Subtropical vegetable-gardening

Front matter

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Preface

We may regard the successful growth of the orange tree as marking the outer limit of the subtropical regions, where frosts are of short duration and the year is divided into hot and cool seasons. The coconut palm marks the boundary of the outer tropical belt, which has also more or less distinct cool and hot seasons, but as a rule no frosts. The equatorial belt, on the other hand, has no distinct cool season. In the subtropical regions, tropical vegetables may be grown well in the hot season, and temperate vegetables, which can survive any slight frosts that may occur, can be very successfully raised in the cool season. In the outer tropical or trade-wind belts, some temperate vegetables can be grown fairly well in the cool season. In the subtropical and especially in the tropical lands, an elevation of a few thousand feet produces a remarkable change in the climate ; and temperate vegetables can be cultivated at such a height even in the equatorial belt, and still more successfully towards the borders of the tropical belt. Thus the subtropical regions can grow at different times of the year and at different heights, nearly all the vegetables of the world. Except in North India, where numbers of Europeans have resided for a long time, and in certain subtropical countries like peninsular Florida, it is probable that the vi Preface

growing of temperate vegetables in the cool season has not been carried to the extent to which it is capable. With a sufficient demand, good crops of many of the improved temperate vegetables can be raised even in the intertropical regions, either in the lowlands in the cool season, or preferably at elevations of a few thousand feet.

The directions in this book are based mainly on Florida practice, but the publications of the United States Experiment Stations, and of the United States Department of Agriculture, together with the horticultural literature of the tropical countries, have been laid under contribution.

The fertilizer formulas given in the book are such as have been successful in certain cases, but must be regarded as tentative only. A vegetable-grower, by trying different mixtures on his own soil and crop, may improve the formulas which the experience of others gives him as a starting point. Exact or definite formulas are to be regarded only as guides or suggestions, and never as prescriptions. There is so much yet to be done in the application of knowledge to the growing of vegetables, that a useful book on this subject must still consist mainly of results based on experience.

Farmers' Bulletins of the United States Department of Agriculture are sent free on application to the Secretary of Agriculture, Washington, D.C. Other publications of the Department of Agriculture, for which a low price is charged, are obtainable from the Superintendent of Documents, Government Printing Office, Washington, D.C.

The Bulletins of the State Experiment Stations are

Preface vii

sent free (if not out of print) on application to the Directors of the various Stations.

The Experiment Stations for the southernmost states are at the following places : Texas, College Station ; Louisiana, Baton Rouge ; Mississippi, Agricultural College ; Alabama, Auburn ; Florida, Gainesville ; Georgia, Experiment ; South Carolina, Clemson College. The Experiment Stations at Mayaguez, Porto Rico, Santiago de las Vegas, Cuba, and Honolulu, Hawaii, have published bulletins of special interest.

I am indebted to the Florida Experiment Station for most of the illustrations used in this book. Photographs for Plates IX, XV, and XVI were furnished by Dr. D. G. Fairchild, of the Office of Seed and Plant Introduction, at Washington, D. C.

P. H. ROLFS.

Gainesville, Fla., January 1, 1916.

Chapter I Pages

Soils for Vegetable-Gardening in Warm Countries . 1—4

Soils for vegetable-gardening, 1 — Mechanical classification of soils, 2 — Composition of soils, 3 — Elements necessary for plant growth, 3 — Why land becomes poor, 4.

Chapter II

Complete fertilizer, 6 — Sources of nitrogen, 7 — Sources of phosphoric acid, 8 — Sources of potash, 9 — Percentage of fertilizer elements, 10 — Mixing fertilizers, 11 — How to compute the amount of fertilizer in a given formula, 12 — Table of fertilizers, 16 — How to use the table, 17 — Lime, 18 — Ground limestone, 18 — Acidity of Florida soils, 20 — How to test for soil acidity, 20 — How to test a field for fertilizer, 21.

Chapter VII

Coldframes, 52 — Selection of a location, 52 — Construction, 52 — Hotbeds, 55 — Plant-sheds, 57 — Seed-beds and plant-beds, 58 — Preparation of the land, 59 — Well-drained land, 60 — Clearing the land, 61 — Plowing, 61 — Transplanting, 62 — Number of plants to the acre, 65.

