Circular No. 55 (Revision of No. 37). August, 1915. 



MASSACHUSETTS AGRICULTURAL EXPERIMENT STATION. 



AMHERST. 



GREEN MANURING AND COVER CROPS. 

 By William P. Brooks. 



Green manuring is the practice of cultivating a crop for soil 

 improvement. The crop is usually, but not always, plowed in 

 while green. A cover crop is one grown largely for soil protection, 

 but it may at the same time serve all the purposes of a green manure 

 crop. On the other hand, during the period of its growth a green 

 manure crop is a cover crop. 



The practice of using crops for soil protection and improvement 

 has received much more attention in recent years than formerly, 

 largely because its possible benefits and the conditions essential 

 to their realization are better understood. It is not yet as general 

 as it should be. The objects of this circular are: 



1. To briefly indicate the possible benefits from the use of 

 green manure and cover crops, and the principal reasons therefor. 



2. To consider the special characteristics, value and adaptation 

 of each of the principal crops. 



3. To state the conditions under which the introduction of these 

 crops is to be advised. 



I. POSSIBLE BENEFITS 



The protection of the soil against damage by 

 Erosion prevented, wind which carries away the finer and better 

 particles, and water which washes fields which 

 have any considerable slope. In other words, to prevent erosion. 



The conservation of soluble plant-food com- 

 Plant-food saved, pounds. Plant-food compounds soluble in 



water tend to wash through the soil (and of 

 course most largely on those which are of coarse and open texture) 

 to lower levels, or they are carried away through natural or artificial 

 drainage channels. The danger of this loss is of course greatest 

 in seasons of abundant rainfall and it goes on most largely in fields 

 which are bare. If the soil be kept full of hungry rootlets of a 

 growing crop the amount of loss through this source is greatly 

 reduced. 



Green manure and cover crops may be made 

 Weeds prevented, of much use in preventing the growth of 



weeds and the ripening of weed seeds, and 

 also in some cases they may be made very helpful in exterminating 

 certain kinds of weeds with which a field may have become infested. 



