An abundance of organic matter tends to improve drainage, increase the capacity of the soil for holding water, enhance the cultivation of clayey soils, and aid the moisture retention of sandy ones.
Cow manure is the least heating of the readily available manures and is especially good for roses, lilacs, and plants that do not respond to heating manures or to heavy supplies of ready nitrogen. Horse manure is probably the most beating of the commoner manures. Chicken, rabbit, and sheep manures are rich in nitrogen and should be used moderately lest they cause soft growth or growth too late in the season, which would leave the plants to be caught by cold weather.
Except for nitrogen, potassium, and phosphorus, and occasionally lime and magnesium, the chemical elements which constitute plant food usually are sufficiently present in average soils for plant growth. Nitrogen is the one usually most required and also the one most likely to be lacking.
Here are the qualities attributed to the chemical elements:
If one is lacking, the others do not function properly.
As to commercial fertilizers, the following discussion has been published by the United States Department of Agriculture:
Best results are obtained by making sure that an abundance of plant food is available. Because organic matter is of first importance, manures should have first consideration, followed by mixed fertilizers, preferably those with an organic base, in order to supply as much organic matter as possible. Such fertilizers have comparatively low analyses, but a low analysis does not of itself mean that the fertilizer is made from organic constituents. A statement to the effect that organic materials are a source of specified parts of the mixture should be a part of the guarantee under which the mixture is purchased.
With every fertilizer offered for sale, a guarantee of its analysis is required. This includes a statement as to the quantity of nitrogen expressed as ammonia (NH,), as nitrogen (N), the phosphorus in terms of water free or anhydrous phosphoric acid, and potassium in terms of potash. In most states these are given in the order named, for instance, a 4-8-4 means 4 per cent of nitrogen, 8 per cent of phosphoric acid, and 4 per cent of potash.
Commercial fertilizers range from a total
plant-food content of less than 10 per cent to over 50 per cent. Where
a purely inorganic fertilizer is to be applied, it would be economical
to use the higher grades, for the proportion of inert material in them
is much less, and thus reduce the weight on which freight is to be paid,
and also the number of bags necessary to hold 100 pounds of plant food.
Of course, the richer fertilizers are used in smaller quantities, and
more care must be exercised to avoid getting the material on foliage or
in too close contact with the roots.... where laborers instead of gardeners
with special training are likely to be employed, manures and organic rather
than inorganic fertilizers bad best be applied, because there is less
danger of injury if these materials are improperly handled.
Rates of application
The quantities of these materials which are desirable or can safely be applied vary greatly. Dried stockyard cattle and sheep manure can be safely and often advantageously applied up to 2 tons per acre or 1 pound for 10 square feet; cottonseed meal, soybean meal, ground bone or bonemeal, up to 1 ton per acre or 1 pound for 20 square feet; dried blood, tankage, and fish scrap, one-half ton per acre or 1 pound for 40 square feet; a 5-10-5 mixed fertilizer, a 16 per cent superphosphate, and other fertilizers of similar grade, 500 pounds per acre or 1 pound for 80 square feet; and concentrated fertilizers, such as triple superphosphate, a 10-20-10 mixture, urea, cyanamide, nitrate of soda, and sulfate of ammonia, 200 pounds per acre or 1 pound for 200 square feet. Nitrate of soda and sulfate of ammonia being very soluble may often be used more advantageously by applying 50 pounds per acre or 1 pound for each 800 square feet at intervals of a month or 6 weeks. . . .
On poor soils a wise practice is to apply liberally a well-balanced fertilizer and then if there is doubt as to its proportions for the purpose use a little excess of one of the ingredients on a small portion of the plantation, and the elements usually deficient on other portions, and note the results. It is well to keep in mind the order in which the deficiencies arc most likely to occur-nitrogen, phosphoric acid, and potash; and when it is not possible to test for all three elements, begin with nitro unless individual or community experience suggests that another element may be the one most needed.