Chapter VIII

Poisonous insecticides, 67 — Paris green, 67 — Arsenate of lead, 67 — Zinc arsenite, 68 — Contact insecticides, 68

— Kerosene emulsion, 68 — Whale-oil soap or fish-oil soap, 69 — Soda-sulfur spray, 69 — Tobacco-sulfur spray, 69 — Commercial lime-sulfur solution, self-boiled, 70

— Bean spray, 71 — Miscible oils, 71 — Poison bait, 72

— Gaseous insecticides, 72 — Bisulfide of carbon, 72 — Formalin, 72 — Fungicides, 73 — Bordeaux mixture, 73 — Ammoniacal solution of copper carbonate, 76 — Spraying machines, 75 — Dry materials, 76.

Contents xi

Chapter IX Pages

The packing-house, 78 — Honest packing, 80.

CHAPTER X Vegetables with Edible Leaves or Stems — Cole Crops 81-98 Cabbage, 81 — Seed-bed, 82 — Sowing the seed of cabbage, 82 — Soils for cabbage, 83 — Fertilizers for cabbage, 84 — Preparing cabbage for market, 85 — Marketing cabbage, 85 — Enemies of cabbage, 86 — Varieties of cabbage, 86 — Bulletins, 86 — Brussels sprouts, 87 — Kale or borecole, 87 — Collards, 88 — Cauliflower, 89 — Sowing seed of cauliflower, 90 — Soil and fertilizer for cauliflower, 92 — Setting out the plants, 92 — Cultivation of cauliflower, 93 — Cutting, 93

— Crating cauliflower heads, 93 — Seed production, 94

— Varieties of cauliflower, 94 — Enemies, 95 — Books and bulletins, 95 — Broccoli, 95 — Kohlrabi, 97.

CHAPTER XI Vegetables with Edible Leaves or Stems — Other

Lettuce, 99 — Seed-bed for lettuce, 100 — Preparing the lettuce field, 102 — Cultivation of lettuce, 102 — Fertilizer, 102 — Irrigation for lettuce, 103 — Marketing lettuce, 104 — Lettuce seed raising, 104 — Diseases, 105

— Varieties of lettuce, 105 — Bulletins, 106 — Endive, 106 — Spinach, 107 — Celery, 109 — Soil for celery, 109

— Fertilizer for celery, 111 — Seed sowing, 112 — Transplanting celery, 113 — Irrigation of celery, 116 — Preparing celery for market, 118 — Diseases, 118 — Varieties of celery, 119 — Bulletins, 119 — Chicory, 119 — Parsley, 121 — Cress, 122 — Garden cress, 123 — Upland cress, 123 — Watercress, 123 — Asparagus, 124 — Prep-

Xll

Contents aration of the asparagus plot, 125 — Fertilizer for asparagus, 126 — Planting asparagus, 127 — Cutting, 127 — Bunching and crating asparagus, 128 — Marketing, 128 — Blanching, 129 — Raising asparagus plants, 129 — Canning asparagus, 130 — Enemies, 130 — Varieties of asparagus, 131 — Bulletins, 131 — Globe artichokes, 132.

Chapter XII

Onions, 134 — Soil for onions, 135 — Fertilizer for onions, 135 — Time to sow onion seed, 137 — Seed-bed for onions, 137 — Setting out onions, 138 — Cultivation of onions, 141 — The large-scale method of onion-growing, 142 — Curing the onion crop, 143 — Crating onions, 144 — Raising onions from sets, 144 — Varieties of onions, 144 — Costs in onion growing, 146 — Bulletins, 146 — Leek, 147 — Shallot, 146 — Chive, 149 — Garlic, 150.

