18 MARKET GARDENING 



able and desirahle sources of humus, but the rotting of green 

 crops when ploughed under has a tendency to leave the soil 

 somewhat acid. Before attempting to grow all kinds of 

 vegetables in soil on which a green crop has been grown 

 and ploughed under, an application of lime must be made 

 to neutralize the acidity. 



27. Catch Crops. Green crops arc often grown as catch 

 crops. After the ground is cleared in the fall, or even before 

 the crop is off the ground, a sowing may be made of crimson 

 clover or rj'e. Crimson clover is often sowed between the 

 rows of sweet corn when the last cultivation is given. Such 

 catch crops may be grown as sources of humus, or as is often 

 the case, they are grown to hold the soil and to prevent 

 washing. Catch crops being grown only through a limited 

 season seldom grow to much size. 



