FERTILIZERS: INCLUDING MANURES
Under garden cultivation soils lose their available plant foods more quickly than they can be replaced by Nature. To make good such losses and to renew and enhance the fertility of a soil, it is necessary to manure and fertilize.
A manure may be defined as a bulky material
of organic and natural origin which supplies humus-forming substance and plant foods. Strictly, manures are fertilizers, but the term fertilizer is of ten used in a more restricted sense to apply only to more concentrated sources of plant foods, which provide little or no humus, and may be of organic or inorganic nature. Both manures and fertilizers are desirable to bring soils into a state of high fertility. To get the best results, they should be chosen according to their nature and content and with some consideration of the soil and plants they are to feed.
These consist largely of animal excreta, usually together with plant remains, in one form or another. They are valuable sources of humus, which is so essential for the maintenance of soil structure; of microorganisms beneficial to biochemical soil reactions; and of various plant foods, chiefly nitrogen, phosphorus and potash. Their precise content of plant nutrients varies according to the age and feeding of the animals and subsequent treatment of the manure.
Cow Manure. Average analysis: 0.4 per cent nitrogen, 0.3 per cent phosphoric acid, 0.44 per cent potash, 83 per cent water. Wet and cold, it is better for light soils than heavy clays. Should be mixed with absorbent straw, peat, leaves, etc., to avoid loss of nutrients, and stored under cover. When rotted, good for all soils. Use 100 lbs. per 8 to 12 sq. yds.
Horse Manure. Average analysis: 0.76 per cent nitrogen, 0.56 per cent phosphoric acid, 0.65 per cent potash, 62 per cent water. More fibrous than cow manure, rotting more readily, and well suited to all soils, especially heavy clays, and for the making of hotbeds and Mushroom compost. Use at 100 lbs. per 10-15 sq. yds.
Pig Manure. Average analysis: 0.3 per cent nitrogen, 0.35 per cent phosphoric acid, 0.45 per cent potash, 85 per cent water. Being wet and caustic when fresh, it is only suitable in this state for use on vacant ground. It is best composted with absorbent material before use at 100 lbs. per 8-12 sq. yds.
Poultry Manure. Average analysis: 1.8 per cent nitrogen, 1.0 per cent phosphoric acid, 0.5 per cent potash, 55 per cent water. Comparatively rich, but should only be used fresh on vacant ground. Use at 100 lbs. to 25-40 sq. yds. Best composted with organic material for use at 100 lbs. per 10 to 15 sq. yds. on all soils. May be dried and pulverized for use at 100 lbs. per 5070 sq. yds. Droppings from ducks, hens, geese, pigeons or turkeys are all valuable and should be conserved.
Rabbit manure and excreta from animal pets have manurial value, but as they are usually available in small amounts, they are best added to a compost heap and rotted before use.
Pulverized and Shredded Manures. Dehydrated and pulverized sheep, goat and poultry manures and dehydrated and shredded cow manure are offered for sale and are effective fertilizers but they are not usually applied in sufficient quantities to add very large amounts of humus to the soil. The sheep, goat and cow manures normally contain 1-2 per cent nitrogen, 1-2 per cent phosphoric acid and 2-3 per cent potash. The poultry manures usually analyze 56 per cent nitrogen, 2-3 per cent phosphoric acid and 1-2 per cent potash.
Other Sources of Bulk Humus
Animal manures are invaluable for their humus, but, when they are unobtainable, other humus-forming materials should be substituted. Among these are:
Compost. Compost derived from vegetable
waste, plant remains, etc., that have been rotted or decomposed, has manurial value lower than good manure but adds valuable humus and, with the addition of fertilizer, may be used freely as a substitute for animal manure.
Hair. 2-8 per cent nitrogen. A waste product of tanneries, which may be used in autumn and winter at 100 lbs. per 100 sq. yds. It requires balancing with phosphatic and potassic materials.
Hops. Spent hops from the brewery have negligible nutrient value but are excellent for their humus, and may be applied at 100 lbs. per 10-12 sq. yds. in fall.
