Choosing and Using Fertilizers

Basic Slag. A slow-acting phosphatic fertilizer which also supplies lime. It is a steel-industry by-product and must be ground by machinery; the coarser the grinding the slower

its action. Slag may remain in the soil for several years. Quality varies, and analysis may show anything from 8 to 22% phosphoric acid. Also the solubility, and consequently the availability, of the phosphoric acid varies. This is quoted on basis of solubility in citric acid. Over 80 % soluble is good; below 40% poor and exceptionally slow acting. Most useful for autumn or winter application at rates from 4 to 8 oz. per square yard.

Blood. Contains nitrogen and is a useful manure. Fresh blood may be dug freely into vacant ground but is messy and unpleasant to handle. Usually it is dried. This can be done at home by adding 1 lb. of fresh slaked lime to each gallon of blood, stirring, pouring into a shallow box and covering with a thin layer of lime. Leave until dry, then apply at 4 oz. per square yard. Commercial dried blood is a fine dry powder containing about 7-14% nitrogen. This can be applied at rates up to 2 oz. per square yard or stirred into water (it is not usually fully soluble) at rates to 1 oz. per gallon. Most serviceable for spring and early summer use and for plants in full growth or bearing.

Bonemeal. An invaluable source of phosphates. Bone-meal is slow acting but this will depend on the grinding. The finer this is the more rapidly will the fertilizer be available. Analysis shows from 1 to 5% nitrogen (the high figure for raw bones containing gelatine not present in prepared bonemeal or bone flour), phosphoric acid 20 to 25%. Rates of application up to 4 oz. per square yard, or 4 oz. per bushel of potting soil. Most useful for autumn and winter application and in potting composts.

Calcium Cyanamide. A quick-acting nitrogenous fertilizer which also supplies lime. It is dusty and rather difficult to apply evenly. Has a caustic effect on roots and leaves and should be kept out of direct touch with them. May be used as a weed-killer and fertilizer combined. Rate of application 1-2 oz. per square yard. Use in late winter or spring. Analysis: 206% nitrogen, about 22% free lime. May be used as a rotting agent in compost heaps.

Coal Ashes. Of no value as a fertilizer. Sharp boiler ashes may be used to lighten clay soils.

Fish Guano, The dried refuse from factories engaged in the smoking or canning of fish. It contains nitrogen, phosphorus and other plant foods and may be used like guano. Average analysis: nitrogen 6-10%, phosphoric acid 4-9%, potash %. Fresh fish refuse may also be dug into the soil and

forms a good substitute for farmyard or stable manure. Prepared fish manure usually contains other chemicals to make it a better-balanced food and should be used according to manufacturers’ instructions.

Flue Dust. Usually of no value, but some samples contain potash. Ask for potash analysis before buying.

Guano. Strictly this name belongs only to the excreta of sea birds deposited on the sea coast of Peru and other tropical but almost rainless districts. Such guano is a rich, complete manure, chiefly of use as a powerful stimulant during the growing season. It should be used at the rate of 2 to 3 oz. per square yard or about 1 oz. per gallon of water. Analysis varies greatly from: nitrogen 2-12%, phosphoric acid 10-20%, potash 2-4%. The term ‘guano’ is now loosely applied to many compound chemical fertilizers.

Hoof and Horn Meal. A steady-acting manure which is of great value in the garden and especially with potting composts. With these it may be mixed at the rate of 11 oz. per bushel. Outdoors it may be employed at rates up to’ 2 oz. per square yard. Average analysis: 12-14% nitrogen, 1-3% phosphoric acid.

Kainit. A crude form of potash in which muriate of potash is combined with common salt and other chemicals. Kainit is best applied in autumn or winter at rates up to 3 oz.

per square yard. Average analysis: potash 14%, common salt 50-60%, magnesium sulphate 20%.

Leather Dust. Contains small quantities of nitrogen, but this becomes available very slowly and leather dust is principally of value for adding bulk to more concentrated fertilizers and thus making it easier to distribute them. Rate of application up to 1 lb. per square yard; at any time.

Lime. Strictly speaking, lime is calcium oxide, but the term is loosely applied in gardens to several other compounds of calcium. Though required by plants as food, calcium itself is almost invariably present in the soil in sufficient quantity for this purpose. Calcium oxide, calcium hydroxide, calcium carbonate and (less commonly) calcium sulphate are added as soil sweeteners, to liberate other chemicals and to improve the texture of heavy ground. For these purposes all forms of lime, including chalk, are identical except that some act more rapidly and others have better moisture-holding qualities.

HYDRATED LIME (air-slaked lime) is the quickest-acting form which can be used with safety around plants. A powder for use at rates up to 1 lb. per square yard.

