Ami I, m^.j fm f^QPitAt A5KietJtWRI8f, 



66 f 



^f!tt=^is(iiBi 



3. In what respects do soil and subsoil differ? 



4. Explain the tollowing terms: — Weathering, Denu- 

 dation. Alluvium, Drift, Nitrification. 



5. (Jive a brief statement of the physical proper- 

 ties of soils. 



6. What are the physical properties of (a) clay 

 soils, (/') chalk soils, {cj sandy soil?, (d) peat soils? 



7. How is fertility of soil influenced by (1) mech- 

 anical texture, (2) climate and local conditions? 



8. What practically determines fertility of soil ? 

 9- Distinguish (1) between a barren soil and a soil 



exhausted and (2) between natural a.nd acquired fev- 

 tiiity. 



10. How are soils classified? 



11. What soils and conditions of soils possess the 

 power of capillary attraction in the highest degree; and 

 what is its importance as regards drainage, the retention 

 of moisture, and the supply of that moisture, to the 

 growing p'ants? 



12. State some of the principal causes uf infer tiiity 

 iu soils. 



13. Is there a ready test for ascertaining the pre- 

 sence of injurious constituents in soils? 



14. Give instructions for a rough mechanical ana- 

 lysis of a soil. 



15. What is meant by exhaustion of soil, and what 

 causes it ? 



IG. Mention (a) the surface distribution, and (b) 

 the agricultural characters of (1) silurian, (2) old and 

 new Red Sandstone, and (3) Greensand soils. 

 ANSWEKS. 

 1.— Soils. 



1. The mineral and organic matters forming the 

 crust of the earth are the origin of all soils. The 

 inorganic or mineral portion of the soil is derived 

 from the crumbling down of the solid rocks, by the natu- 

 ral process of weathering or disintegration, which is fa- 

 voured by warmth, and the presence of moisture and 

 organic matter. All rocks, however, are not acted upon 

 with the same ease : but the hardest of them are 

 surely though slowly crumbling into dust under the 

 mighty but invisible agency of the carbonic acid and 

 oxygen of the air. The union of decaying vegetable 

 matter in the soil with the oxygen of the air 

 also helps to promote the decomposition of rocks, — 

 as do frosts, rain, wind, and other kindred forces. 

 These disintegrating agents are further aided by the 

 root-growth of plants, by the burrowing of worms 

 and other earth-dwelling creatures, and in no small 

 degree by the acids generated by organic decay. The 

 organic portion of the soil is derived from the remains 

 of plants and of animals and insects of various kinds. 

 In some cases the soils are purely organic in their 

 origin. These are both plant and animal formations — 

 the former comprising vegetable mould and peat mos- 

 ses ; the latter, beds of chalk and limestione, &;c. 



2. The inorganic or mineral constituents found in 

 all fertile soils are — silica, alumina, calcic carbonate, 

 potash, soda, magnesia, phosphoric acid, sulphuric acid, 

 chlorine, and oxide of iron. The first three— sand, 

 clay, lime— represent perhaps 90 per cent or more of 

 the substance of most soils. The others vary from a 

 mere trace to at most 2 per cent. The organic matter is 

 formed of 0. H. O., and a series of organic acids — 

 humic, ulmic, geic. Sandy soils are generally defi- 

 cient in this ingredient. Cold clays are also poor in 

 organic matter. _ In fertile loams it is more abundant ; 

 and in peaty soils it is usually in excess. Altogether 

 the organic matter in soil varies from 1 to upwards of 

 90 per cent. 



3. In a majority of cases the soil is merely rotted sub^ 

 soil, and differs from the latter chiefly in tlie greater 

 amount of oraganic matter it contains, end in being 

 less compact, and darker in colour. 



4. " Weathering " is the term used to denote the 

 natural disintegration or breaking up of rocks as ex- 

 plained in answer to the first question. " Denudation " 

 is the wasting or carrying away of soils from the 

 place of their original formation by rainfall or sur- 

 face water. " Alluvium " is soil deposit which has 

 been transported from higher to lower levels by the 

 agencies of rivers or tides. " Drift " or botdder clay 

 ii> a wide-ipread surface detritus of tbe diffcrcut for* 



mations, which is affributed to glacial action. "Nitri- 

 fication " is the oxidation of nitrogenous bodies iu 

 soil — humus and ammonia — and their conversion into 

 nitric acid. 