134-150

CHAPTER XIII Vegetables with Edible Fruits — The Cucurbits

Cantaloupes, 151 — Soil and preparation, 152 — Fertilizer, 152 — Planting and cultivating muskmelons, 153 — Marketing muskmelons, 153 — Saving melon seed, 153 — Enemies, 154 — Varieties of melons, 154 — Bulletins, 154 — Watermelon, 155 — Soil, 155 — Fertilizer for watermelons, 155 — Planting watermelons, 156 — Cultivating, 157 — Marketing watermelons, 158 — Saving seed, 158 — Diseases and insects, 159 — Varieties of watermelon, 159 — Bulletins and papers, 160 — Cucumber, 160 — Protecting cucumbers from frost, 162 — Soil and preparation of the cucumber field, 163 — Fertilizer for cucumbers, 164 — Cultivating cucumbers, 165 —

151-177

Contents xiii

PAOEB

Picking and packing, 166 — Saving cucumber seed, 167 — Varieties, 169 — Squash, 169 — Choosing the soil for squashes, 170 — Fertilizers, 170 — Fertilizers for squashes, 171 — Planting squashes, 172 — Cultivating, 173 — Marketing, 173 — Varieties, 174 — Chayote, 174

Chapter XIV

Vegetables with Edible Fkuits — Solanaceous Plants 177-208 Tomato, 177 — Tomato seed, 179 — Seed-beds, 180 — Soil for tomatoes, 181 — Fertilizer, 182 — Preparing the tomato field, 182 — Setting out tomato plants, 184 — Cultivating, 185 — Pruning tomato vines, 186 — Staking tomatoes, 187 — Trellising, 188 — Picking tomatoes, 188 — Packing-house, 189 — Sorting tomatoes, 190 — Summer and fall crop, 191 — Saving tomato seed, 191 — Canning, 195 — Enemies of the tomato in Florida, 193 — Varieties of tomatoes, 194 — Literature, 195 — Eggplant, 195

— Hotbeds and coldframes for eggplants, 196 — Using flower-pots, 197 — Soil and preparation, 199 — Fertilizer for eggplants, 199 — Cultivation of eggplants, 200 — Gathering eggplants, 201 — Marketing, 201 — Seed saving, 201 — Varieties of eggplants, 203 — Pepper, 204 — Hotbeds and coldframes for peppers, 205 — Soil and preparation for peppers, 206 — Fertilizer for peppers, 207

— Cultivation of peppers, 207 — Marketing, 207 — Saving seed, 208 — Varieties of peppers, 208.

Chapter XV

Vegetables with Edible Fruits — Other Crops . • 209-221 Roselle, 209 — Propagation, 210 — Cultivation of roselle, 211 — Gathering, 212 — Shipping roselle, 212 — Productivity, 213 — Uses of roselle, 213 — Diseases, 214 xiv Contents

PAGES

— Varieties of roselle, 214 — Bulletin, 214 — Okra, 215— Bulletin, 216 — Plantain, 216 — Papaya, 217 — Bread-fruit, 220.

Chapter XVI

Peas, 222 — Soil and cultivation, 223 — Fertilizer for peas, 223 — Varieties of peas, 224 — Beans, 225 — Bush beans, 226 — Soil for bush beans, 226 — Fertilizer, 226

— Planting and cultivating bush beans, 227 — Preparing bush beans for market, 228 — Harvesting bush beans, 229 — Varieties of bush beans, 230 — Pole beans, 230 — Varieties of pole beans, 231 — Lima beans, 232 — Culture, 232 — Varieties of lima beans, 232 — Runner beans, 232 — Varieties, 233 — Enemies of beans in general, 233

— Bulletins, 233 — Broad bean, 234 — Cowpea, 235 — Bulletin, 235 — Peanut, 236 — Soil and preparation, 236

— Fertilizer, 237 — Planting peanuts, 237 — Cultivation of peanuts, 239 — Harvesting peanuts, 240 — Varieties of peanuts, 242 — Bulletins, 242 — Goober, 242 — Sweet corn, 242.

