MANURES AND FERTILISERS

These terms are to some extent interchangeable, although gardeners often refer to organic manures, I.e. natural substances of vegetable or animal origin like horse and cow droppings, as’manure’, while by contrast they term inorganic, synthesised materials like sulphate of ammonia and ‘Nitro-Chalk’, which contain plant foods in concentrated form but do not in themselves increase the humus content of the soil, as ‘artificials’. A better term would be ‘mineral fertilisers’. Such compounds are often used to accelerate growth, although some are relatively slow-acting.

Considerable misunderstanding exists regarding the relative virtues of manures and fertilisers. It may be helpful to clarify the picture which has often been distorted by the opponents of the so-called artificials. In the first place, the organic material in the soil comprising humus is ‘in the nature of a practical convenience rather than a sheer necessity’ (Sir E.J. Salisbury). Plants can be grown in a nutrient solution, entirely devoid of organic materials . Dislike of chemicals is often based on the belief that before their use became widespread insect pests and fungus diseases were unknown. However, pests and diseases were known to farmers and even gardeners many centuries before inorganic fertilisers were used. Note that whether, say, nitrogen is applied as sulphate of ammonia crystals and watered in, or as farmyard manure, it is still changed by the soil micro-organisms into similar compounds, I.e. nutrient ions, taken up in solution by the plant.

Organic manures and fertilisers should be regarded as complementary. Fertilisers only tend to exhaust the soil if used to excess without the corresponding addition of compost, manure etc. With proper usage the resulting heavier crops mean that the organic matter in the soil is definitely increased as greater quantities of roots are left as residues.

Soil erosion in the U. S. A. was caused by bad farming, not fertilisers as such.

Here are some notes on the main plant foods, followed by details of the various forms in which they can be applied.

Note that by a complete or compound fertiliser is usually meant one containing the three main elements, nitrogen, phosphorus and potash, which are often condensed on labels etc. to N, P2 ½ 5 an< K20 respectively, magnesium being expressed as MgO.

Nitrogen:

The main element concerned with growth and derived in Nature from decaying vegetable matter. If the soil is well supplied with this element, growth is vigorous and foliage dark green. Where nitrogen is lacking, growth is stunted, leaves being pale and yellowish-green. Used to excess, nitrogen produces soft, sappy growth which is often more susceptible to attacks by aphids. Ripening can also be delayed. Nitrogen is to some extent leached or washed out of the soil, especially in areas of high rainfall and on hillside land. This deficiency can be made good by the use of farmyard manure or inorganics, like sulphate of ammonia and ‘Nitro-Chalk’.

Farmers use nitrogenous fertilisers on grassland to extend the grazing season, to produce an ‘early bite’ for cattle several weeks before the grass would be growing normally, to increase the protein content of the hay crop and so on. They also top-dress autumn-sown cereals in spring. For example, 2 1/2 cwt. ‘Nitro-Chalk’ gives an extra 5 cwt. grain per acre. Gardeners can apply the same material to cabbages, cauliflowers, etc., when the plants are about three-quarters grown.

Phosphorus:

This element (often referred to as phosphates) is essential for root formation, also the ripening of fruits and seeds. Effects on growth and foliage are similar to nitrogen deficiency but foliage can also turn bluish-green with purple or bronze markings.

Potash:

The precise functions of this element are still under investigation. Potash is often in short supply on light, sandy soils and browning or scorching of foliage on apples, gooseberries and red currants is a sign of deficiency. Colouring of fruits and flower is said to be improved by adding potash and some claim that it helps to make plants (especially roses) more resistant to disease. These claims have yet to be confirmed scientifically. It seems, however, that potash does play a part in stimulating the production of sugar and starch.

Magnesium:

This element is a constituent of the chlorophyll or green colouring matter in the leaves and may be a carrier of phosphorus. Magnesium deficiency usually shows up first in the older leaves which turn yellow (chlorotic) or develop red, purple and yellow tints. Defoliation can also occur. For example, with tomatoes, the older leaves turn yellow, hang on the plant and die, the trouble progressing upwards.