Leaf Mold. Plant food values are very slight, but humus-forming properties are excellent. May be used at 100 lbs. per 12-15 sq. yds. Oak or beech leaf mold is best.
Leather Waste. 5 per cent nitrogen. Usually available in clippings or dust form, and may be used at 100 lbs. per 20-40 sq. yds. in fall, but needs phosphatic and potassic supplements for balanced nutrition of crops. Useful on all soils, but especially on light sandy ones.
Feathers. 8 per cent nitrogen. May be used in the same way as hair in the fall, and at similar rates.
Seaweed. Average analysis: 0.5 per cent nitrogen, 0.1 per cent phosphoric acid, 1.0 per cent potash. Rots readily, and may be used freely on all soils at 100 lbs. per 8 sq. yds. in fall or early spring. Requires a phosphatic fertilizer to balance its plant food values properly.
Peat. Plant food content negligible, but humus-forming. Sedge and Sphagnum Moss peats are most valuable for garden use, at 100 lbs. per 1220 sq. yds. in fall or spring and as surface mulches.
Wool Waste. The waste material of woolen mills, but not of cotton mills, is useful as a slow-rotting manure with a nitrogen content of 2-8 per cent. It should be applied in autumn or early winter, at 100 lbs. per 40-60 sq. yds. In addition to its nitrogen content it provides potash in amounts ranging from 0.25-5.5 per cent.
Castor Pomace. This by-product of the manufacture of castor oil has the same uses as cottonseed meal. It contains 5-6 per cent nitrogen, 2 per cent phosphoric acid and 1 per cent potash.
Cottonseed Meal. This by-product of the manufacture of cottonseed oil contains 6-9 per cent nitrogen, 2-3 per cent phosphoric acid, and 1.5-2 per cent potash. It is an excellent slow-acting fertilizer. It has an acid reaction.
This is provided by sowing a quick-growing crop and digging it into the ground before it arrives at maturity, i.e., when it will provide the greatest bulk and yet is not too tall to turn under. The green plants decay in the soil and provide humus which is essential to promote fertility and make the soil fit for plants. Humus, by the action of bacteria in the soil, is further reduced into fertilizing salts, so green manuring may be regarded as a method of holding plant foods in the soil. On light land this holding power becomes of high importance since light, porous land that lies idle for any length of time is apt to lose its soluble food matter through the action of rains. The green manure plants absorb these soluble plant foods and make them available again later as they slowly decay.
Bulky plants, dug into heavy ground, break up the stiff soil, and leave it more porous and friable. As animal manure becomes scarcer every year, green manuring should be practiced regularly when land becomes vacant.
Green manuring is carried out as far as possible between the interval of clearing away one crop and planting or sowing another. There is no need for delay; as soon as a crop is cleared the seed of the green manure crop may be sown. The seed must be cheap and the plants must grow quickly and provide bulk. The seed is simply broadcast over the ground and raked in.
What to Sow for Green Manure. One ounce of seed per square yard of ground is the usual sowing rate. The plants chiefly grown are Rape, Mustard, Italian Rye Grass, Buckwheat, Cow Peas, Vetches, and Winter Rye. Rape and Mustard are not recommended for use where Turnips or Cabbages have been grown previously. Rye Grass takes rather longer to grow than the others. Vetches and Cow Peas are recommended for another reason. Like all the leguminous plants, they have the power of fixing nitrogen in the nodules on their roots; this serves to enrich the soil by adding to its nitrogenous content. If when the crop is ready to be dug in there is any difficulty in doing the work, the plants should be rolled down first. A sprinkling of sulphate of ammonia on the green material as it is dug in, will assist its rapid decay.
These may be divided into the organic, and the inorganic or chemical. The organic fertilizers are usually of animal origin and are held in high esteem by gardeners for intensive soil cultivation, as their regular use tends to increase fertility ac-cumulatively.
