ROTATION OF CROPS. 



437 



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 strawberries, 

 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 straw- 

 berry compartment is changed every three or four years, till it has gone the 

 circuit of all the compartments; 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 fol- 

 lowing 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 systems of 

 the successional crops ; and tliey 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, lighty shade, 

 moisture, &c. : or from the nature of the changes intended to be made 

 on them by cultivation, such as blanching, succulency, magnitude, &c. We 

 shall now notice the two systems separately. 



920. 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 the 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 

 20 or 30 feet, between rows of tall-growing articles, without injury ; which 

 approximates this manner of cropping to the simultaneous mode, which, 

 wherever the soil is rich, is by far the most profitable. 



921. The simultaneous mode- of cropping is founded on the prmciples 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 distance from each other. 

 Hence, tall-growing peas are sown in rows 1 0 or 12 feet apai-t ; and between 

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

 sown rows of spinach, lettuce, or radishes, &c. Hence, also, beans are planted 

 in the same rows with cabbages (an old practice in the cottage gardens of 

 Scotland), and so on. The great object, in this kind of cropping, is to have 

 crops on the ground in different stages of growth ; so that, the moment the 

 soil and the surface are released from one crop, another may be in an advanced 

 state, and ready, as it were, to supply its place. For this purpose, when- 

 ever one crop is removed, its place ought to be instantly supplied by plants 

 adapted for producing another crop of the proper nature to succeed it. For 

 example, where rows of tall marrow-fat peas have rows of broccoli between 

 them, then the moment the peas are removed, a trench for celery may 

 be formed where each row of peas stood ; and between the rows of broccoli 