CHALK (calcium carbonate) is slower in action, though this depends very much upon the fineness of grinding. Is especially suitable for light soil, as it holds moisture. Can be used at rates up to 2 lb. per square yard.

GROUND LIMESTONE is another form of calcium carbonate. It is even slower acting, but again much depends on fineness. Can be used in the same way as chalk.

QUICKLIME (calcium oxide) is quick acting but caustic and only suitable for use on vacant land at rates up to 1 lb. per square yard. It kills insects, etc., in the soil.

GYPSUM (calcium sulphate) is commonly used for improving soil structure and particularly for heavy clay soils. On heavy soils a dressing of 8 oz. per square yard can be given.

GAS LIME contains sulphurous impurities which are

poisonous to plants and many insects. Can only be used on vacant land and is then valuable both as a source of lime and as a soil fumigant for destroying such pests as wireworms, slugs, etc.

MAGNESIAN LIMESTONE is a special form of limestone which contains magnesium as well as calcium carbonate. It may be used with advantage on all soils lacking in magnesium.

FERTILIZERS which contain free lime and therefore add it to the soil are nitrate of lime, Nitro-chalk, calcium cyanamide, and basic slag.

Superphosphate of lime contains no free lime and cannot be employed in place of lime.

METHOD OF TESTING SOIL FOR LIME. Take a typical sample of soil, break up finely and half fill a tumbler with it. Pour in dilute hydrochloric acid. If there is much effervescence, free lime is present; if there is little or no effervescence, there is little or no free lime. This is a very rough and ready method of testing, however, as ‘free lime’ is not essential to the health of either plants or soil. What is important is ‘available lime,’ i.e. lime in a particular physical association with the finest soil particles (colloids). This ‘available lime,’ is not shown by the acid test. A truer estimate can be obtained by means of a chemical ‘soil indicator’ giving a pH reading. If this shows pH 7.0 the soil is neutral. If the figure is higher than 7.0 the soil is alkaline, if below this figure it is acid. As a rule lime will be required only when the figure drops below 6.5 and even then not by any means for all plants. Rhododendrons and heathers thrive in soils as acid as pH 5.0.

Meat Meal. Pure meat refuse is mainly a nitrogenous manure, but meat meal or meat guano usually contains ground bones as well which increases its phosphatic content. Use in the same way as fish guano or refuse.

Mineral Phosphates. A source of slowly available phosphoric acid comparable with basic slag as a phosphatic

fertilizer. Most useful for permanent crops and pastures. Rate of application 3-4 oz. per square yard. Best used in autumn or winter. Average analysis from 25 to 35% phosphoric acid. The finer the mineral is ground the better.

Muriate of Potash.. A relatively pure form of potash which must be used with caution, as it is injurious to some tender roots if brought directly into contact with them. Muriate of potash is frequently used in compound fertilizers and is readily soluble. Rate of application 1-1 oz. per square yard. Tends to make potatoes more waxy in texture. Best applied in autumn or winter. Analysis: potash 40-60%, common salt 13-18%. (Correctly known as potassium chloride.)

Nitrate of Potash. This is also known as saltpetre. It contains both nitrogen and potassium in readily assimilable form and is of great value as a liquid manure for pot plants if dissolved in water at the rate of oz. per gallon. Is too expensive for outdoor use. Analysis: nitrogen 12-14%, potash 44-46%. Do not confuse with potash nitrate.

Nitrate of Soda. A very soluble salt rich in nitrogen. Much used as a top dressing in summer, either alone or in combination with other quick-acting fertilizers. Has a caustic effect upon foliage and may do damage if applied carelessly. Nitrate of soda must not be mixed with superphosphate of lime. It tends to make clay soils more sticky. Rate of application

oz. per square yard, 1-1 oz. per gallon. Analysis: 16% nitrogen.

Nitrate, of Lime. Like Nitro-chalk, a quick-acting, granular nitrogenous fertilizer for general use in spring and early summer. Rate of application 1 oz. per square yard. May be used as a rotting agent on compost heaps. Analysis: nitrogen 15—l6%.

Nitro-chalk. A quick-acting proprietary fertilizer in granular form which supplies the soil with nitrogen and lime. Particularly valuable for acid and lime-free soils. Rate of application 1 oz. per square yard. Most suitable for spring or early summer application. May be used as a rotting agent on compost heaps. Analysis: nitrogen 151%, carbonate of lime 48%.

Phosphate of Potash. Contains both phosphorus and potassium. Is very soluble and most serviceable as a liquid stimulant for pot plants in full growth. Use at oz. per gallon. Too expensive for use outdoors. Analysis of commercial phosphate of potash is phosphoric acid 51%, potash 35%.

