SOIL. 





Chalk is iwrhsps the mineral must widely spread throughout 

 Britain. The chalk formation of itself forma a very poor and barren 

 oil. In the course of age* the surface of the chalk has been covered 

 with a thin coating of soil, consisting of chalk and organic matter 

 chiefly. On this soil the finest and most aromatic plants are found, 

 but of small dimensions, affording a sweet short pasture, much 

 relished by sheep. The constant treading in of the dung of the sheep, 

 and the stimulating effect of their urine, gradually increase the 

 quantity of vegetable and animal matter ; and thua the turf becomes 

 close and rich : but if this thin coat be disturbed by the plough and 

 mixed with the chalk below, it will, after one or two tolerable crops of 

 corn, be reduced to its original sterility; and it requires ages to 

 restore the fine pasture which once covered it. Such is the case with 

 those hills which are called the South Down Hills, in Sussex and Wilt- 

 shire, on which are bred the excellent sheep which bear that name. 



But the chalk has in many places been carried down by the rains 

 and transported in a comminuted state to the sandy or clayey valleys 

 around them, and by the mixture has greatly improved both, forming 

 various loams and marls in themselves highly fertile, or very useful in 

 increasing the fertility and texture of other soils. Chalk has the 

 peculiar property of neutralising acids of every description, and of 

 preventing their formation in the soil by the fermentation of vegetable 

 substances ; while it assists in that slow decomposition which causes 

 the evolution of carbonic acid, and thereby assists and invigorates 

 vegetation. The presence of carbonate of lime, if it does not exceed 

 a third part, and if it is intimately blended with alumina and silica, is 

 always a sign of fertility, especially when loose sand is mixed with it, 

 so as to form one-half of the whole soil. This is called a light 

 calcareous loam, and is usually found on the slopes or around the bam 

 of chalky hills. 



The Weald clay consists of very minute particles of alumina and 

 silica, forming a tough unctuous earth, fit for the growth of oaks, with 

 very few stones or visible particles. This soil is found in Sussex and 

 Kent chiefly. The plough cuts it into continuous slices, when it can 

 be ploughed, which is only in a certain state of moisture ; for when it 

 is dry the surface is as hard as a rock, while the subsoil is continually 

 moist, the water being unable to pass through its pores. It has the 

 most unpromising aspect, drying into hard lumps like brick, and appa- 

 rently incapable of being brought to such a state of mellowness as to 

 admit the seed or cause it to vegetate ; yet this stubborn soil may be 

 rendered fertile by tillage, draining, and exposure to frost in winter ; 

 and its tenacity may be corrected by the application of lime, ashes, 

 and other substances, especially fresh stable-dung, which interpose and 

 prevent the clods from re-uniting into one tough impervious mass. 

 Lime and chalk do this most effectually ; and when the weald clay has 

 been brought to a looser texture, it produces beans, wheat, oats, and 

 clover in great perfection. 



The system of complete under-draining by parallel draius, at the 

 distance of from 10 to 20 feet, which carries the moisture into the 

 Rurrounding ditched, has in many instances so greatly improved the 

 weald clays, that those who had formerly attempted to cultivate them 

 can scarcely believe their eyes when they see the abundant crops pro- 

 duced. Subsoil ploughing has also done wonders after complete 

 draining, in some cases rendering the soil so mellow and loose as to 

 allow of the cultivation of turnips, especially the Swedish. As clay 

 soils predominate in England, and their improvement has been almost 

 despaired of, it is of great importance that it should be generally known 

 that no soils repay the cost of improvement better than clays, provided 

 the surface be such as to admit of perfect draining. 



Another clay is called the Oxford clay. This is of a bluish colour, 

 which alters on exposure to the air, probably from a change in the 

 oxidation of the iron which it contains. This clay is favourable to the 

 growth of grass, and some of the richest pastures in Wiltshire and 

 Oxfordshire have it for a subsoil, over which the decomposition of the 

 roots and leaves of the grasses has formed a layer of vegetable mould 

 of the highest degree of fertility. In the fens of Lincolnshire, the 

 Oxford clay is covered by a coat of peat, formed by the decomposition 

 of aquatic plants, which have accumulated wherever the water hod no 

 natural exit. When these fens worn laid dry by an extensive system 

 of draining, the peat was converted into a rich soU by the admixture of 

 the clay which was found under it. 



The Oolite formation contains much carbonate of lime, cemented by 

 an unctuous earth into various sorts of stone. The soil which lies 

 over them, and which is of nearly the some nature, but broken and 

 disunited, is various in its qualities. Sometimes it is of great fertility, 

 and sometimes nearly barren, according as the impalpable matter in it 

 abounds and contains a duo proportion of the different earths, or it 

 resembles a loose chalky sand, in which moisture is retained with diili- 

 culty. In the first case, it produces every kind of grain in abundance 

 with moderate cultivation ; in the latter, it requires a great outlay of 

 manure, which readily disappears, and then it is justly called a ]>oor 

 hungry soil. 



On the red-sandstone is found a soil which is usually of the finest 

 quality. The fine loose soils of Devonshire and Somersetshire are of this 

 description. It unites most of the requisites of a good soil, both in ito 

 texture, neither too close nor too loose, and in the impalpable matter 

 in its composition. It is peculiarly adapted to the growth of potatoes 

 and all roots which form the basis of a judicious cultivation. When it 



contains a proper portion of calcareous earth, it may be reckoned 

 amongst the most fertile soils ; and where this is deficient, the 

 addition of lime or chalk is the beat means of improving it. The 

 calcareous earth seems greatly to add to the effect of the usual manures, 

 so that a much smaller portion is required to produce good crops. 



