogenous Fertilizers on Vegetative Growth — In Peaches; in Apples; in Strawberries; Negative Results, Nitrogen not a Limiting Factor — Influence of Nitrogen on Blossom-bud Formation — in Peaches; in Apples — Influence of Nitrogen on the Setting of Fruit — Influence of Nitrogen on Size of Fruit — Influence of Nitrogen on Color of Fruit — Influence of Nitrogen on Yield — The Correlation Between Vegetative Growth and Yield — Influence of Nitrogen on Composition and on Season of Maturity — Summary.

CHAPTER XIII Fertilizers, Other Than Nitrogenous, in the Orchard 218

The Indirect Effects of Fertilizers — Phosphoric Acid; Sulfur; Lime — Plant Nutrient Carriers, Different Forms of Fertilizers — Nitrogen from Inorganic Sources; Nitrogen from Organic Sources; Phosphorus; Potassium; Sulfur; Lime— Season for Applying Fertilizers — The Relations of Seasonal Conditions to Response From Fertilizers — Summary.

Chapter XIV

Heat Units — The Relative Values of Different Effective Temperatures — Influence of Latitude on Heat Requirements — In the Early Harvest Apple; in the Elberta Peach; in Chestnut Blight — Variations in Heat Requirements from Season to Season — Acclimatization to Varying Amounts of Heat — In General — Optimum Temperatures — Variation within the Species or Variety; Differences within the Variety for Separate Processes; Variation in Quality with Amount of Summer Heat; Variation in Season of Maturity with Amount of Summer Heat — Soil Temperatures — Indirect Temperature Effects — Summary.

CONTENTS xi

CHAPTER XV Page

Death from Freezing — Tissue Freezing is Accompanied by Cell Dehydration; Freezing, Not Cold, Kills; Freezing and the Deciduous Habit — Increasing Hardiness — By Increasing Sap Density — By Increasing Water-retaining Capacity — Water-retaining Capacity Associated with Pentosan Content — Water Soluble Pentosans in Particular — Pentosan Content, Water-retaining Capacity and Hardiness Responsive to Environmental Conditions — Increased Hardiness with Increased Maturity — Rapid Temperature Changes — Killing with Slow and with Rapid Freezing; Slow and Rapid Thawing — Variation in Critical Temperatures — Summary.

Chapter XVI

Conditions Accompany Winter Injury; Winter Injuries Classified — Injuries Associated with Immaturity — Affecting More or Less the Entire Plant — Tender Plants May be More Resistant Than Hardier Plants; the Effect of Summer Conditions Favorable for Late Growth ; Second Growth Particularly Susceptible; Preventive Measures — Localized Injuries — Crotch and Crown Injury; Localized Injuries and Delayed Maturity; Contributing Factors; Remedial Measures — Winter Injury Associated with Drought — Immaturity and Winter Drought — Water Loss from Dormant Tissues — Water Conduction in Trees during the Winter — Relation of Freezing to Water Conduction — Where Winter Drought Conditions Prevail — Protection against Winter Drought Injuries — Winter Irrigation — Cultivation; Cover Crops — Windbreaks — Effect of Wind Velocity; Effect on Evaporation; Effect on Soil Moisture — Injuries Characteristic of Late Winter Conditions — The Rest Period — Injuries to Fruit Buds — Changes in Water Content of Buds during Winter — Contributing Factors — Protective Measures — Pruning; Fertilization and Cultivation; Thinning; Whitewashing and Shading — In General — Injuries to Vegetative Tissues — Distinguished from Summer Sunscald and Injuries Associated with Immaturity; Moisture and Temperature Conditions in the Affected Parts; Preventive Measures — Injuries Due to Sudden Cold — General Effects; Trunk Splitting — Summary.

Chapter XVII

Soil Temperatures in Winter; Critical Temperatures for Tree Roots — Factors Influencing Frost Penetration — Protection Afforded by Snow; Different Systems of Soil Management; Soil Type; Soil Moisture — Relation of Cover Crops to Root Killing — Root Killing in Different Fruits — The Apple; the Pear; the Peach; the Cherry; the Plum; the Grape; the Small Fruits — Preventive and Remedial Treatments — Deep Planting and Mulching; Use of Hardy Stocks; Pruning; Handling Nursery Stock in Cold Weather — Summary.

Chapter XVIII

The Apple — Injuries Associated with Immaturity; Control Measures; Varietal Differences — The Pear; the Peach; the Cherry; the Plum; the xii CONTENTS

Page Grape — The Small Fruit — Immaturity Most Important — Relation of Summer Pinching to Maturity; Varietal Differences from Year to Year — Injuries from Drought not Uncommon — Group and Varietal Characteristics — Summary.

