Chapter 23

While we have thus dealt principally with the Inorganic or mineral constituents of plants, and the way in which the deficiencies of the soil in respect of any of them may be supplied by artificial applications, we must not ignore the other class of constituents, the Organic. These are supplied almost entirely from the atmosphere itself, though, to a limited extent, the presence in the soil of humus or vegetable matter contributes also. Yet this latter, as seen in the case of land heavily dressed with farmyard or stable manure, vegetable refuse, &c., exercises important functions in other directions. Not only are mineral constituents, in forms available for assimilation, supplied, but soils so treated derive peculiar advantages as regards their mechanical state and improved physical conditions, chiefly in respect of retention of moisture, warmth, &c. Thus, sandy soils, which are very apt, through poverty in humus, to lose their moisture readily and to ‘burn,’ are rendered more retentive of moisture and fertilising constituents by the use of farmyard manure, &c., and have more ‘staple’ or substance given to them, while heavy, tenacious clays are opened out, lightened, and rendered more amenable to the influences of drainage, aeration, &c., and so become less cold and inactive.

For the present purpose the principal garden crops may be grouped in two classes, in accordance with their main characteristics and the predominance of certain of their mineral elements. The figures given on the following page show the average percentage proportions of the several minerals in the ashes of the different plants.

In Class I. Phosphates and Potash predominate. This class consists of the less succulent plants, and includes the following: The Pea: containing, in 100 parts of the ashes, phosphates, thirty-six; potash, forty. Bean: phosphates, thirty; potash, forty-four. Potato (tubers only): phosphates, nineteen; potash, fifty-nine; soda, two; lime, two; sulphuric acid, six. Parsnip: phosphates, eighteen; potash, thirty-six; lime, eleven; salt, five. Carrot: phosphates, twelve; potash, thirty-six; soda, thirteen; sulphuric acid, six. Jerusalem Artichoke: phosphates, sixteen; potash, sixty-five.

In Class II. Sulphur, Lime and Soda Salts are predominant. This class consists of the more succulent plants, and includes the following: Cabbage: containing, in 100 parts of the ashes, phosphates, sixteen; potash, forty-eight; soda, four; lime, fifteen; sulphuric acid, eight. Turnip: phosphates, thirteen; potash, thirty-nine; soda, five; lime, ten; sulphuric acid, fourteen. Beet: phosphates, fourteen; potash, forty-nine; soda, nineteen; lime, six; sulphuric acid, five.

As a matter of course, Lentils and other kinds of pulse agree more or less with Peas and Beans in the predominance of phosphates and potash. So, again, all the Brassicas, whether Kales, Cauliflower, or whatever else, agree nearly with the Cabbage in the prominent presence of lime and sulphur; ingredients which fully account for the offensive odour of these vegetables when in a state of decay. Fruits as a rule are highly charged with alkalies, and are rarely deficient in phosphates; moreover, stone-fruits require lime, for they have to make bone as well as flesh when they produce a crop. As regards the alkalies, plants appear capable of substituting soda for potash under some circumstances, but it would not be prudent for the cultivator to assume that the cheaper alkali might take the place of the more costly one as a mineral agent, for Nature is stern and constant in her ways, and it can hardly be supposed that a plant in which potash normally predominates can attain to perfection in a soil deficient in potash, however well supplied it may be with soda. The cheaper alkali in combination as salt (chloride of sodium) may, however, be usually employed in aid of quick-growing green crops; and more or less with tap-roots and Brassicas. Salt, too, is very useful in a dry season by reason of its power of attracting and retaining moisture. As regards Potatoes, it is worthy of observation that they contain but a trace of silica, and yet they generally thrive on sand, and in many instances crops grown on sand are free from disease and of high quality, although the weight may not be great. The mechanical texture of the soil has much to do with this; and when that is aided by a supply of potash and phosphates, whether from farmyard manure or artificials, sandy soils become highly productive of Potatoes of the very finest quality. On the other hand, Potatoes also grow well on limestone and chalk, and yet there is but little lime in them. Here, again, mechanical texture explains the case in part, and it is further explained by the sufficiency of potash and phosphates, as also of magnesia, which enters in a special manner into the mineral constitution of this root.

Thus far we have not even mentioned nitrogen, or its common form of salts of ammonia; nor have we mentioned carbon, or its very familiar form of carbonic acid. These are important elements of plant growth; and they account for the efficacy of manures derived directly from the animal kingdom, as, for example, the droppings of animals, including guano, which consisted originally of the droppings of sea-birds. Some of the nitrogen in these substances, however, is of an evanescent character, and rapidly flies away in the form of carbonate of ammonia; hence, a heap of farmyard manure, left for several years, loses much of its value as manure, and guano should be kept in bulk as long as possible, and protected from the atmosphere, or its ammonia will largely disappear. One difficulty experienced by chemists and others in preparing artificial manures is that of ‘fixing’ the needful ammonia, so that it may be kept from being dissipated in the atmosphere, and at the same time be always in a state in which it can be appropriated by the plant. In all good manures, however, there is a certain proportion of it in combination, and in many instances the percentage of nitrogen is made the test of the value of a manure.