CHAPTER XVII Vegetables with Edible Tubers or Roots . . . 244-285 Irish potato, 244 — Soil and preparation, 245 — Fertilizer for potatoes, 246 — Seed potatoes, 247 — Planting potatoes, 248 — Cultivation of potatoes, 249 — Harvesting, 250 — Storing potatoes, 251 — Varieties of potatoes, 262 — Second crop of potatoes, 252 — Diseases of potatoes, 253 — Bulletins, 253 — Sweet potato, 254 — Soil for the sweet potato, 254 — Fertilizer, 255 — Propagation of the sweet potato, 255 — Preparation of the land for sweet potato, and transplanting, 256 — Cultivation, 257 — Storing, 258 — Marketing, 259 — Uses, 259 — Enemies, 259 — Varieties of sweet potatoes, 260 — Bulletins, 260 —

Contents xv

Jerusalem artichoke, 261 — Yam, 262 — Radish, 264 — Soil and preparation, 264 — Fertilizer for radishes, 265

— Sowing and cultivation, 265 — Marketing radishes, 266

— Seed raising, 267 — Varieties of radishes, 267 — Comparison of varieties of radish grown in the open garden, 268 — Turnip, 268 — Soil and preparation, 269 — Planting and cultivating, 269 — Marketing, 270 — Varieties of turnip, 270 — Rutabaga, 270 — Beet, 271 — Soil and preparation, 271 — Fertilizer for beets, 272 — Seeding and cultivating beets, 272 — Marketing, 273 — Varieties of beets, 274 — Carrot, 274 — Soil and preparation, 275 — Fertilizer for carrots, 275 — Sowing and cultivation of carrots, 276 — Marketing, 276 — Varieties of carrots, 276 — Parsnip, 277 — Soil and preparation, 277 — Fertilizer for parsnips, 277 — Sowing and cultivating parsnips, 278 — Varieties, 278 — Salsify or oyster plant, 279

— Dasheen or Taro, 279 — Uses of dasheen, 281 — Bulletins, 281— Tanier, 281 — Bulletin, 282 — Horse-radish, 283 — Cassava, 283 — Bulletins, 285 — Lleren, 285.

CHAPTER XVIII Other Vegetables ; Planting-List 286-300

Chenopodium quinoa, 286 — Ullucus tuberosus, 286 — Arracacia Xanthorrhiza, 287 — Yam-bean (Pachyrhizns erosus, and P. tuberosus), 287 — Goa bean (Psophocarpus tetragonolobus), 288 — New Zealand spinach (Tetragonia expansa), 288 — Basella (Basella rubra), 288 — Edible jute (Corchorus olitorius var. edulis), 288 — Edible amaranth (Amaranthus oleraceus, A. gangeticus, and A. viridis), 289 — Para cress (Spilanthes oleracea), 289 — Pigeon pea (Cajanus indicus), 289 — Sword bean and Jack bean (Canavalia), 290 — Chinese cabbage (Brassica Pe-tsai), 290 — Chinese mustard (Brassica juncea), 290 — Roquette (Eruca xvi Contents

PAGES

sativa), 290 — West India cucumber (Cucumis Anguria) ,

291 — Ginger {Zingiber officinale), 291 — Dandelion (Taraxacum officinale), 291 — Asparagus bean (Dolichos sesquipedalis) , 291 — Hyacinth bean (Dolichos Lablab), 292 — Snake gourd (Trichosanthes Anguina),

292 — Tree tomato (Cyphomandra betacea), 292 — Chard (Beta vulgaris var.), 292 — Pepino (Solanum muricatum), 293— Wax gourd, 293 — Planting-list of vegetables by months, 296.

ILLUSTRATIONS

PLATE PAGK

I. Irrigation Opposite 36

Top, wooden sluice for conducting water to cucumbers and other crops, with V-shaped troughs to carry the water and also to be used to protect plants from frost; bottom, sub-irrigation of celery field, showing head-boxes.

II. Lettuce Opposite 99

Top, lettuce grown on a city lot ; bottom, a commercial lettuce field in Florida.

III. Three Good Types of Lettuce . . . Opposite 105

Left, Hanson ; right, Big Boston ; top, Black-seeded Butter.

IV. Celery Opposite 109

Top, largest one well rooted and ready for transplanting ; center, market celery packed in a crate ; bottom, celery packing in field.

V. Plant Beds Opposite 112

Above, a seed-bed for starting celery plants, with cheesecloth covering ; old fertilizer bags on fence were used over the beds to sprout the seeds. Below, a canvas-covered bed in which a cucumber crop is grown.