Chapter XIX

Frost Formation — Frost and Freezes Distinguished — Relation of Radiation to Frost — Temperature Inversion; Radiation and Thermometer Readings; Radiation and Plant Temperatures — Dewpoint and its Relation to Frost; Relation of Clouds and Wind to Frost Occurrence— Influence of Location on Danger from Frost — The Blossoming Season and Latitude; Average Date of Last Spring Frost and Latitude; Average Dates and Frost Danger; Determining Frost Risks in Different Sections and Localities — Influence of Site on Minimum Temperatures — Minor Factors Affecting Temperature — Minor Differences in Elevation; Influence of Soil; Influence of Soil Covering; Influence of Soil Moisture; Effect of Cultivation; Significance, Particularly in Small Fruit Culture — Summary.

Chapter XX

Critical Temperatures — At Different Stages of Blossom Development; Varietal Differences; Vigor and Recuperative Ability; Weather Conditions before and after Freezing; Signs of Damage; Frost Injury and the Size of the Crop — Avoiding Frost through Late Blossoming Varieties — Blossoming Range Varies with Earliness; Blossoming Period and Fruit Bud Position; Retarding Blossoming; Indices to Blossoming Periods in New Locations — Frost Prediction — Relation of Dewpoint to Minimum Temperature; Weather Bureau Methods; Local Interpretation of Key Station Predictions — Frost Fighting — Smoke Screens to Reduce Radiation — Covering and Spraying — Orchard Heating — Heat Units in the Fuel; Height of the Ceiling Layer; Effect of Wind; Conditions Determining Practicability — Frost Effects — Summary.

Chapter XXI

Pruning for Form, Training — General Objects — Details in Training — Height of Head; Number of Scaffold Limbs; Distribution of Scaffold Limbs; Open and Closed-centered Trees; Trees of Different Shape; Lowering the Tops of Trees; Elimination and Subordinating Limbs; Preventing the Formation of Crotches — Bearing Habits — Relation of Growth Habits to Position of Fruit Buds; Different Kinds of Flower-bearing Shoots — A Classification of Plants According to Bearing Habits— Groups I-IX (Inclusive) — The Relation of Fruiting Habit to Alternate Bearing — Possible Causes of Different Bearing Habits — Summary.

CONTENTS xiii

CHAPTER XXII Page

Influence on Size of Tree — Amount and Character of New Shoot Growth; Leaf Surface and Root System — Influence on Fruit Spur and Fruit Bud Formation — Influence on Leaf Area and Fruit Size — Pruning as a Cause of Abnormal Structures — Amount of Pruning Varying with Fruiting Habit — Summary.

Chapter XXIII

Heading Back and Thinning Out — Influence on New Shoot and New Spur Formation; Influence on General Shape and Habit; Influence on Fruit Bud Formation and Fruitfulness; Thinning and Heading Lead to Different Nutritive Conditions; the Places of Thining and of Heading in Pruning Practice — Fine, as Compared with Bulk Pruning — Results following Dehorning; Results Attending the Removal of a Few Large Limbs; Results Attending Spur Pruning; Application to Practice — Root Pruning — Special Pruning Practices — Summary.

Chapter XXIV

Pruning at Different Times during the Dormant Season — Summer Pruning — Influence on Vegetative Growth; Influence on Production; Summer Pruning to Develop Framework; Summer Pruning as a Conservation Measure; Influence on New Spur Formation; Influence on Fruit Bud Formation; Influence on Fruit Color — Summer Pinching — Summary.

Chapter XXV

Pruning the Apple and the Pear — The Formation of Fruit Spurs; Retaining Spurs Already Established; Keeping Spurs Strong and Vigorous; Summary of Usual Pruning Treatment; Special Suggestions for Unusual Fruiting Habits — Pruning the Peach — When and How Severely; Pruning to Secure Most Favorable Location of Fruiting Surface — Pruning the Sweet Cherry; Pruning the Almond, Apricot, Plum and Sovir Cherry; Pruning the Currant and Gooseberry; Pruning the Brambles — Pruning the Grape — Severity of Pruning; Kind of Pruning; Methods of Training.

CHAPTER XXVI The Structures and Processes Concerned in Fruit Setting 475

The Ovule — The Embryo Sac — Pollen — Pollination — Germination of the Pollen Grain — Course of the Pollen Tube; Time for Pollen Tube Growth — Fertilization — Secondary Fertilization; Development of the Embryo and xiv CONTENTS

Page Endosperm — The Setting of the Fruit — What Constitutes a Normal Set of Fruit — The June Drop and Other Drops — The First Drop; the Second Drop; the Third Drop or June Drop — Fruit Setting, Fruitfulness and Fertility Distinguished — Sterility and Unfruitfulness Classified — Summary.

