AGRICULTURAL TEXT-BOOK. 69 



has become by cultivation deficient in soluble lime and sulphuric acid, 

 two constituents consumed iu large quantities by clover ; and which 

 must be supplied before clover can grow. The clover is therefore sown 

 with powdered plaster which contains these two elements, and it grows 

 luxuriantly. But while the surface soil has been impoverished, the sub 

 soil remains full of salts ; and the clover sends down its deep tap roots 

 into the subsoil, collects such inorganic matter as its finds there, and 

 brings it to the surface. The sheep eat the green part, and scatter the con 

 stituents of the clover over the ground, together Kith theammonia formed 

 in the urine. The clover is then plowed up, and all that it has received 

 from the subsoil and the air, is again rendered more or less soluble by 

 decay, and supplied to the surface soil where the wheat roots find it. 

 This can scarcely be called real manuring. With the exception of a lit 

 tle lime and sulphuric acid, nothing is supplied to the field but what it 

 or the air contained before. The clover has acted as a collector. It has 

 brought together on the surface what was before scattered in the sub 

 soil, but it affords nothing new. The effect, in time, of such practice 

 must be, that not only the surface but the subsoil also becomes impov 

 erished ; and each crop of wheat carries off the constituents of a larger 

 area, than it could possibly do without clover. Unless, manures from 

 the barn-yard or other sources are also supplied, the soil must, finally, 

 be very serously injured. 



180. There are various modes of preparing the land for 

 Wheat; (a,) summer following, with three distinct plowings, 

 (b J plow ing once ; (c,) plowing once and rendering the surface 

 mellow with a cultivator; all of which have their advocates, 

 and all are probably good for peculiar soils, and under peculiar 

 circumstances. (See PLOWING.) 



181. There are also various modes of covering the grain, (a,) 

 by a harrow or drag; (b,) by plowing it in with a shallow fur 

 row with a plow or cultivator; (c,) by ribbing; (d,) with a 

 Drill Machine. (See IMPLEMENTS.) 



182. Wheat is sown (a,) either broadcast by hand or by a 

 machine ; (b,) by a drill ; or in England (c,) by a dibble. 



183. It is harvested (a,) by hand with a sickle or reaping- 

 hook ; (b,) with a cradle ; (c,) by a machine worked by horses. 



