410 ROTATION OF CROPS. 



3. Plants which draw a great deal of nourishment from the soil 

 should succeed, or be succeeded by, plants which draw less nourish- 

 ment. Hence a crop grown for its fruit, such as the pea ; or for its 

 roots or bulbs, such as the potato or the onion, should be followed by 

 such as are grown solely for their leaves, such as the common borecole, 

 the celery, the lettuce, &c. 



4. Plants which remain for several years on the soil, such as straw- 

 berries, rhubarb, asparagus, &c., should not be succeeded by other 

 plants which remain a long time on the soil, but by crops of short 

 duration ; and the soil should be continued under such crops for as 

 long a period as it remained under a permanent crop. Hence, in 

 judiciously cropped gardens, the strawberry compartment is changed 

 every three or four years, till it has gone the circuit of all the com- 

 partments ; and asparagus beds, sea-kale, &c., are renewed on the same 

 principles. 



5. Plants, the produce of which is collected during summer, should 

 be succeeded by those of which the produce is chiefly gathered in 

 winter or spring. The object of this rule is to prevent two exhausting 

 crops from following each other in succession. 



6. Plants in gardens are sometimes allowed to ripen their seeds, in 

 which case two seed-bearing crops should not follow each other in 

 succession. 



These rules, and others of a like kind, apply generally to both sys- 

 tems of the successional crops, and they are independent altogether of 

 other rules or principles which may be drawn from the nature of the 

 plants themselves, such as some requiring an extraordinary proportion 

 of air, light, shade, moisture, time, &c., or from the nature of the 

 changes intended to be made on them by cultivation, such as blanch- 

 ing, increase of succulency, magnitude, &c. We shall now notice the 

 two systems separately. 



Successional Cropping. The plants calculated for this mode of crop- 

 ping are such as require, during almost every period of their growth, 

 the fullest exposure to light and air, and remain a considerable time in 

 the soil : these are, the turnip, the onion, the potato, the carrot, &c. If 

 any of these crops are raised and brought forward under the shade of 

 others, they will be materially injured both in quality and quantity; 

 though at the same time, while they are merely germinating, shade will 

 not injure them. Hence successional cropping may be carried on in 

 breadths of twenty or thirty feet between rows of tall-growing plants 

 without injury, thus approximating this manner of cropping to the 

 simultaneous mode, which, wherever the soil is rich, is by far the most 

 profitable. 



The simultaneous mode of cropping is founded on the principles that 

 most plants, when germinating, and for some time afterwards, thrive 

 best in the shade; and that tall-growing plants, which require to 

 receive the light on each side, should be sown or planted at some dis- 

 tance from each other. Hence, tall-growing peas are sown in rows 

 ten, twelve, or twenty feet apart, and between them are planted rows 

 of the cabbage tribe; and again, between these are sown rows of 