Chapter XXVII

Due Principally to Evolutionary Tendencies — Imperfect Flowers, Dioecious and Monoecious Plants; Heterostyly; Dichogamy, Protandry and Protogyny; Impotence from Degenerating or Absorbed Pistils or Ovules; Impotence of Pollen — Due Principally to Genetic Influences — Sterility and Unfruitfulness Due to Hybridity — Incompatibility — Interfruitfulness and Interfertility; in Reciprocal Crossings — Due Principally to Physiological Influences — Unfruitfulness Due to Slow Growth of the Pollen Tube — Premature or Delayed Pollination — Nutritive Conditions Within the Plant — Effect on Pollen Viability; Effect on Defectiveness of Pistils; Fruit Setting of Flowers in Different Positions; Strong and Weak Spurs; Evidence from Ringing Experiments; Evidence from Starvation Experiments — Summary.

Chapter XXVIII

Nutrient Supply; Pruning and Grafting; Locality — Season — End-season Fertility; Change of Sex with Season — Age and Vigor of Plant; Temperature; Light; Disturbed Water Relations; Rain at Blossoming; Wind; Fungous and Bacterial Diseases; Spraying Trees When in Bloom; Other Factors That Cause the Dropping of Fruit and Flowers — Summary.

Chapter XXIX

Factors more Directly Concerned in the Development of the Fruit . . 521 Stimulating Effects of Pollen on Ovarian and Other Tissues; the Effect of Certain Stimulating Agents on Fruit Setting — Seedlessness and Parthenocarpy — Seedlessness of Non-parthenocarpic Fruits; Vegetative and Stimulative Parthenocarpy; Relation of Anatomical Structure of Fruit to Parthenocarpy; the Value of Seedless and Parthenocarpic Fruits — The Relation of Seed Formation to Fruit Development — Structure of Fruit; Form; Size; Composition and Quality; Season of Maturity; Specific Influence of Pollen on Resulting Fruit — Summary.

Chapter XXX

The Number of Pollenizers; Temporary Expedients; Pollinating Agents — The Fruit Setting Habits of Different Fruits — Apple; Pear; Quince; Peach; Almond; Plum; Apricot; Cherry; Grape; Strawberry; Currant and Gooseberry; the Brambles; the Nuts; Persimmon — Summary.

CONTENTS XV

CHAPTER XXXI Page

The Congeniality of Grafts— Congeniality and Adaptability Distinguished— The Influence of Stock on Cion — Stature; Form — Seasonal Changes — End-season Effects, Ripening of Fruit; Maturity of Wood; Spring Effects— Hardiness— Disease Resistance— Physiological Diseases— Yield— Fruit-bud Formation; Fruit Setting; Size of Fruit— Quality— In Pomaceous Fruits; In Stone Fruits; in Grapes; Qualitative Differences and Quantitative Variations — Longevity; General Influence of Stock on Cion — Influence of Cion on Stock — Size and Number of Roots; Distribution and Character of Roots; Longevity, Growing Season and Hardiness; Other Influences; in General.

Chapter XXXII

Conflicting Interests of Nurseryman and Fruit Grower — Adaptation of Stocks to Particular Conditions — Adaptation to Soil Temperatures; Adaptation to Soil Texture and Composition; Immunity or Resistance to Soil Parasites — Propagation by Cuttings — Advantages and Disadvantages — Grapes in Particular; Apples and Pears— Propagating Apples and Pears by Layerage and Hardwood Cuttings— Varietal Differences and Contributing Factors — Sources of Nursery Stock— Grades of Nursery Stock— Selection of Seedling Stocks; Grafted or Budded Trees; Double Worked Trees— Pedigreed Trees- Some Results in Citrus Fruits; Some Results in Apples; in General.

Chapter XXXIII

Life Zones, Crop Zones and Fruit Zones— The Boreal Zone; the Tropical Zone— Austral or Temperate Zone— Transition Zone; Upper Austral Zone; Lower Austral or Sub-tropic Zone— Geography of Fruit Production as Influenced by Temperature— Peach Growing as Influenced by Temperature; Grape Growing as Influenced by Temperature; Temperature and the Geographic Range of Apple Varieties; the Effect of Bodies of Water on Temperature; Influence of Altitude on Air and Soil Temperatures- Geography of Fruit Production as Influenced by Rainfall and Humidity — Other Factors Influencing the Geographic Distribution of Fruits— Sunshine; Parasites; Wind; Native Range of Parent Species; Length of Time in Cultivation; Uses and Quality of Product; Relation to Consuming Centers and Transportation Facilities — Summary.