The importance of humus—the black earthy substance resulting from the decay of vegetation—in a soil is that it contains in an assimilable form many of the ingredients essential to plant life. Humus when it decomposes gives off carbonic acid, which breaks up the mineral substances in the soil and renders them available as plant food. When vegetable refuse is burned, the nitrogen—one of the costliest constituents—is dissipated and lost. But by burying the refuse the soil gets back a proportion of the organic nitrogen it surrendered and something over in the way of soluble phosphatic and potassic salts; and as this organic nitrogen assumes ultimately the form of nitric acid, it can be assimilated by the growing plant, to the great benefit of whatever crop may occupy the ground.

The practical conclusion is, that in the treatment of the soil a skilful gardener will endeavour to promote its fertility by affording the natural influences of rain, frost and sun full opportunity of liberating the constituents that are locked up in the staple; by restoring in the form of refuse as much as possible of what the soil has parted with in vegetation; and by the addition of such fertilising agents as are adapted to rectify the natural deficiencies of the soil. Thus, instead of following a process of exhaustion, the resources of the garden may be annually augmented.

ARTIFICIAL MANURES AND THEIR APPLICATION TO GARDEN CROPS

Plants, like animals, require food for their sustenance and development, and when this is administered in insufficient quantities, or unsuitable foods are supplied, they remain small, starved, and unhealthy.

The chemical elements composing the natural food of ordinary crops are ten in number, viz.—carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus, potassium, calcium, magnesium, and iron. These are obtained from the soil and air, and unless all of them are available plants will not grow. The absence of even one of them is as disastrous as the want of all, and a deficiency of one cannot be made up by an excess of another; for example, if the soil is deficient in potassium the crop suffers and cannot be improved by adding iron or magnesium. All the food-elements are found in adequate quantities in practically all soils and the surrounding air, except three—nitrogen, potassium, and phosphorus. These are often present in reduced amount, or in a state unsuited to plants; in such cases the deficiency must be made up before remunerative healthy crops can be grown, and it is with this express object that manures are added to the soil.

One of the best known substances employed in this way is farmyard manure, which is indirectly derived from plants and contains all the elements needed for the growth of crops. It is, however, of very variable composition and rarely, or never, contains these elements in the most suitable proportions, and its value can always be greatly improved by supplementing its action with one or other of the so-called artificial manures or fertilisers. Although it is strongly advisable to add farmyard manure or vegetable composts to the soil of all gardens now and again, in order to keep the texture of the soil in a satisfactory condition, excellent crops can be grown by the use of artificial fertilisers alone. To obtain the best results from these some experience is of course necessary, but the following details regarding the nature and application of the commoner and more useful kinds should prove a serviceable guide in the majority of cases.

Artificial manures may be divided into three classes:—

1. The Nitrogenous class, of which nitrate of soda and sulphate of ammonia are examples.

2. The Phosphatic class, such as superphosphate, basic slag, and steamed bone flour.

3. The Potash class, including kainit and sulphate of potash. The several examples of each class contain only one of the three important plant food-elements, and as a single element can only be of use when the others are present in the soil, it is generally advisable to apply one from each class, either separately or mixed, in order to insure that the crop is supplied with nitrogen, phosphates, and potash.

Nitrogenous manures specially stimulate the growth of the foliage, stems, and roots of plants, and are therefore of the greatest benefit to Carrots, Parsnips, Turnips, Beet, Celery, Asparagus, Rhubarb, all the Cabbage tribe, and leafy crops generally.

_Nitrate of soda_ supplies the single plant food-element, nitrogen, and the soda for all practical purposes may be disregarded. It dissolves very easily in water and is taken up immediately by growing plants, its effect being plainly seen a few days after application. As this artificial readily drains away from uncropped land it should only be administered to growing plants. It is best applied in spring and summer and in small quantities; for example, at the rate of one pound per square rod, repeated at intervals of two or three weeks, rather than in a single large dose. Nitrate of soda must not be mixed with superphosphate, but it may be added to basic slag and the potash manures.

