EFFECT OF IISfSECTS. — IMPROVEMENT OF THE SOIL. 323 



der it capable of being safely mixed with the surface soil. Unless, how- 

 ever, tliis ?nellowing be effected at once, and before admixture, a long 

 time may elapse ere the entire soil attain to its most perfect condition.* 



Again, it is known that some districts, for reasons perhaps not well un- 

 derstood, are more infested than others with insects that attack the corn 

 or other crops. These insects, their eggs, or their larvae, generally bury 

 themselves in the undisturbed soil, immediately beyond the ordinary 

 reach of the plough. If they remain wholly undisturbed during the 

 preparation of the soil, some species remain in a dormant state, and the 

 subsequent crop may in a great measure escape. Plough the land deep- 

 er than usual, and you bring them all to the surface. Do this in the 

 autumn, and leave your land unsown, and the frost of a severe winter 

 may kill the greater part, so that your crops may thereafter growin safety. 

 But cover them up again along with your winter corn, or let this 

 deep ploughing be done in the spring, and you bring all these insects 

 within reach of the early sun, and thus call them to life in such num- 

 bers as almost to ensure the destruction of your coming crop. It is to 

 something of this kind that I am inclined to attribute the immediate fail- 

 ures which have attended the trial of deep ploughing in certain parts of 

 England. Thus in Berkshire, certain soils which are usually ploughed 

 to a depth of only two inches, yielded almost nothing when deeper plough- 

 ing was more lately tried upon them — the crop was almost entirely de- 

 stroyed by insects. So also in the north of Yorkshire, where deep 

 ploughing has recently been attempted, the wheat crop on land so treated 

 was observed to sufler more from the worm than on any other spot. 

 Such facts as these, therefore, show the necessity of caution on the part 

 of the practical man, and especially of the land agent or steward, how- 

 ever correct may be the principles on which his general practice is 

 founded. Failures such as the above do not show the principle on which 

 deep ploughing is recommended to be false, or the practice to be in any 

 case reprehended : but it does show that a knowledge of natural local 

 peculiarities, and some study of ancient local practice, may, in an im- 

 portant degree, influence our mode of procedure in introducing more 

 improved methods of husbandry into any old agricultural district. 



§ C. Improvement of the soil by mixing. 

 There are some soils so obviously defective in constitution, that the 

 most common observer can at once pronounce them likely to be improved 

 by mechanical admixtures of various kinds. Thus peaty soils aboujid 

 too much in vegetable matter; a mixture of earthy substances, there- 

 fore, of almost any common kind, is readily indicated as a means of im- 

 provement. In like manner we naturally impart consistence to a sandy 



* Ttie Marquis of Tweedale, in his home-farm at Yeslers. has raised his land in value 

 eight times (horn 5s. to 40s. per acre), by draining and deep ploughing. After draining, the 

 fields of stiff clay, with streaks of sand in the subsoil, are turned over to a depth of 12 or 14 

 inches, by two ploughs (two hor.ses each) following one another, the under 6 inches being 

 thrown on the top. hi this state it is left to the winter's frost, when it falls to a yellow marly 

 looking soil Ii is now ploughed again to a depth of 9 or 10 inches, by which half the origi- 

 nal soil is lirought ajrain to the surface. By a cross ploughing this is mixed with the new 

 goil, after which the field is prepared in the usual way for turnips. But it is observed that if 

 the ploughing has been so late that the subsoil has not had a proper exposure to the winter's 

 cold, the land on such spots does not for many years equal that which was earlier ploughed. 

 The reason is, that when once mixed up with the other soil, the air has no longer the same 

 easy access ioto its pores. 



14* 



