50 



The Country Gentleman's Magazine 



that the air we breathe is a powerful manure. 

 So it is, but not in the same sense that stable 

 dung or guano is a powerful manure. The 

 air may and does afford to plants much of 

 their food, but it can only help them to the 

 minerals they require by dissolving them oilt 

 of pebbles, flints, nodules of chalk, sand- 

 stone, and other substances in the soil which 

 contain them in what we may term a locked- 

 up condition. The importance of frequent 

 and deep stirrings of the soil is seen in this, 

 that every fresh surface exposed to the air, 

 and especially to frost and snow, is as the 

 opening of a new mine of minerals for the 

 service of those plants on which man 

 depends for his subsistence. 



The application to practice of these consi- 

 derations is an extremely simple matter in 

 the first instance, but it may become very 

 complicated before we have done with it. 

 Here, indeed, we can only touch the surface 

 of the subject, yet we hope to do so usefully. 

 Suppose that we grow Cabbage, or Cauliflower, 

 or Brocoli, on the same plot of ground, one 

 crop following the other as rapidly as possi- 

 ble for a long series of years, and take care 

 never to refresh the soil with a scrap of man- 

 ure. It must be evident that we shall, some 

 day or other, find the crop fail through the 

 exhaustion of the soil of its available sulphur, 

 soda, phosphates, lime, and potash. But if 

 this soil were allowed to lie fallow for some 

 time, it would again produce a crop of Cab- 

 bage, owing to the liberation from the locked- 

 up state of mineral matters which, when the 

 crops were failing, were not hberated fast 

 enough, but owing to the rest allowed the 

 soil, have at last accumulated sufficiently to 

 sustain a crop. Now the reader will perceive 

 that this mode of procedure is unprofitable, 

 to begin with, and tends of necessity to utter 

 exhaustion of the soil, although we must con- 

 fess that utter exhaustion of any soil is a 

 thing at present unknown. However, in- 

 stead of following an exhaustive practice, we 

 enrich the soil with manure, and change the 

 crops on the same plot, so that when one 

 crop has largely taxed it for one class of 

 minerals, another crop is put on which will 

 tax it for another class of minerals. Let us 



take for a moment's consideration one of the 

 necessary constitutents of a fertile soil, com- 

 mon salt. In the ash of a Cabbage there is 

 about 5 or 6 per cent, of this mineral, in the 

 Turnip about lo per cent., in the Potato 2 to 

 3 per cent., in the Mangold or Beet 20 to 40 

 per cent. On the other hand, the Mangold or 

 Beet is almost destitute of sulphur and phos- 

 phates, but they both agree in being strongly 

 charged with potash and soda. Now, it fol- 

 lows that if we crop a piece of ground with 

 Cabbage, and wish to avoid the failure that 

 may occur if we continue to crop with 

 Cabbage, we may expect to do well by 

 giving the ground a dressing of common salt 

 and alkalies, and then crop it with Beets or 

 Mangolds. 



The whole subject is not exhausted by this 

 mode of viewing it, for, in the first place, the 

 whole subject is not yet fully understood by 

 the ablest of our chemists and physiologists^ 

 and, in the next place, crops differ in their 

 modes of seeking nourishment, and we might 

 find two distinct plants nearly agreeing in 

 chemical constitution, and yet one might fail 

 where the other would succeed. Suppose^ 

 for instance, we have grown Cabbage and 

 other surface rooting crops until the soil 

 begins to fail, even then we might obtain from 

 it a good crop of Parsnips or Carrots, for 

 the simple reason that these send their roots 

 down to a stratum that the Cabbage never 

 reached, and it is most instructive to bear in 

 mind that although the Parsnip will grow- 

 well on poor land, and pay well on land that 

 has been badly tilled for years, yet the ashes 

 of the Parsnip contain 36 per cent, of 

 potash, II per cent, of lime, 18 per cent, of 

 phosphoric acid, 6 per cent, of sulphuric 

 acid, 3 per cent, of phosphate of iron, and 5 

 per cent, of common salt. How does the 

 Parsnip obtain its mineral food in an ex- 

 hausted soil ? Simply by pushing down for it 

 into a mine that has been but little worked, 

 though the Cabbage might fail on the same 

 plot through trusting to the over-worked 

 superficial stratum. 



Having attempted a general, we now pro- 

 ceed to a particular application. In the 

 first place, it is proper to say that good land. 