Each distinct formation gives rise to a great variety with respect to 

 fertility, even where the basis remains the same : but it is of groat 

 importance to the farmer to ascertain the general nature of the rocks 

 and strata on which his farm is incumbent. 



The alluvial soils formed by the deposit of a variety of earths in a 

 state of great division, and mixed with a considerable portion of 

 organic matter, form by far the most productive lands. They will 

 bear crop after crop with little or no addition of manure, and with a 

 very slight cultivation. These soils are found along the course of 

 rivers which traverse extensive plains, and which have such a current 

 as to keep very fine earth suspended by a gentle but constant agitation, 

 but not sufficiently rapid to carry along with it coarse gravel or sand. 

 Wherever there is an obstruction to the current and an eddy is formed, 

 there the soil is deposited in the form of mud, and gradually accumu- 

 lating, forms those alluvial soils which are so remarkable for their 

 fertility when carefully protected from the inroads of the waters. In 

 these soils the impalpable matter greatly predominates ; but the 

 intimate mixture of the earths with organic matter prevents their con- 

 solidating into a stiff clay ; and the gases which are continually i-volvi-d 

 from the organic matter keep the pores open, and give scope to the 

 growth as well as the nourishment of the roots. It is in the alluvial 

 soils principally that an accurate analysis is useful ; because the pro- 

 portion of their constituent parts varies in innumerable degrees. It 

 may be laid down as a general rule, that the most fertile of these soils 

 are those in which the earths are nearly in equal proportions, silica, 

 however, being the most abundant, with about 10 per cent, of organic 

 matter; a greater proportion of this last would form too loose and 

 spongy a soil to bear good crops of corn, especially of wheat. But 

 4 per cent, of vegetable matter, with a good mixture of earths, and 

 some phosphate of lime from the decomposition of bones and marine 

 shells, produces a very good wheat soil. The rich warp-lands along 

 the H umber are artificial alluvial soils, and although they contain but 

 a small proportion of organic matter, are highly fertile after their first 

 deposition, but it is observed that they gradually become more tena- 

 cious and difficult of cultivation as this humus is carried off by the 

 crops; and that it is soon necessary to add animal and vegetable 

 manures to supply its deficiency. 



Organic matter is no doubt essential to great fertility in a soil, but 

 some soils require more of it than others. In every stage of its spon- 

 taneous decomposition it keeps the pores of the soil open, and admits, 

 if it does not even attract, air and moisture to the fibres of the roots. 

 In all rich soils which have been long cultivated, especially in g;u 

 there are particles of a dork colour and fibrous texture, which in the 

 microscope appear like minute logs of charred wood. These keep the 

 soil open, and supply carbonic acid, when the air reaches them. A 

 proper texture seems an indispensable condition of fertility. It is 

 much easier to supply the deficiency of vegetable matter in a 

 soil, which at best forms but a very small portion of it, than 

 of silica or clay, which should enter into its composition in the 

 proportion of one half or a third of the whole. It is practicable to 

 carry lime or chalk upon soils which do not contain calcareous matter ; 

 clay may also be carried upon loose sandy soils, where it can be found 

 below the surface, or at a moderate distance ; but if a soil is very 

 deficient in silica, it requires so large a proportion of this earth to 

 give porosity to stiff clay, that it very seldom can repay the trouble 

 and expense. Hence the difficulty of bringing poor wet clay soils into 

 a [fertile state, except where an abundance of chalk and vegetable 

 manures can be easily procured. In this case the perfect draining of 

 the land, and exposure of the ploughed surface to the frosta of winter, 

 with the addition of chalk and manure, produce such an alteration in 

 the texture of the clay, that by continuing the improving process it is 

 entirely changed into a mellow and fertile loam. The burning of a 

 portion of the retentive subsoil into a brick-like earth giv< 

 porosity which renders it mechanically similar to silicious sand, and 

 converting the iron which all these clays contain into a peroxide, the 

 soil is thereby greatly improved in fertility ; for it seems that iron, in 

 a state of slight oxidation, or combined with any acid, is hurtful to 

 vegetation, whereas the red peroxide is not only innocuous, but seems 

 to have fertilising properties. 



In ascertaining the value of a soil for the purposes of agriculture, two 

 circumstances should be carefully noticed. The first is the | 

 bility of the soil to water ; and the second is its power of absorbing 

 moisture from the atmosphere. To ascertain the first, it is only 

 required to place an equal weight of different soils in glass tubes of 

 equal diameter, pressing them so that they shall occupy equal spaces, 

 but not filling the tubes. Then pour an equal quantity of water over 

 each soil, and place them upright with cups under them. Examine 

 which has the surface first dry, and how much water runs through 

 each in a given time. That which presents a dry surf.u <, while it 

 holds most water in its pores, is probably the best. To ascertain the 

 comparative absorption of moisture, the soils are dried in pairs on a plate 

 of metal heated by steam, or at a heat of 212", to expel the water. 

 They are then placed in equal quantities in similar flat cups or dishes, 