The chief purpose of fertilizers, however, is to provide plant nutrients in concentrated form to stimulate plant growth, increase yields, and offset soil deficiencies. According to the rapidity with which their nutrients become available to plants in the soil, they are termed quick, steady, or slow-acting; and this determines the appropriate time for their application. For practical purposes most fertilizers may be divided into three classes according to whether the chief element they supply is nitrogen, phosphorus, or potash. In addition there are fertilizers, such as Nitrate of Potash, that provide two fertilizing elements and others, called complete fertilizers that supply all three.
Nitrogen is essential to the protoplasm or living substance of plant cells, and vital to growth. Too much, however, produces sappy, dark-green top growth and delays ripening; too little causes stunting, and yellowing of foliage. As nitrogenous compounds are readily lost from soils, regular replacement is needed.
Dried Blood (12-14 per cent nitrogen) is organic. Dried blood is quick-acting, for spring and summer use at 2 oz. per sq. yd., or as liquid in water at 0.5-1 oz. per gallon. Acid-reacting.
Hoof and Horn Meal (12-14 per cent nitrogen) contains traces of phosphorus and other elements, and acts steadily. Good on all soils, applied in fall or early spring at 2 oz. per sq. yd. Excellent for soil composts for potting.
Tankage (6-11 per cent nitrogen), if pure, supplies mainly nitrogen, but if containing ground bones supplies phosphoric acid, also (8-20 per cent). May be used at 2 oz. per sq. yd. in winter or early spring. Alkaline reacting.
Fish Meal (8-10 per cent nitrogen, 4.5-9 per cent phosphoric acid, 2-3 per cent potash) is marketed under various brand names, and makes a general balanced fertilizer for use in spring according to makers' recommendations.
Guano (10-14 per cent nitrogen, 8-10 per cent phosphoric acid, 2-4 per cent potash), consisting of the excreta of sea birds, is excellent for spring use at 2-3 oz. per sq. yd., and as a summer food for growing plants at 1 oz. per gallon water. Proprietary "guano," unqualified by the term Peruvian, should be used according to the makers' recommendations.
Sewage Sludge. Dried, processed sewage, now offered by some municipalities, has considerable nutrient value. The analysis varies according to the type of processing. It is good when used according to the recommendations of the processor. One of the best-known of these processed sewage sludges is Milorganite, which contains 6 per cent nitrogen and 2.5 per cent phosphoric acid, and traces of potash.
Nitrate of Potash (12-14 per cent nitrogen, 44-46 per cent potash) is saltpeter. Quick-acting, but expensive, it is used chiefly as a greenhouse and pot plant liquid fertilizer, at 0.5 oz. per gallon water.
Nitrate of Soda (15.5-16 per cent nitrogen) is a quick-acting fertilizer, valuable for spring and summer use, either at 0.5-1 oz: per sq. yd., or in water 0.25-0.5 oz. per gallon. Being deliquescent, it makes clay soils more sticky. Caustic if allowed to fall on foliage. Alkaline reacting.
Calcium Nitrate (15.5-16 per cent nitrogen, 48 per cent calcium carbonate) is a granular fertilizer, quick-acting and excellent for spring and summer use on soils that are too acid at 1 oz. per sq. yd. Alkaline reacting.
Soft Coal Soot (1.6 per cent nitrogen) is caustic when fresh, and in that state should only be applied to vacant ground. If allowed to stand 2-3 months under cover, it may then be used as a fertilizer at any time of the year at rates of 4-8 oz. per sq. yd. It acts as a good slug deterrent.
Sulphate of Ammonia (20.6 per cent nitrogen) acts fairly quickly, and may be used in spring or summer at 0.5-1 oz. per sq. yd. Acid-reacting, it should be used with care on acid soils, which should be adequately limed beforehand except for acid-soil plants.
Urea is made synthetically. It contains 46 per cent nitrogen, a much higher proportion than is found in any other solid fertilizer. Repeated use of urea has a slight acidifying effect. The nitrogen in it is rapidly available to plants.
Urea-form Fertilizers are synthetic combinations of urea and formaldehyde. They, possess the property of releasing their nitrogen slowly over a long period and in this respect more closely resemble organic manures than does any other synthetic source of nitrogen. When they are applied in spring the plants benefit from the nitrogen
they release over a period of many weeks. These fertilizers are sold under many different trade names.
