1676 



SOIL 



of the physical properties upon the water supply, and 

 the commercial values of many soils are dependent 

 largely upon this one condition. This is notably the 

 case with the early truck crops, with corn, wheat and 

 grass lands, and with special products such as celery, 

 cranberries and other horticultural crops. With inten- 

 sive cultivation, however, the flavor, appearance, tex- 

 ture and general quality of the crop assume greater 

 commercial importance, and even with intensive meth- 

 ods these are largely influenced by the character of the 

 soil. This is shown in a striking manner in the locali- 

 zation of certain interests, even under the most inten- 

 sive system of agriculture, such as the production of 

 the fine lettuce around Boston, of the carnations, vio- 

 lets, tomatoes and roses in other districts. With the 

 present specialization in these lines, it is not only neces- 

 sary that one should have a knowledge of the methods 

 of cultivation, but should have the proper soil condi- 

 tions as well as suitable climatic conditions; and to 

 such an extent has this specialization been carried that 

 different varieties of roses, for example, are best grown 

 in different localities where the soils are slightly differ- 

 ent. These matters must be realized by the horticultur- 

 ist in order to attain the highest degree of success in 

 any particular undertaking. MILTON WHITNEY. 



SOILS FOE POTTING. Strictly speaking, there are but 

 two distinct kinds of soils, though there are several 

 modifications or physical differences in both. These are 

 mineral soils and organic soils or peat. Peat is formed 

 in temperate climates by the accumulation of vegetable 

 matter in swamps, or in some parts of the world under 

 peculiar atmospheric conditions (see Peat). Mineral 

 soils, which cover the greater portion of the earth's 

 surface, are formed by the disintegration of rocks and 

 stones through the agency of water, frost or the atmos- 

 phere. Peaty soils are composed almost entirely of 

 vegetable matter, with but little mineral matter. Min- 

 eral soils are just the.reverse. The physical differences 

 in peat are practically reduced to two; viz., the ab- 

 sence or presence of fiber. The physical differences in 

 mineral soils vary considerably from almost pure clay 

 to almost pure sand; indeed, the mechanical (or physi- 

 cal) analysis of mineral soils is based largely upon the 

 proportions of clay and sand. The following table, 

 taken from Tanner's "First Principles of Agriculture," 

 is self-explanatory: 



Name of soil Percentage of sand 



Sand 80 to 100 



Sandy loam 60 to 80 



Loam 40 to 60 



Clay loam 20 to 40 



Clay to 20 



It will be seen that when the proportions of sand and 

 clay are equal or nearly so, the soil is then termed loam. 

 Should clay or sand predominate it is then spoken of as 

 a clay loam, or sandy loam. If other substances, such 

 as lime or gravel, be present, the soil is then termed a 

 calcareous or a gravelly soil. 



The composition of soils can be still further known 

 by chemical analysis, but to the average gardener this is 

 not necessary. Moreover, it is an operation of great 

 nicety and one that requires an experienced chemist to 

 perform. The chemical constituents which plants derive 

 from the soil are present in most soils, though in vary- 

 ing degree, but they are sure to be present in ample 

 quantity in the potting soil selected by an experienced 

 gardener. The air and water may furnish as much 

 as 98 per cent of the material with which the plant 

 body is built up in some cases, and only the remaining 

 2 per cent be strictly derived from the soil. The three 

 most important nutrient elements are nitrogen, phos- 

 phoric acid and potash. Of the three, nitrogen is the 

 most important, but all are present in varying degrees 

 in most natural manures. Moreover, nitrogen composes 

 four-fifths of the atmosphere and the soil absorbs it 

 chemically through the action of bacteria when the soil 

 is in good physical condition. Hence the importance of 

 remembering always that air in the soil is as important 

 as water. Sorauer, in his "Physiology of Plants," page 

 56, says: "The ideal condition of a soil is one in which 

 it resembles a sponge, and in which it will retain the 

 greatest amount of nutritive substances and water with- 



SOIL 



out losing its capacity for absorbing air." Therefore it 

 will readily be seen that the physical condition of soil is 

 far more important to the gardener than the chemical. 



Mineral soils vary according to locality, but when the 

 topography of any particular locality is of a hilly or 

 mountainous character, the different variations or phys- 

 ical differences may often be found within the radius 

 of a mile. The capacity of soils to retain moisture va- 

 ries considerably. A clay loam is far more retentive of 

 moisture than a sandy loam. The experienced gardener 

 therefore selects a clay loam for his strong-rooting, 

 large-leaved tropical plants, because transpiration is so 

 much greater in these plants, .tor a general collection 

 of greenhouse and small-growing tropical plants he 

 selects a good loam. For cacti, agaves and other succu- 

 lent plants which will not take as much water at all 

 seasons as other plants, he selects a sandy loam. For 

 ferns, most of the Ericaceae and Gesneraceas he selects 

 peat; while for nepenthes, orchids, bromeliads and the 

 epiphytic aroids he selects fern or kalmia root. Other 

 materials which a gardener should always have on hand 

 when he has a large and varied collection of plants are : 

 leaf-mold, which is made by collecting leaves and stor- 

 ing for at least two years, turning them over occasion- 

 ally to facilitate decay; living or fresh sphagnum moss; 

 sand; charcoal, and some convenient manures, such as 

 pulverized sheep manure and bone meal. 



Growing plants in pots is very different from grow- 

 ing them in borders or the open ground. In pots, espe- 

 cially the larger sizes, the capacity of the soil for ab- 

 sorbing air is in a great measure restricted ; therefore, 

 the experienced gardener digs the turf only from good 

 pasture or meadow land, so that it shall be full of the 

 fibrous roots of the grass. Soils containing fiber will 

 absorb air much more freely than that without fiber. 

 But before using the turf for potting it should be placed 

 in square piles, turf downwards, for at least six months 

 in order to kill the grass and all vegetable life. Fern 

 root should also be collected and stored the same length 

 of time in order to kill out the ferns. Fig. 2333. Raw 

 and very coarse soils are usually sifted before used for 

 most greenhouse plants. Shallow sieves are used for 

 this purpose. Fig. 2334. 



2334. Sieves for sifting or riddling soils. 



Except for sowing seeds and for potting seedlings 

 and freshly rooted cuttings, thoroughly decayed and 

 homogeneous soils should not be sifted, but should be 

 broken into small lumps, as the small lumps assist ma- 

 terially in aerating the soil. If the soil is sifted too 

 much it becomes very fine, packs close and allows too 

 little aeration. Leaf-mold is decayed vegetable matter, 

 or humus. It may have little manurial value, but is used 

 by gardeners to make soils "light" or spongy. For most 

 young plants a good proportion added to the soil is ex- 

 cellent, as it encourages root growth. 



Sand is the best medium for rooting cuttings of the 

 majority of plants. It is also added to soils to increase 

 their porosity, especially when potting very young 

 plants. Silver sand is best for all purposes because it 

 contains less oxides than red or yellow sands. 