VI. Celery Opposite 115

Top left, well-grown celery plants (Golden Self-blanching) ; top right, foot-press for packing celery ; bottom, blanching celery by means of boards, xvii xviii Illustrations

PLATE PAGE

VII. Onions, Red Bermuda (left) and Creole. Also a

Hamper of Lettuce ..... Opposite 134 •

VIII. Melons Opposite 151 -'

Top, Rocky Ford muskmelon; bottom, field marked off for muskmelons.

IX. Twelve Varieties of Chatote (Sechium edule). One-third Natural Size ..... Opposite 1H J

X. Eggplants and Peppers .... Opposite 195 V

Top, eggplant plantation ; center left, white eggplant ; center right, eggplant ready for transplanting to the field; bottom, peppers in the field.

XL Cucumber Hampers ; and a Plant of Roselle (Victor

variety) Opposite 209 v/

XII. Potatoes and Tomatoes .... Opposite 244 >> Irish potato field above ; tomatoes properly staked.

XIII. Lettuce and Sweet Potatoes . . . Opposite 257 ^

Top, Big Boston head lettuce, in longitudinal section ; bottom, using disc cultivator in sweet potatoes.

XIV. Root Vegetables Opposite 264 v

Left top, French Breakfast radish ; right top, Long Scarlet radish ; left bottom, Rose Turnip radish ; right bottom, Chantenay carrot.

XV. A Field of Dasheen or Taro as grown in Florida

Opposite 279 v/

XVI. Tubers of Dasheen Opposite 281 >/

About natural size. These tubers weigh four or five ounces.

Chapter I Soils For Vegetable-gardening In Warm Countries

The earthy matter in which plants grow is commonly known as soil ; it is finely pulverized rock intermixed with more or less organic matter. The thin upper stratum in which plants grow is all that we are interested in for the present. The dark color in this stratum is due to the partial oxidation of the vegetable matter here present. The oxygen is mainly derived from the air. The part that is dark is usually called the soil, and that immediately below has been designated the subsoil. The soil is usually more fertile than the subsoil, especially in the South. In some of the alluvial bottoms, the soil is of the same consistency for a considerable depth.

The black vegetable mold in the soil, which we commonly call humus, is an important factor. In it is contained the mineral matter once extracted from the soil by the plants whose rotting produced the humus, in a good condition to be taken up again by other plants. Besides containing food for plants, it keeps the soil in good condition for plant growth. A sandy soil, rich in humus, can withstand a drought better than one in which the humus is wanting ; but unless there is a more or less compact stratum of subsoil below such a sandy soil, much of the fertilizer will be carried off by frequent rains, and the land will be poor. The rotting of vegetable matter is due to friendly bacteria and fungi in the soil. If there are few of these in the soil, any vegetable or animal substance would be of little use to ordinary plants. The bacteria, as it were, pre-digest it. Hence one must take care of these bacteria and not let the soil be too wet, too close, or too acid for them to multiply.

MECHANICAL CLASSIFICATION OF SOILS

Owing to the large percentage of sand in many soils and its presence in all soils, it has been suggested that they should be classified according to the amount they contain. Under this classification there are the following divisions :

1. Clay; from which no sand can be removed by washing.

2. Strong clay ; from which as much as 5 to 20 per cent of sand can be separated.

3. Clay loam ; when washing will remove 20 to 40 per cent of sand.

4. Loam ; when the land contains as much as 40 to 70 per cent of sand.

5. Sandy loam ; from which 70 to 90 per cent of sand can be separated.

6. Light sand; containing more than 90 per cent of sand.

Soils for Vegetable-Gardening in Warm Countries 3

When soil contains an easily perceptible amount of carbonate of lime, it is said to be calcareous or marly.

When a very large percentage of vegetable matter is present, the soil is usually called muck or vegetable mold.

COMPOSITION OP SOILS

Soils that are in good condition for raising crops are made up of about fourteen elements. There are more elements that may occur in soils ; but as only about thirteen of these are actually used by plants, we need not regard the others, with the exception of aluminium, which, although not a plant-food, yet is the chief constituent of all clays.

Elements necessary for plant growth.

