SOIL 



SOILS 



3179 



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 

 varying 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. Three import- 

 ant nutrient elements are nitrogen, phosphoric acid, 

 and potash. 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 resem- 

 bles a sponge, and in which it will retain the greatest 

 amount of nutritive substances and water without los- 

 ing its capacity for absorbing air." 



The capacity of soils to retain moisture varies con- 

 siderably. A clay loam is more retentive of moisture 

 than a sandy loam. The experienced gardener there- 

 fore selects a clay loam for his strong-rooting, large- 

 leaved tropical plants, because transpiration is so 

 much greater in these plants. For 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 Gesneraceae, 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. The expe- 

 rienced gardener digs the turf only from good pasture 

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

 roots of the grass. But before using the turf for pot- 

 ting it should be placed in square piles, turf down- 

 ward, for at least six months in order to kill the grass 

 and all vegetable life. Fern root should also be col- 

 lected and stored the same length of time in order to 

 kill out the ferns. (Fig. 3625.) Raw and very coarse 

 soils are usually sifted before being used for most 

 greenhouse plants. Shallow sieves are used for this 

 purpose. (Fig. 3626.) 



Except for sowing seeds and for potting seedlings and 

 freshly rooted cuttings, thoroughly decayed and homo- 

 geneous soils should not be sifted, but should be broken 

 into small lumps, as the small lumps assist materially 

 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 excellent as it encourages root-growth. 



Sand is the best medium for rooting cuttings of the 

 larger number of plants. It is also added to soils to 

 increase their porosity, especially when potting very 

 young plants. Silver sand is best. 



In potting plants, experienced gardeners make pot- 

 ting mixtures or add a variety of materials to the soil to 

 suit the requirements of different plants. For young 

 seedlings or for freshly rooted cuttings, the compost 

 should be of a light and porous nature, but as plants 



increase in size and vigor a heavier and richer mixture 

 is usually given, that is, if plants are to be grown on as 

 specimens; but the proportion of nutrient substances 

 used in a potting mixture should be determined by the 

 vigor of the plants. It is always better to use too little 

 plant-food than too much; if too much is used it often 

 becomes available faster than the roots of plants can 



3626. Sieves for sifting or riddling soils. 



absorb it, often with fatal results. Many amateur 

 plant-growers in their over-anxiety to grow fine plants 

 make this fatal mistake. 



In most gardens the greenhouse space is limited, and 

 a gardener cannot always develop his plants to their 

 fullest capacity or he has to reduce his variety and 

 numbers. This, then, determines in the mind of an 

 experienced gardener the composition of his potting 

 mixtures. His aim should be to grow the finest possible 

 specimens in the smallest possible pots and space. 



EDWARD J. CAXXIXG. 



SOILS, STERILIZING. Greenhouse and plant-bed 

 soils are specially liable to infection by disease organ- 

 isms, as they are intensively cropped and not exposed 

 to the action of frost and weather. Careful growers 

 now resort to methods of artificial sterilization. 



In practice, the sterilizing is accomplished either by 

 heat applied by live steam, or by a chemical process 

 employing a formalin drench. In either case, the work 

 must be thoroughly performed if satisfactory results 

 are to be expected; it will be required at least as often 

 as every other year, and the situation is safer if steriliz- 

 ing is practised annually. 



Steam sterilizing is of two methods: by buried per- 

 forated pipes, and by a pan inverted over the soil and 

 under which the steam may be conveyed. The latter 

 is probably preferable in most cases. In either case, 

 live steam should be applied for an hour or more. 



"The perforated pipe method appears to consist, at 

 its best," according to Selby and Humbert in Circular 

 Xo. 151 of the Ohio Experiment Station, "in a system 

 or set of perforated pipes, with crosshead and high- 

 pressure boiler connection. These pipes are connected 

 and buried in the soil of the bed, either with or with- 

 out partial banking up of the soil; the surface of the 

 bed is then covered with canvas or other covering and 

 the steam passed into the system for such a period as 

 is required to heat the soil to the necessary tempera- 

 ture. This temperature for best results is 180 to 212 

 F. maintained for a period of an hour or more. The 

 time required to reach this temperature will vary 

 with the boiler area, the pressure and other steam and 

 soil factors. The length of pipes of the system will be 

 adapted to the beds, being one-half or one-third the 

 total length of large beds. Generally, IJ^-inch pipe 

 is used with }/-inch holes bored in a straight line about 

 1 foot apart. These pipes are buried in the beds 12 to 

 16 inches apart." 