Magnesium is fairly easily leached out of the soil, especially on light, sandy land during wet spells. It is now included as a constituent of some proprietary fertilisers.

Notes on Specific Fertilisers and Manures:

The following selection covers some of the better-known materials which are readily available to amateurs.

Basic Slag. A relatively inexpensive source of phosphorus. It is produced as a waste product in steel manufacture. Pig iron which contains phosphorus is smelted with limestone. This combines with the phosphorus and other impurities, the iron turns to steel and a slag is left, known as basic slag. It contains 8% to 16% P205, 40 — 50% lime plus certain minerals, such as iron, magnesium etc. It is insoluble in water and somewhat slow-acting. It is particularly useful on heavy and acid soils and helps to break up intractable clays, thereby improving texture. Basic slag remains in the soil until taken up by the plant — it is not washed out or leached from the land. Basic slag is equally valuable on light soils if supplemented by potash — in Europe this is common practice. 4—8 oz. per sq. yd is the application rate for most garden crops. Do not use on lawns as it encourages clover and do not mix with sulphate of ammonia or other manures containing ammonia.

Bonemeal. Another phosphatic fertiliser produced by grinding raw and dried bones and very popular with gardeners as it is difficult to misuse. Releases its phosphates (usually 15—32%) slowly over a long period. Also contains small quantities of nitrogen. Application rates 4—6 oz. per sq. yd.

Dried Blood. Contains about 12% nitrogen and is quick acting. Dearer than most fertilisers because it is dried and not ground, the former being the more costly process. Use at ½ — 1 oz. per gallon of water. Hoof and Horn Meal. Another fairly expensive fertiliser which supplies the nitrogen in the John Innes Composts. Also contains 12 — 14% nitrogen but is not quick acting, the nitrogen being released gradually over several months. Use at 2 oz. per sq. yd.

Nitrate of Potash. There are two types, both quick acting. Nitrate of potash (saltpetre) contains 13—14% nitrogen and 45% potash. (Chilean) potash nitrate contains 15% nitrogen and about 14% potash. It is a natural mixture of nitrate of potash and nitrate of soda. Use both materials at ½ oz- Per gallon of water.

Nitrate of Soda. A very quick acting nitrogenous fertiliser — usually 15 ½ —16% nitrogen. Inclined to scorch foliage and makes heavy soils more sticky. Store in a very dry place as it rapidly attracts any available moisture, even from the atmosphere. Use at ½ oz. per gallon of water.

Nitro-ChaW. A proprietary fertiliser in granular form making for convenient handling. Contains 15% ammonium nitrate and 48% carbonate of lime. Quick acting and gives especially good results on acid and heavy soils. Use according to manufacturer’s directions. Sulphate of Ammonia. Another very quick acting fertiliser which contains 20.8% nitrogen as ammonia. It gives maximum results on soils not deficient in lime. It does not damage the texture of heavy, clay soils as may nitrate of soda nor does it absorb moisture too readily. Nevertheless, like all fertilisers, it should be stored in a dry place. Sulphate of ammonia is clean and easy to handle and on the basis of unit value must be termed the cheapest form of nitrogenous fertiliser. It may be applied as a liquid fertiliser using ½ oz- Per gallon of water. It is an excellent fertiliser for lawns and vegetables, especially brassicas and lettuces. Sulphate of ammonia should be used more widely on apples and pears by amateurs. February or March applications are strongly recommended. Note that cooking apples can take more nitrogen than dessert varieties. Among the latter, Cox’s Orange Pippin always responds to generous manuring. See APPLE — Choice of Varieties:, for an account of the idiosyncrasies of this well-known variety!

Do not mix with alkaline materials such as lime, basic slag or wood ashes. Note that sulphate of ammonia can be mixed with superphosphate of lime and sulphate of potash to form a complete or compound fertiliser. Sulphate of Iron (Green Vitriol or Copperas). Where iron is deficient plants are unable to develop chlorophyll or green colouring matter and the leaves turn yellow or white. Spraying the foliage with a solution of sulphate of iron (about I oz. per gallon of water) is helpful. Sulphate of Magnesium (Epsom Salts). Where magnesium is lacking this material may be applied as a liquid, say, ½ oz. per gallon of water. Sulphate of Potash. This usually contains 48% potash, is fairly quick acting, and may be used at 2—3 oz. per sq. yd. Muriate of potash (potassium chloride) is slower acting, contains 50 — 60% potash but the chlorine content may sometimes injure the roots of certain plants, e.g. black currants and roses. Sulphate of potash is a safe material for the gardener.