Potash Nitrate. Often sold as Chilean potash nitrate and not to be confused with nitrate of potash, a quite different chemical. This is a quick-acting fertilizer supplying nitrogen and potash. Rate of application oz. per square yard. Most

suitable for spring or early summer application. Average analysis: nitrogen 15%, potash 10%, but some samples contain a higher proportion of potash and are correspondingly more valuable.

Potash Salts. A general name given to various natural deposits containing muriate of potash in combination with other salts, such as common salt and magnesium sulphate. Kainit is a potash salt. Others, not usually specifically named, contain higher percentages of potash. Should be bought on potash analysis, e.g. 30% potash salts are worth half again as much as 20% potash salts. Rate of application 1-2 oz. per square yard. They are best applied in autumn or winter.

Rape Meal. A by-product from oil mills. It contains nitrogen and also adds humus to the soil. Is valuable as a base for compound fertilizers containing strong chemicals such as sulphate of ammonia, superphosphate of lime, and muriate of potash. It aids the even distribution of the more concentrated chemicals. Rate of application up to 4 oz. per square yard. Average analysis: 5-6% nitrogen.

Salt (sodium chloride). Used more frequently as a weedkiller than as a fertilizer, but is a source of sodium and helps to liberate potash already in the soil. Rate of application 1 oz. per square yard. Best used in winter or early spring. Is sometimes given to asparagus and seakale beds.

Sequestrols. Some necessary elements rapidly become insoluble (and therefore unavailable as plant food) through chemical interaction in the soil. This is likely to occur with iron and manganese on alkaline soils, with copper on acid sandy or peaty soils and with zinc on sandy neutral or alkaline soils. Ordinary salts of these chemicals such as sulphate of iron and sulphate of manganese may then prove ineffective and instead special organic compounds known as sequestrols or chelates must be used. In these the necessary element is held for a considerable time immune from chemical reaction, yet available to plants. Sequestrols or chelates are sold as manufactured products sometimes individually, sometimes combined with other plant foods. Since they vary in formulation label instructions must be followed.

Soot. A good sample may contain as much as 6% nitrogen in the form of sulphate of ammonia. Fresh soot is rather caustic and may be used as a soil fumigant to destroy insects and slugs. For use as a fertilizer it is best stored in the dry for three or four months. If exposed to rain or mixed with lime it quickly loses its value, though lime makes it yet more effective as a soil fumigant. Soot also enables soil to absorb sun heat more readily. Rate of application up to 6 oz. per square yard. May be used at any time.

Steamed Bone Flour. Virtually identical from the garden standpoint with fine bonemeal except that all gelatine has been extracted so the flour is very dry, and mixed with other fertilizers it prevents them caking.

Sulphate of Ammonia. A nitrogenous fertilizer used in a similar manner to nitrate of soda. On the whole a safer chemical to use, as it is not quite so quick acting or caustic. Tends to increase the acidity of acid soils. Must not be mixed with lime but may be mixed with superphosphate of lime, sulphate of potash, and muriate of potash. Rate of application -1-1 oz. per square yard. Best used in spring or early summer. Analysis: 20.6% nitrogen.

Sulphate of Iron. If iron is lacking in the soil it may be applied in this form. Dressings at the rate of up to 1 oz. per square yard may be made in spring. Is also used as a fungicide to kill toadstools, etc., on lawns and root-rot fungi at rates up to 4 oz. per gallon of water.

Sulphate of Magnesium. If magnesium is lacking, this is the form in which it is usually supplied. The common salt as purchased is Epsom salt and contains water of crystallization which reduces its concentration to 10% magnesium. The rate of application for this commercial product is 1 oz. per square yard or I-1 oz. per gallon of water.

Sulphate of Potash. The best form of potash for general use. It is non-caustic and reasonably quick acting. May be used at any time of the year. Rate of application 4-1 oz. per square yard. Analysis: 48% potash. Frequently increases disease resistance.

Superphosphate of Lime. The best form in which to apply phosphates where a quick result is desired. Contains no free lime and will not affect acidity. Rate of application 1-3 oz. per square yard. Most suitable for application in spring or early summer, but is apt to burn delicate foliage or flowers. Analysis: 18% phosphoric acid.

Wood Ashes. A useful but variable source of potash. The amount present will depend upon the type and age of the wood burnt and the method of storage. Much potash may be washed away if wood ashes are left in the open. A good sample will contain 15% potash, a poor one as little as 4%. Apply up to 8 oz. per square yard, at any time of the year.

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