256 ORCHARD MANAGEMENT 



Cover Crops. Most trees produce their new growth 

 from the time the buds open in the spring until midsummer. 

 It is therefore essential that the plant food be available 

 at this time. Plowing, harrowing, or disking the soil early 

 in the spring and keeping it well cultivated until midsum- 

 mer promotes this condition. To cease cultivation about 

 midsummer tends to stop the growth of wood and causes 

 it to ripen and harden for winter. The practice of sowing 

 some crop on the soil about midsummer to be later turned 

 under is called " cover cropping." 



Functions of Cover Crops. -- The relation of cover crops 

 to tree growth has already been explained. Their relation 

 to soil fertility is also important. A soil that is kept con- 

 stantly cultivated soon loses its humus and consequently 

 its mellowness and friability. To maintain the texture of 

 the soil, it is necessary to have plants decaying in it at all 

 times. When orchards are cultivated, this annual loss of 

 plant fiber to the soil must be replaced. The practice of 

 cover cropping generally proves to be the most economical 

 method. Under this system the soil grows its own crops, 

 produces its own humus, and thus maintains its own tex- 

 ture. When plants are plowed under in the spring, they 

 soon decay and the plant food that they contain is liberated 

 and becomes available at a time when the trees most need 

 this food. 



Light sandy soils and many of the clay soils are generally 

 low in nitrogen. Cover crops may be used to add nitrogen 

 to the soil. When a soil is low in nitrogen, those plants 

 that have the power of taking nitrogen from the air 

 should be sown. For this purpose clovers, vetches, peas, 

 and beans are sown. 



Cover crops prevent weed growth, and on sandy soils 