Superphosphate of Lime. A quick acting phosphatic fertilizer containing 16— 18% phosphoric acid. Fairly soluble in water. Best used in spring or early summer.

Wood Ashes. A useful source of potash, although the potash content is relatively low, varying from as low as 2 % to 14%, depending on the type and age of the wood. Fruit and rose tree prunings, also hedge clippings, should always be burnt. Store the ashes under cover immediately they are cold as the potash is rapidly washed out by atmospheric moisture and rain. Heavy dressings can easily cake the surface of the soil but it is difficult to give precise rates of application as the potash content of each sample is so variable.

Seaweed. Among other materials employed as fertilisers, seaweed has been widely used in recent years. It rots down quickly when wet but dried seaweed is easier to apply. An average wet sample contains about 0.5% nitrogen, 0.1% phosphoric acid and 1% potash. Heavy dressings are needed if seaweed is applied in the wet state, say, 1 cwt. to 8sq. yds., but it may be dug in when dry at about half this rate. Proprietary fertilisers containing seaweed are available and should be used according to the manufacturer’s directions.

Salt (a combination of sodium and chlorine) was often used by old time gardeners for asparagus, carnations, etc. However, sodium is not an essential element in plant growth and it may have a deleterious effect on the texture of the soil. On the farm, sugar beet and mangolds seem to respond to applications of salt and in the garden it is still worth while top-dressing asparagus beds in early spring at about I oz. per sq. yd. Fish manure is a complete fertiliser containing dried fish waste plus additional plant foods. Use according to manufacturer’s instructions. Hop manure is a proprietary product containing dried hops supplemented by other plant foods to make a dual-purpose product which acts as a complete fertiliser and a potential source of humus. Application rates vary according to the particular product. Hop manure may also be used as a mulch or dug into the soil when preparing ground for planting roses, fruit trees etc. Spent hops obtained direct from the brewery contain little or no plant foods but are an excellent source of humus. They should be allowed to stand for several months and dug into the ground, allowing a barrowload to every 10 sq. yds.

Leaf Mould and Peat have very little manurial value but are important for their humus-forming properties. They can also be used for mulching.

Compost is derived from vegetable refuse, including annual weeds, dead flower stems etc. This has high manurial value, helps to provide humus and is again valuable for mulching.

Sewage sludge is another source of humus and is probably most useful on light, sandy soils. It contains limited quantities of nitrogen, phosphorus and potash. Dried sewage can be bought quite cheaply from some local authorities.

Soot should not be applied when fresh, by reason of its caustic properties. If allowed to stand under cover for about 3 months, it can be used as a fertiliser at 6 oz. per sq. yd. It contains a small amount of nitrogen. Soot improves the texture of clay soils and darkens light soils so that they absorb heat more quickly and thereby warm up a little earlier, especially in spring. It can also be used to make ‘soot water’ for feeding plants, instead of applying dry. Soot has a deterrent effect on slugs. Farmyard manure (e.g. cow, pig, horse) is the best known form of organic manure and as already emphasised, greatly improves the physical condition of the soil, opening up heavy land and making lighter land more drought-resistant. It is also a first-rate source of humus, and supplies small amounts of nitrogen, phosphorus and potash. Cow and pig manure being cold and wet are best applied to light land, whereas horse or stable manure, which heats up rapidly, should be kept for heavy soils. Note that these are counsels of perfection, as nowadays gardeners are often compelled to make use of any manure which they can obtain, irrespective of soil conditions. On light and free working soil it is advisable to apply manure in the spring. On heavy and sticky soils, it is preferable to apply ‘strawy’ manure during the autumn digging. When this is done the action of the weather makes the surface of the soil friable and suitable for seed sowing the following spring, improves the texture, increases the warmth and renders the land much easier to work.