Phosphorus aids root activity, ripening and maturing of plants. If it is deficient, plant growth is stunted, and foliage becomes dull. Phosphatic content is expressed in terms of phosphoric acid. In addition to the fertilizers listed below, phosphorus is also supplied by some of the fertilizers listed above under Nitrogen Fertilizers.
Basic Slag (9-18 per cent phosphoric acid) is slow-acting and alkaline. Quality is variable.
Slags of 80 per cent or over solubility of phosphoric acid in citric acid are good; 50 per cent or less solubility means very slow release of phosphates for plant nutrition. Apply in autumn or winter, at 4-8 oz. per sq. yd. Encourages clover in grasslands.
Raw Bone Meal (20-24 per cent phosphoric acid, 3-4 per cent nitrogen) is invaluable for all
crops and plants. Slow-acting, with an alkaline reaction, it may be applied in fall or early spring at 4-8 oz. per sq. yd. The more finely ground the meal, the more quickly its nutrients become available.
Steamed Bone Meal (22-30 per cent phosphoric acid, 1 per cent nitrogen) is finely ground and
acts relatively quickly. Use at 2-4 oz. per sq. yd. in late winter or early spring. Good for mixing with other fertilizers to prevent caking.
Superphosphate (16-18 per cent phosphoric acid) is a quick-acting fertilizer for use in early
spring or summer at 1-2 oz. per sq. yd., and for seed composts. Double superphosphate (40-48 per cent phosphoric acid) is more concentrated, for use at 0.5 oz. per sq. yd.
Ground Phosphate Rock (26-38 per cent phosphoric acid) is the mineral rock finely ground. Very slow-acting, it should be applied in autumn or winter at 3-4 oz. per sq. yd.
Potash increases resistance of plants to disease and inclement weather. A common deficiency symptom is marginal browning or scorching of plant leaves. In addition to fertilizers listed below, potash is also supplied by some of the fertilizers listed above under Nitrogen Fertilizers, which see.
Kainite (14 per cent potash, 50-60 per cent sodium chloride, 20 per cent magnesium sulphate) is slow-acting, for use in autumn or winter at 2-3 oz. per sq. yd., but care is needed on clay soils for too heavy applications may be harmful.
Muriate of Potash (50-60 per cent potash, 15 per cent sodium chloride) is rather slow-acting, for use in autumn or winter at 0.5-1 oz. per sq. yd. Interchangeable with sulphate of potash, generally, but not for Tomatoes, Potatoes, Roses or greenhouse use. It is less refined than sulphate of potash.
Sulphate of Potash (48.5 per cent potash) acts readily, and may be used at any time at 0.5-1 oz. per sq. yd. The best potassic fertilizer to use anywhere in the garden.
Potash Salts (20-30 per cent potash) are natural mineral rock finely ground; slow acting, and for use, according to potash content, at 1-2 oz. per sq. yd., in autumn or winter.
Wood Ash (5-25 per cent potash, 2 per cent phosphoric acid, 30-35 per cent lime) varies considerably. Hardwood ash is best. May be used at 4-5 oz. per sq. yd. at any time of the year, but must be collected dry and kept dry to retain its full potash content.
Fertilizers that supply one or two of the three important nutrient elements may be used alone when the crop is judged to need only that element or those elements at the particular time the fertilizer is applied, but often it is desirable to mix more than one fertilizer together to obtain balanced nutrition. Mixed fertilizers may be purchased ready-prepared or can be compounded at home according to recommended formulae. In the latter case, care should be taken not to mix calcium nitrate or sulphate of ammonia with lime, or basic slag, or superphosphate with nitrates, lime, or substances containing free lime.
Complete Fertilizers are those that provide all
three major fertilizing elements, nitrogen, phosphoric acid and potassium. Complete fertilizers may be entirely organic, entirely inorganic, or consist of a mixture of organic and inorganic materials. Cottonseed Meal, Castor Pomace, Fish Meal, Guano, and Sewage Sludge are organic complete fertilizers. Inorganic complete fertilizers are prepared by mixing together inorganic fertilizers, each of which contains one or more of the elements nitrogen, phosphorus or potassium in such proportions that the resulting mixture provides the plants with all three.