_Sulphate of ammonia_ is another nitrogenous fertiliser, similar in its effects to nitrate of soda, but slower in action since its nitrogen must undergo a change into nitrate before it is available for plants. It is held by the soil, and can therefore be applied earlier in spring than nitrate of soda without fear of loss. The continued use of this manure, however, is liable to make the soil sour, and consequently it should only be employed on ground containing lime, or to which lime has been added. Never mix sulphate of ammonia with basic slag or with lime, but it may be mixed with superphosphate and the potash manures.

Phosphatic manures have the opposite effect to the nitrogenous fertilisers, checking rampant growth and encouraging the early formation of flowers, fruit, and seeds. They are comparatively inexpensive and should be liberally applied to all soils for all crops. _Superphosphate_ is an acid manure and best suited for use on soils containing lime. _Basic slag_ is a better material for ground deficient in lime, or where ‘club-root’ is prevalent. It is less soluble and therefore slower in action than superphosphate. Both these fertilisers should be dug into the soil some time before the crop is planted or seed sown—superphosphate at the rate of two to three pounds per square rod; basic slag in larger amount, five to six pounds per square rod. Superphosphate may also be employed as a top-dressing and worked into the surface around growing plants with the hoe. _Steamed bone meal_ or _flour_ is another useful phosphatic fertiliser, valuable on the lighter classes of soil.

Potash manures are of benefit to plants in all stages of growth. They are particularly valuable to Potatoes, leguminous crops, Carrots, Parsnips, Turnips, and Beet. Like the phosphatic manures they should be worked into the soil before seeds are sown or plants are put out. _Kainit_ is best applied in autumn, for it contains a considerable amount of common salt and magnesium compounds which are sometimes deleterious and best washed away in the drainage water during winter. It should be dug in at the rate of about three pounds per square rod. _Sulphate of potash_ is three or four times as rich in potash as kainit, and is correspondingly more expensive; apply in spring and summer, a little in advance of sowing or planting, at the rate of about one pound per square rod.

Lime.—- A word or two must be said about lime, which is a natural constituent of all soils. In many instances there is sufficient for the needs of most plants, but where lime is deficient in quantity it must be added before healthy crops can be raised. Old gardens to which dung has been freely applied annually require a liberal dressing of lime every few years, or the ground becomes sour and incapable of growing good crops of any kind. To insure the proper action of whatever manures are used and to secure healthy crops, an application of slaked quicklime, at the rate of fourteen to twenty pounds per square rod, is strongly recommended. As a remedy against ‘clubbing’ or ‘finger-and-toe’ disease of the Cabbage tribe of plants it is indispensable; it also neutralises the baneful acidity of the land, and opens up stiff soils, making them more easily tilled, more readily penetrated by the air, and warmer by the better drainage of water through them.

The following suggestions for the manuring of the different crops mentioned will be found effective. It is, however, not intended that they should be slavishly followed, for useful substitutions may be made in the formulæ given, if the nature of the various fertilisers is understood and an intelligent grasp is obtained of the principles of manuring enunciated in this and the preceding chapter.

In place of nitrate of soda, a similar quantity of sulphate of ammonia may be used.

Instead of superphosphate, the following may be advantageously employed: phosphatic guano, or mixtures of basic slag and superphosphate, or bone meal and superphosphate; or basic slag may be applied alone on land deficient in lime.

Four pounds of kainit may also take the place of one pound of sulphate of potash in the suggested mixtures mentioned below.

Where dung is recommended, twenty to twenty-five loads per acre is meant; larger quantities are frequently applied, but these are uneconomical and much less efficient than more moderate amounts supplemented with artificial fertilisers.

All the manures should be worked into the soil before sowing or planting out, except the nitrate of soda, which is best applied separately to the growing plants, preferably in small doses at intervals of two to four weeks.

_In all cases the quantities of artificials named are intended for use on one square rod or pole of ground._

PEAS AND BEANS.—These leguminous plants are able to obtain all the nitrogen they need from the air. They should, however, be amply supplied with potash and phosphates, a good dressing being:—

2-3/4 to 3-1/2 lb. superphosphate 3/4 lb. sulphate of potash

DWARF BEANS are sometimes benefited by the addition of 1/2-lb. to 1 lb. of nitrate of soda.

ASPARAGUS.

A dressing of dung 2 lb. nitrate of soda 3-1/2 to 4 lb. superphosphate 3 lb kainit

The kainit contains a considerable amount of salt, which is of value to this crop.

BEET.—For a fine crop a moderate amount of well-decayed dung applied in autumn is almost essential, as well as 3 to 4 lb. of superphosphate per square rod in spring. On land previously dressed with dung for a former crop, the following may be used, especially on the lighter class of soils:—

1-1/2 lb. nitrate of soda when the plants are well up, and a similar amount a fortnight after singling 4 to 5 lb. superphosphate 4 lb. kainit

BROCCOLI AND CAULIFLOWER.