Only well-rotted manure should be used. Fresh material is usually too hot, unless the ground can be left for some time before planting. It should be kept heaped and covered with about 6 in. of soil, under a roof. If left exposed to rain and air it will lose bulk and plant foods. Poultry manure can be bought in dried form. Those with hens, ducks, geese etc. can use the droppings for digging in to vacant ground at any time of the year. Most samples are too strong to use on growing crops (they are richer than farmyard manure) but may be added to the compost heap. Fattening fowls give richer manure than laying hens and young chickens.

Note that most plants (potatoes excepted) should not be planted with their roots in or just above manure, otherwise they may be burnt. Always mix the manure with the soil and do not place in separate layers. See also LIQUID MANURE.

Application. Endeavour to distribute manures and fertilisers as evenly as possibly — granular fertilisers are usually far easier to distribute by hand (and mechanical means) as they are not blown away by the wind. Never apply manurers or fertilisers of any kind with lime .

Fertilisers should not be applied during drought unless the ground can be watered regularly. Most powder fertilisers are best dissolved in water and applied by watering-can as results are quicker than if the roots have to wait to take up the fertiliser until rain has fallen. Liquid fertilisers which merely require to be diluted with water are well worth trying. The old warning never to sow seed and fertiliser in the same drill as this might impair seed germination is probably only a half-truth as nowadays farmers utilise a combine drill to send fertiliser and seed down the same spout. Fertiliser placement is being actively investigated as it seems that with certain shallow-rooted crops like peas and beans placing the fertiliser about 2 in. to the side and I in. below the seeds, may prove more effective than the convential broadcast application. Fertiliser applications can be made 2 to 3 days before sowing seed, cither in solution or lightly worked into the soil and watered in. Little and often is a better rule for feeding than occasional large ‘doses’ (the opposite of the rule for watering). For fruit trees, shrubs, roses and any plants with spreading roots, it is desirable to distribute fertilisers in a broad ring, extending a little way beyond the area covered by the spread of the branches, as the feeding roots usually extend thus far.

Foliage feeding as distinct from the familiar method of application to the roots has attracted considerable attention in this country. Big claims have been made for this new technique, especially for foliage feeding with antibiotics. Experiments are still in progress and it would be premature to issue specific recommendations until more data on controlled scientific experiments is available. It is, of course, well known that sulphate of iron, magnesium sulphate etc., may be applied in this way to fruit trees and roses but authoritative data on complete fertilisers used as foliage sprays is still awaited.

Sequestrene salts applied to the soil represent a comparatively new development. They have been used to control chlorosis on hydrangeas, primulas, roses, salvias, etc. Similar compounds to cure other mineral deficiencies are available.

Another interesting development is a combined insecticide and fertiliser. For example, aldrin which tackles soil pests such as leather jackets, wireworm etc., is combined with a special vegetable fertiliser. Note that specially formulated fertilisers to cover particular crops are obtainable. It is always worth while applying a compound fertiliser before sowing or planting most vegetables and again when they are in active growth. Wherever there is a piece of the plot or garden which is clear by the end of August or early September and is not required for another crop before the end of the year, it is a good plan to sow some mustard broadcast after the ground has been lightly pricked over. This should be dug in just before it begins to show flower, and before severe frost sets in; it will help to keep up the stock of humus in the soil. Lupins, from surplus seed, do the same. See GREEN MANURING. Closely allied to manuring is the changing of positions for vegetable crops. Vegetables should be arranged in groups, and one crop, or group of crops, should be followed by another making somewhat different demands on the soil, and leaving the soil in best condition for the next crop. This will keep the soil in a better balanced condition, improve the quantity and quality of the crop. See ROTATION; also CROPPING PLAN.

Storage of Fertilisers:

All fertilisers should be stored in a completely dry, well-ventilated and weatherproof building to protect against rain, condensation moisture and dampness from the ground. Corrugated iron roofs and walls tend to cause ‘sweating’. It is advisable to separate different types of fertiliser. Thus fertilisers which absorb moisture readily like ‘Nitro-Chalk’ or nitrate of soda, should be kept away from bonemeal or sulphate of potash.

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