MANURING AND WORN-OUT SOILS 331 



practicable to grow green manures between other 

 crops, or as a part of a definite system of rotation. 

 The rotations listed in the Appendix point out 

 many ways in which a green-manuring crop may 

 be grown without losing time. The effort should 

 be to have a "green crop" in the rotation every 

 few years, or at least a sod to plow under occasion- 

 ally; for there is humus and richness in a sod as 

 well as in a crop grown especially for plowing 

 under. 



Catch Crops and Cover Crops. There are two 

 ways of introducing a green -manuring crop for 

 part of a season. One is the use of a "catch crop," 

 which is grown during the season between the 

 time when one money-making crop is harvested 

 and another planted. Catch crops are used most 

 by market gardeners. 



Another way is to use a "cover crop," which is 

 sown late in the season after the main crop is out 

 of the way, so that it makes some growth in the 

 autumn, and perhaps in early spring also. A cover 

 crop not only adds humus to the soil but it also 

 protects the soil from heaving in spring. It catches 

 and holds the soluble plant food that would other- 

 wise be lost in seepage; this is returned to the soil 

 when the crop is plowed under in spring. It also 

 catches the snows and drys out the soil earlier in 

 spring. One of the commonest cover crops is rye 

 sown in corn or cotton at the last cultivation. 



Cover crops are now extensively used in fruit 

 growing. In addition to their other benefits, cover 

 crops in the orchard make the trees mature their 

 wood and fruit buds earlier in the fall and so lessen 

 danger of winter injury. There are hundreds of 

 ways in which a green-manuring crop may be intro- 

 duced, depending largely upon the system of 



