Rotation of Crops in Vegetable-Gardening 31 



stituted for the fall Irish potatoes, we would have a com- 

 plete four-crop rotation. 



A rotation should, as a rule, include a crop of some 

 legume. This will keep the soil in good condition and 

 add to the amount of nitrogen. Otherwise, more nitrogen 

 must be applied, as manure or fertilizer. Legumes used 

 in Florida in a rotation are velvet beans, beggarweed, 

 peanuts, and cowpeas. In other subtropical regions, as 

 Egypt, the broad bean is used as a winter forage crop. 

 In tropical countries, however, the pigeon pea, green gram 

 or woolly pyrol, the jack bean or sword bean, and others 

 are used in rotations. 



COVER-CROPS, OR PLANTS USED TO PROTECT AND ENRICH 

 SOIL 



The rain that falls on the land during the year leaches 

 out much soluble plant-food or fertilizer, unless there is 

 some way of holding it in the soil. Fertilizer must be in a 

 soluble condition before plants can appropriate it. If there 

 are no plants present to appropriate the soluble part of 

 the fertilizer, it is evident that the rain will carry this por- 

 tion out of the soil into the waterways ; but if plants use 

 it at once when it becomes available, it remains on the 

 land. When these plants decay, they return this stored-up 

 food, and also humus, to the soil. 



Plants as a source of nitrogen. 



The primary source of nitrogen is the air. Nitrogen 

 enters plants in different ways; most vegetables take it 

 up from the soil, but a few are known to take it from the 