The essential elements for plant growth are oxygen, hydrogen, nitrogen, carbon, sulfur, phosphorus, potassium, calcium, magnesium, and iron, together with sodium, silicon, and chlorin. Oxygen, hydrogen, and carbon are mainly, and nitrogen partly, derived from the air. They constitute 95 to 99 per cent of the weight of plants. While these four elements are derived from the air, it should not be understood that they are usually taken directly from it by the plant, nor do they usually enter the plant in the condition of a simple element. All parts of plants, however, take oxygen from the air as they respire, and some plants, belonging to the pea family, are able, under certain conditions, to assimilate more or less nitrogen indirectly from the air. Because the abovenamed four elements make up so much of the weight of plants, it should not be inferred that the other nine elements that are derived from the soil are of only minor importance. Although their combined weight is only from 1 to 5 per cent of the plant, the absence of any of these may materially interfere with its growth. Most vegetables get all their carbon from the air, and they can only get it in the light. They take in most of the other elements along with water by their roots, and they can only continue to do this when water is evaporating out from their leaves. Hence it is seen why they must have enough sunlight.

WHY LAND BECOMES POOR

It will be clear from what has been said that if crops are repeatedly removed from the land, some element or elements will be depleted or exhausted, or, as is ordinarily said, the land becomes poor.

Different crops do not remove an equal amount of the different elements, and even different individual plants of the same crop vary considerably in the amount of any one element that they take from the soil. Some crops take much nitrogen from the soil and return only a part of it when their roots and fallen leaves decay ; others take only a small amount of nitrogen from the soil and give much back ; the former make the land poorer, while the latter make it richer in nitrogen. When a piece of land is " tired " of one crop, it is often able to produce some other crop in fair quantity. To keep soil in such condition that it will produce a crop in paying quantities, we must maintain the necessary elements in sufficient quantity; we must fertilize.

Chapter II Fertilizers

Thirteen of the eighty and more elements now recognized by chemists are more or less directly concerned in the growth of agricultural plants.

Of the thirteen elements, silicon, chlorin, and sodium are perhaps not essential, and are nearly always abundant enough. Oxygen and hydrogen are the elements of water. Carbon is derived directly from the air. Sulfur, calcium, magnesium, and iron are contained in most soils in fair amounts. Only nitrogen, phosphorus, and potassium often become scarce, and the plant must have these three. They play such an important part in the plant economy, and are present in such varying quantities, and so often one or more of them is insufficient in amount, that one looks upon them as the essential elements ; though they are not more necessary to the plant's welfare than some other elements. A deficiency of any one will cause the plants to look sickly, and make them fit subjects for insect and fungous attacks, to which they then readily succumb. If a field has been producing good crops for a number of years and then gradually fails without visible cause, it is a fair indication that some form of food for that crop is becoming exhausted, and one must either stop growing that crop on that particular soil, or in some way supply the wanting plant-foods. This is accomplished by using either home-made or commercial fertilizers. It must not be thought, however, that plants can use up all the mineral food in the soil. They can take only the soluble minerals, and those that happen to come their way. By resting the land, more of the mineral food becomes soluble. The good effects of fertilizers are due mainly to their being soluble plant-food, and to their being put where the plant can get them. Any substance that will supply the deficient element or elements to the soil, in such a form as to be available to the crop, is considered a fertilizer. It is not uncommon to find an element present in the soil in sufficient quantity, but in such form that the crop cannot make use of it; in other words, the element is not available.

COMPLETE FERTILIZER

A fertilizer that contains all three elements, nitrogen (as organic nitrogen, nitrate, or ammonia), phosphorus (as phosphoric acid), and potassium (as potash), is said to be complete. The amounts of the elements vary with the different brands of fertilizer, and should be suited to different crops and the different soils for which they are to be used. The amount of an element in a special fertilizer is governed largely by the amount of that element removed from the soil by any particular crop.

An incomplete fertilizer is one which is wanting in any one or more of the three fertilizing elements. These are known either by their chemical name, as acid phosphate, muriate of potash, nitrate of soda ; or by some trade name, as kainit, blood and bone, guano.