CONTENTS xvi

CHAPTER XXXIV Page

Orchard Locations and Sites. . . . . , g g ' ' { Gr0 wing Section; Land Orcharding in or outside * Jjj™^ d Aspect _l n fluence on Soil Tern- Values; ^^T^t^XZTon Fruit Growing; Indirect peratures and on the Plant Speed* ^ f Elevation _Ther-

Effects; Abruptness of Slope-A ^ r -T n fluence of Distance from Water; m al Belts-lnfluence ^«^% a £. Indirect Temperature Effects; Influence of Size and Shape otBodyo , Winter ; Obstructions-

Minor Temperature ^^^^ ^ ture; Evaporation, Rainfall Local Variations and their Significance iei y

and Other Factors— Summary.

Chapter XXXV

Orchard Soils. . . • • ■ ■ • ' ' " ' Phvsica i Condition— Requirements of Considered from the Standpoint of ^!%^ cat[on of Soils acc0 rding Different Crops; Requirements as to Depth C - Slhca ^ to Size of Soil Particles; Mechanical Analyse , otVa mentg

Considered from the Standpoint of Chenncal Compoait 1 on q

of Different Crops-Chenucal £*£,£ J^J^Vegetation

dence on Soil ^^/^JT^ of Varieties to Particular as an Index to Crop Adaptation— Adaptation 01 as an Index to

Soils— Summary.

Glossary Index. .

674 679

N

THE FUNDAMENTALS OF FRUIT PRODUCTION

Section I Water Relations

The importance of moisture as a factor in the production of fruit is appreciated only in part. In arid sections the lack is obvious; in many regions certain lands are recognized as too moist for fruit plants. In the majority of the so-called humid sections, however, there is a tacit assumption that nature provides satisfactorily for the requirements of fruit plants. Drought may diminish or destroy other crops, but as long as trees survive there is considered to be sufficient moisture.

The forest trees, relied on as evidence of this sufficiency, show, even in a limited area, striking differences in vigor, according to their locations. One of the most important factors recognized by the forester as affecting tree growth, is moisture. Certain spots even in humid regions, are chronically dry, some are nearly always wet; others, favorable in some seasons, are subject rather frequently to excess or deficiency of moisture.

Much of the complacence concerning the water supply of trees is based on the supposedly great range of their roots and the consequent great amount of soil from which they can draw water. For this reason a statement of the extent to which forest trees actually deplete the soil moisture is pertinent. Zon 139 cites data showing moisture contents in June of 4.5 and 4.8 per cent, respectively at 4 and 8 inches in soil through which forest tree roots were ranging, while adjacent spots within the forest, exactly similar except that the roots had been excluded contained, at the same depths, 13.8 and 11.0 per cent, respectively. At 16 inches the root free soil had over twice as much moisture as that to which the roots had access. Evidence is cited to the effect that the water level is lowered under forest and that with the removal of the forest the water level rises. Zon considers that the inability of many species to grow under an established cover of trees, commonly called shade intolerance, is in reality due to the low supply of moisture in the soil. When the roots of the top growth are excluded from an area, the intolerant species grow there with considerable vigor.

Deficient and excessive moisture are admittedly each a limiting factor in crop production. Table 1, based on estimates by crop reporters of the United States Department of Agriculture, shows the damage caused by injurious moisture conditions in comparison with other factors. The figures on apples and berries are averages for the period 1912-1919 and on other crops selected in comparison for the period 1909-1919. According to these estimates small fruits suffer more from drought than from any other single factor, while apples are injured more only by cold weather.

Table 1. — Damage to Crops from Different Causes

(After Smith 1 ")

a u 2 m 'o

'S

1 8.

Q

Excessive moisture, per cent.

a

a o

ft

■§ o o

E

<o

M

o a

<D

O <D »- ft a <u a

h

<u ft

'3

H a

a

M

a

ft o

H aj

h

ft

1 u

o ft

u

a u o

ft

» 03

en

s ° ft

GO ft m a

a o u

a ft ft

"3 ft o J;

.2 e Q S c o

a

ft

"oS O

12.4 16.3

6.7 14.4

8.7 12.3

5.4

9.3

0.4

0.1 0.8 0.5 0.8 0.5

22.9

0.2 0.2 0.3 0. 1

0.1 0.1

0.2 .0.7 0. 1 0.3 0. 1 0.2

28.8

Corn

Rice

Potatoes

31.1 19.0 30.0 20.5

Cotton

Berries

35.5 39.6 24.9

Precipitation cannot be controlled. Soil moisture, however, is susceptible more or less to modification by various practices and adjustments of fruits or of stocks for fruits can be made in some cases to the moisture conditions of the soil. For these reasons recognition of soil conditions, understanding of the water requirements of the various fruit plants and knowledge of the relation of various cultural practices to moisture control are of fundamental importance to the fruit grower.