_With dung_. 2 to 3 lb. nitrate of soda 2 to 3 lb. superphosphate 3/4 lb. sulphate of potash

_Without dung_. 4 to 5 lb. nitrate of soda 4 to 5 lb. superphosphate 3/4 lb. sulphate of potash

CABBAGE, KALE, AND BRUSSELS SPROUTS.—These Brassicas require considerable quantities of nitrogen and phosphates. For spring Cabbage planted in autumn, land well dunged for the previous crop gives good results with the addition of the artificials mentioned below: for the autumn crop, dung should be applied before planting out in the early part of the year.

_With dung_. 2 to 3 lb. nitrate of soda 4 to 5 lb. superphosphate 3/4 lb. sulphate of potash

_Without dung._ 4 lb. nitrate of soda 5 to 6 lb. superphosphat 3/4 lb. sulphate of potash

CARROT AND PARSNIP.—A good dressing of dung applied to the previous crop is a valuable preparation where Carrots and Parsnips are to be grown. In addition, one of the following mixtures should be used:—

(1) 3/4 lb. nitrate of soda 3 to 4 lb. superphosphate 3/4 lb. sulphate of potash

(2)

3/4 lb. nitrate of soda 2 lb. superphosphate 1 to 2 lb. basic slag 3 lb. kainit

CELERY requires the use of dung more than almost any other crop, and it is little affected by artificial manures, except phosphates, which may be given in the form of superphosphate at the rate of 2-1/2 to 3-1/2 lb per square rod.

LETTUCE.

_With dung_. 3 to 4 lb. superphosphate 1/2 to 1 lb. nitrate of soda

_Without dung._ 3 to 4 lb. superphosphate 1 to 1-1/2 lb. nitrate of soda 1 lb. sulphate of potash

ONIONS never succeed without an ample supply of potash. This crop should therefore have farmyard dung, or the special potash fertilisers in adequate quantity.

_With dung._ 3/4 lb. nitrate of soda 4 to 5 lb. superphosphate 3/4 lb. sulphate of potash

_Without dung._ 1-1/2 to 2-1/2 lb. nitrate of soda 5 lb. superphosphate 1 lb. sulphate of potash

LEEKS require the same fertilisers as Onions, but will need little or no nitrate if good dung is used.

POTATO.—For good yield, high quality, and freedom from disease, Potatoes are dependent upon a good supply of potash. They do best when supplied with a moderate amount of farmyard manure, supplemented by suitable artificials, but can be grown on some soils with artificials alone.

_With dung_. 3/4 lb. sulphate of ammonia 3 lb. superphosphate 3/4 lb. sulphate of potash

_Without dung_. 1-1/2 lb. sulphate of ammonia 3-1/2 lb. superphosphate 1 to 1-1/2 lb. sulphate of potash

Instead of superphosphate, a mixture of this fertiliser with an equal amount of bone meal or basic slag may be used, and either 4 lb. of kainit and 1 lb. of muriate of potash instead of 1 lb. of sulphate of potash.

RHUBARB.—An annual dressing of dung is beneficial, together with 6 lb. of basic slag, 1 lb. of sulphate of potash, and 4 lb. of nitrate of soda, half the nitrate being applied when growth commences and the remainder a fortnight later.

SPINACH.

_With dung_. 3 to 4 lb. superphosphate 2 to 3 lb. nitrate of soda

_Without dung_ 4 to 5 lb. superphosphate 1 lb. sulphate of potash 3 to 4 lb. nitrate of soda

TOMATOES need large supplies of potash and phosphates to induce stocky growth and abundance of flowers and fruit. Nitrogenous manures should be withheld until the flowering stage, for they stimulate the production of rank succulent stems and leaves which are specially liable to attacks of fungus pests. After the fruit is set the application of small doses of nitrate of soda, or sulphate of ammonia, as advised below, greatly assists the swelling of the crop. The following mixtures worked into the soil will be found beneficial for Tomatoes:—

5 to 6 lb. superphosphate 7 to 8 lb. basic slag 1 lb. sulphate of potash _or_ 1 lb. sulphate of potash

Nitrate of soda, or sulphate of ammonia, at the rate of 1-1/2 to 2 lb. per square rod, may be given with advantage as soon as the fruit is set.

TURNIP AND SWEDE.—For the development of fine roots a liberal supply of phosphates is essential.

_With dung_. 1 lb. nitrate of soda 3 to 4 lb. superphosphate 3/4 lb. sulphate of potash

_Without dung_ 2 lb. nitrate of soda 4 to 5 lb. superphosphate 1 lb. sulphate of potash

THE CULTURE OF FLOWERS FROM SEEDS