The fertilizer formulae employed in this book should not be regarded as the best under all varying soil conditions. They are suggestive of what will probably prove advantageous under average or normal conditions in a sandy soil. Experience with any particular field or region will soon indicate what changes should be made in a formula for a particular crop. Generally speaking, starch-producing crops, such as Irish potatoes and sweet potatoes, will be benefited by a large quantity of potash.

SOURCES OF NITROGEN

In its natural state, nitrogen occurs as an atmospheric gas, and as such it is not available as a fertilizer. When the amount of nitrogen is mentioned in speaking of a fertilizer, one simply means that it is in some combination with other elements that hold it in the form of a solid.

The different forms in which nitrogen occurs as a fertilizer are : first, as organic matter, either vegetable or animal, for example, cottonseed meal, fish scrap, dried blood, tankage ; second, as nitrate, in nitrate of soda, or nitrate of potash ; third, in the form of ammonia compounds, as sulfate of ammonia. In the guarantees or analyses of fertilizers, when the amount of nitrogen is given, it is intended to imply how much of it would be present if it were in the form of a gas. Sometimes the amount of nitrogen in a fertilizer is expressed as ammonia, when it is really nitrate or organic matter. It is calculated in this way for ease in comparison. This is the method used in Florida.

Nitrogen (or ammonia) is the most expensive fertilizer, the one which is most easily lost by leaching, and also the one an excess or deficiency of which may have the most prejudicial effect on a crop. Hence, it behooves the user to be especially careful with his nitrogenous fertilizers. The cheapest way to secure nitrogen (or ammonia) is to get it free from the air by growing velvet beans or other legumes.

SOURCES OF PHOSPHORIC ACID

A source of phosphoric acid of great commercial importance is the phosphate rock of Florida and South Carolina. This rock contains a varying quantity of phosphoric acid, therefore it is necessary to make an analysis of it before one can know its value. The natural rock becomes soluble only slowly in the soil, so it is customary to grind it and treat with sulfuric acid to make the phosphoric acid readily soluble and available to plants. In this condition it is known as "acid phosphate," or "superphosphate." It has been found of advantage, in some soils, to use the natural rock, finely ground; this is called "floats."

In the manufacture of steel, the phosphorus of the molten iron is oxidized and absorbed by lime. The resulting slag, called "Thomas slag," contains phosphoric acid and much lime. It is not acid but basic, and so is suitable for acid soils, when finely ground.

Another source of commercial importance was phosphate from the bones of various animals. Before the discovery of phosphate rock, this was a very important source ; and while the price of ground bone for fertilizer has not declined much as a result of the discovery of rock phosphate, yet it has not increased as it otherwise would have. In their natural state, bones yield phosphoric acid to plants rather slowly ; but, being crushed and treated with sulfuric acid, the phosphoric acid is made soluble and so becomes available at once or in a short time. But little bone, however, is now treated with acid, and "dissolved bone" has become a trade name for acid phosphate made from rock.

The packing-houses and slaughter-houses collect the bones and harder part of refuse to grind up for fertilizer. Blood and bone is a trade name given to refuse from slaughtering establishments ; its composition is rather indefinite. The bones and refuse of fish in large fisheries, also the carcasses of worthless fish, are used as a supply of this important element of plant-food, as well as nitrogen, under the name of " fish scrap."

SOURCES OF POTASH

In nature, soluble potash usually occurs as a chloride (muriate), a sulfate, or a carbonate. It is also found as an insoluble silicate in many rocks. It is very widely distributed, occurring in all parts of the world, and is one of the fertilizer ingredients that are left after plants are burned ; in other words, it is one of the principal constituents of the ash of plants. Besides this general distribution, it also occurs in large bodies in a very few parts of the earth. The largest and most important of these is located in Stassfurt, Germany, where it is mined, much as salt is in other parts of Europe. In this place it occurs mainly as sulfate mixed with common salt and other substances, and is imported to this country under the name of kainit. When refined, it is sold on our market as muriate of potash or sulfate of potash, as the case may be.

Percentage of Fertilizer Elements

Table showing the approximate amounts of different fertilizer elements in various substances used in growing vegetables

Materials used fob Nitrogen

S & n