Excepting nitrate of soda and sulfate of ammonia, these materials give best results if applied just before rather than at the close of the dormant season. It is inadvisable to apply them at a time when the soil is likely to remain dry. In dry regions they should not be used at the beginning of the dry season unless irrigation is to follow. They may be worked into the soil or be broadcast on a lawn or a mulch. Because nitrate of soda and sulfate of ammonia are very soluble they are easily leached from the soil. Therefore, they should be used only in small applications on a mulch where their caustic action will hasten the conversion of the mulch into plant food or they should be applied directly to the soil or on a lawn where the roots are active, so that a maximum of the material will be utilized promptly. Both these substances absorb water with great avidity; hence they must not remain in contact with living plant tissues for even a short time, or the tissues will be burned. If these salts are free from lumps they may be sown broadcast on soil that is covered . . . with grass or other ground cover if thoroughly wet from recent rains; or they may be sown on turf or other ground cover if the application is immediately followed by a drenching. Perhaps a safer way is to dissolve them at the rate of 1 pound to 10 or 20 gallons of water, following this application with a good watering.
Nitrate of soda usually acts more quickly than sulfate of ammonia, and produces an alkaline rather than an acid soil reaction. Sulfate of ammonia is supposed to act over a long period. Both of these substances are especially valuable for application to plants weakened by transplanting, severe pruning, disease, starvation, or malnutrition.
Whatever is used, be sure to work it into the soil thoroughly, bearing in mind, however, that, unless the ground is reasonably good to begin with, especially in texture, even the best of fertilizers will not bring the most satisfactory results.
The soil should be virtually a sponge in its capacity to supply water to the plants. A garden must have a proper water supply. A deep soil well supplied with organic manure creates a reservoir for the plants. It can absorb a large amount of water whenever it has the opportunity and also surrender the water to the plants as they need it. At the same time, when the soil has absorbed all the water it can hold, it must have drainage to carry off the surplus.
Water can drain naturally from higher ground to lower ground, that is, down a hill, or artificially, by pipes or troughs. In poorly drained soils, dig the bed 3 feet deep instead of 2 feet, line the bottom with a layer of stones to a depth of 1 foot cover the stones with inverted sod, and cover them with 2 feet of the prepared soil. The drainage layer should have a proper outlet, such as a drainpipe or a stone drain.
Watering the garden
In normal seasons the natural rainfall of a large part of the United States is sufficient for a well-prepared bed. Beds which are sheltered from much of the natural rainfall, however, such as beds close to a house, require supplementary watering. In dry climates, even in moist climates during unusual dry spells, and also in sandy or other unusually dry soils, irrigation will be necessary.
Dryness of soil and dryness of atmosphere determine the amount and frequency of watering. With the possible exception of areas of excessive evaporation, such as in the driest parts of the United States, a weekly watering is all that a well-prepared, retentive soil, 2 feet deep, should require.
If the soil is sandy or gravelly, and especially if it is not well fed with organic matter, it may need a thorough watering every other day. Experience alone will yield the best indication of the frequency of watering, but this rule should be kept in mind-water as infrequently as soil and climatic conditions allow.
Unusual drying conditions or neglect for a day may dry out the feeding ground and kill the roots. Watering too frequently keeps the surface soil moist and makes for root growth near the surface. If the roots are forced to go deeper by letting the surface become dry for 2 or 3 inches between waterings, unusual conditions and slight departures from a regular watering schedule carry less danger.
Sprinkling is not the wisest practice unless it can be carried on for long periods, because it is a very deceiving labor that usually just wets the surface. Let the stream hit the ground at an angle. Water deeply each time; wait until the ground has become fairly dry, then soak well. Water the bed in the morning or wait until after the hottest part of the day to prevent scalding. Roses watered in the afternoon will develop mildew or spots.
When new plants are set in the garden it is usually a good idea to dig a generous hole in the ground, fill it with water and a little soil, put in the plant, water again, and sprinkle a little dry soil on top or mulch to prevent drying. With this method one watering is usually sufficient. If the plant shows signs of flagging, water it well. Be careful to set new plants only as deeply as they previously were set.