It cannot be truly said that organic fertilizers are better than inorganic; nor that the reverse is true. The particular purpose for which they are needed often determines their suitability. The great advantage inorganic fertilizers have is their ready availability and quick action; their common disadvantage is their lack of "staying power." (An exception are the urea-form fertilizers; see Nitrogen Fertilizers, above.) More frequent applications are usually necessary than is the case with organic fertilizers. These latter usually dispense their nutrients more slowly and so serve the plants over a longer period; on the other hand they are slower acting and hence less useful for "shot-in-the-arm" treatments. Many complete, commercially prepared fertilizers are part organic and part inorganic.
Fertilizer formulas are commonly expressed by three figures separated by dashes in this fashion, 5-10-5. These figures indicate the proportions in which the available nutrient elements are present. The first number refers to nitrogen, the second to phosphorus and the third to potassium.
When considering complete fertilizers, attention must be given to these figures and also to their ratio one to the other. For example, a fertilizer analyzing 10-20-10 would contain twice as much of the nutrient elements per unit as one having a formula 5-10-5, but the proportions are identical and as it would be necessary to apply only half as much of the concentrated one to the plants as of the less concentrated, they would receive exactly the same fertilization. An advantage of the 10-20-10 is that it is less weighty and less bulky; on the other hand, the 5-10-5 might be less than half as costly for a given weight, and thus actually cheaper.
A fertilizer analyzing 5-10-10 is proportionately much richer in potash than a 5-10-5 or a 10-20-10 and would be advantageous to use if root stimulation were needed. If heavy foliage growth were the desired end, a fertilizer proportionately richer in nitrogen and phosphorus such as a 6-10-4 might be chosen. Sometimes, as when it is desirable to stimulate flower production rather than foliage, a low-nitrogen formula is likely to be advantageous; for this purpose some such formula as 0-10-5 or 2-10-5 would serve.
In recent years highly concentrated, completely soluble fertilizers having formulas as high as and higher than 15-30-15 (note this particular one provides the essential elements in exactly the same proportions as 5-10-5) have become available. Because they leave no residues, they are very suitable for house plants and other pot plants. They are the types most commonly used for foliar feeding.
Foliar Feeding is the application of liquid fertilizer to plants through their leaves. The materials mostly used are concentrated sources of nitrogen, phosphorus and potassium that are highly soluble and readily dissolve in water. The solution is sprayed on the leaves either with a sprayer, or with a watering can. Foliar feeding relies for its effectiveness on the ability of
the leaf to absorb the fertilizer materials, which then directly enter the cells and become assimilated without the aid of the roots. This ability, or power of absorption, varies with the kind of plant. Not all plants have the same ability to take in fertilizers through their leaves. Other factors affecting the intake of fertilizer through the leaves are the age of the leaf, the season, and the kind of weather prevailing at the time of feeding. The strength of the solution and the quantity that can be effectively used vary with the kind of plant. The amateur should purchase named brands and use them as recommended by the manufacturer.
Trace Elements. In addition to nitrogen, phosphorus and potash, plants require a number of other nutrient substances for their proper growth. Many of these are needed in extremely small amounts but their absence, or a deficiency of them, may have a marked detrimental effect on the plants.
In the vast majority of garden soils these so-called trace elements are present in adequate amounts or they are supplied in sufficient quantities by the presence of slight amounts in other fertilizers and manures applied to the soil. Because the presence of some of these in too great concentrations is harmful, they should not be added unless an analysis of the soil shows that they are needed or unless the garden is in a region where the State Agricultural Experiment Station advises their use.
Trace elements that sometimes need to be added are iron, manganese, boron, copper and zinc.
Other elements that are sometimes deficient and may be added upon the advice of competent specialists are sulphur, calcium (usually applied in the form of agricultural lime) and magnesium.