190 THE ROTATION OF CROPS 



on the same plot through trusting to the overworked superficial 

 stratum. 



Having attempted a general, we now proceed to a particular appli- 

 cation. In the first place, it is proper to say that good land, well 

 tilled and abundantly manured, cannot be soon exhausted ; but even 

 in this case a rotation of crops is advisable. It is less easy to say 

 why, than to insist that in practice we find it so. The question then 

 arises What is a rotation of crops ? It is the ordering of a succes- 

 sion in such a manner that they will successively tax the soil for 

 mineral aliments in a different manner. A good rotation will include 

 both chemical and mechanical differences, and place tap-roots in a 

 course between surface roots, as, for example, Carrots, Parsnips, and 

 Beets, after Cabbage, Cauliflower, and Broccoli and light, quick 

 surface crops, such as Spinach, to serve as substitutes for fallows. 

 The cropping of the kitchen garden should be, as far as possible, 

 so ordered that plants of the same natural families never succeed one 

 another ; and, above all things, it is important to shift from place to 

 place, year after year, all the Cabbage and the Potatoes, because these 

 are the most exhaustive crops we grow. In a ton of Potatoes there 

 are about twelve pounds of potash, four pounds of sulphuric acid, 

 four pounds of phosphoric acid, and one pound of magnesia. We 

 may replace these substances by abundant manuring, and we are 

 bound to say that the best rotation will not obviate the necessity for 

 manuring ; but even then it is well to crop the plot with Peas, 

 Spinach, Lettuce, and other plants that occupy it for a comparatively 

 brief space of time, and necessitate much digging and stirring ; for 

 these mechanical agencies combine with the manure in preparing the 

 plot to grow Potatoes again much better than if the land were kept 

 to this crop only from year to year. If we could mark out a plot of 

 ground into four parts, we should devote one plot to permanent 

 crops such as Asparagus, Sea Kale, and Rhubarb and on the other 

 three keep the crops revolving in some such order as this : No. i, 

 short-lived crops, such as Peas, Spinach, and saladings, to be followed 

 by Cabbage ; No. 2, tap-roots, such as Carrots, Parsnips, and Beets ; 

 No. 3, Potatoes, Turnips, and Onions. In the next season the 

 original No. 2 would be cropped as the original No. i, and the 

 original No. 3 as No. 2, In the next year the original No. 3 would 

 be cropped as the original No. i ; and so on : every crop to be pre- 

 pared for by vigorous stirring of the ground and liberal manuring ; 

 and if the subsoil were good, we should trench it two spits deep for 

 every root crop. 