5. The physical properties of soils which may be 

 supposed to exert a grea,ter or less influence on fer- 

 tility have been well stated by Schubler as follows: — 

 (1) The weight of the soil, its specific gravity as 

 well as the absolute weight of a given bulk in a dry 

 and moist state. (2) Its power of containing water, 

 according to its weight and bulk. (3) The firmness 

 and consistence of a soil in its dry and in its moist 

 state. (4) Its different capability of becoming dry 

 on exposure to the air. (5) Its diminution in bulk 

 on drying. (6) Its absorption of humidity from tho 

 atmosphere, (7) Its absorption of oxygen from the 

 atmosphere. (8) Its power of retaining heat. (9) 

 Its capability of becoming more or less warmer by 

 the sun's rays. (10) Its capability of developing 

 heat on being moistened. (11) Its electric polarity 

 and capability of conducting electricity, 



6. A clay soil differs from all others by being 

 tough, wet, and cold. In wet winter weather it sticks 

 to the plough, like mortar, and in dry summer weather 

 it is hard and cloddy, and the surface covered 

 with chinks or cracks. A sandy soil is subject to 

 defects of an opposite description. A chalky or cal- 

 careous soil contains a great deal of carbonate of lime 

 and when wet is of a soapy nature, but is marked by 

 the freedom with which it admits of natural drainage, 

 and warm and productive though white in colour. A 

 peat soil if light and spongy in texture, dark in colour , 

 and very absorbent and retentive of both heat and 

 moisture. 



7. Mechanical texture inliucnces fertility of soil iu 

 a great degree for tho conditions of air moisture, and 

 warmth which are essential to the development of the 

 changes which occur in the process of germination, 

 have little or nothing to do with the chemical qualities 

 of the soil, but are all dependent upon its mechai.ical 

 relations. This influence is not confined to the first 

 stage of vegetation- Climate also exercises a great 

 influence on fertility, and disregard of local condi- 

 tions sometimes leads to very erroneous estimates of 

 the value of soils which may be similar in composi- 

 tion, and texture. 



8. Fertility of soil is practically determined by 

 the minimum of any one essential ingredient and 

 not by the maximum of the others, but intrinsic 

 value depends on the depth of the soil; its mechani- 

 cal texture, situation, altitude, and sorroundiugs, quite as 

 much as on its chemical composition. 



9. The difference between an exhausted soil and 

 a barren soil is this : the former will recover its ferti- 

 lity or be renovated by nature in the course of 

 time if, meanwhile nothinj,' more is carried away from 

 it; whereas a barren soil will continue barren, if 

 the operating causes remain as before. A soil which 

 has once been fertile can never be completely ex- 

 hausted by the cultivator, and the deeper the soil 

 the more superficial will have been its partial ex- 

 haustion. The distinction between natural and ac- 

 qiiired fertility is that the former is a permanent 

 quality and the latter is not. An examination of 

 the soil and subsoil is the only reliable test. The 

 appearance of the crops on arable land is often very 

 misleading, and even in the case of grass land the 

 herbage is not altogether a criterion of the quality 

 of the soil ; if the herbage is poor it may be the 

 result of years of bad management; while^ on the 

 other hand, a splendid pasture may owe more to good 

 farming than to the natural fertility of the soil. 



10. — Soils are usually arranged in four classes — clay, 

 sandy, calcareous, and organic soils — according to the 

 dominant ingredient. A soil consisting of nearly 

 equal parts of sand and clay is termed a loam ; 

 if two parts sand and one part clay, a sandi/ loam; 

 and if two parts clay and one part sand, & clay loam. 

 A soil consisting of nearly equal parts of clay and 

 lime is termed a marl ; if two of clay to one of 

 lime, it is a clay marl : and if two of lime to one 

 of clay, it i.s a calcareous marl. 



11,— The soils wbicb have their particlee iu th? 



