Soil Fertility 67 



under to add sufficient humus and nitrogen to improve mate- 

 rially the following cotton crop. It is the most economical 

 legume to use for this purpose, as when once a stand has been 

 secured and rows of the plants are left to seed it will volunteer 

 from year to year. The same method can be used with corn 

 or any other intertilled summer crop. There is some diffi- 

 culty in seeding bur clover in standing cotton, as in the harrow- 

 ing of the bur clover seed some of the ripe cotton is pulled out 

 of the bolls. On this account the harrowing should be done 

 just after the pickers have been through the field, to avoid as 

 far as possible any injury to the opened bolls." From Farm- 

 ers' Bulletin 693. 



Rye and buckwheat. Crops other than legumes are some- 

 times grown for green-manure. Rye is much used. It adds 

 no nitrogen, but it will grow on very poor soil, often on one 

 too poor to support a legume and as it makes a good growth of 

 stem it adds much humus-forming material to the soil. 



Buckwheat, in regions where it does well, is a good crop to 

 subdue new land. Its roots seem to break up the soil better 

 than those of most other crops. Usually the plants are 

 allowed to mature and are harvested, but often they are 

 plowed under as green-manure. Buckwheat is used in many 

 sections as a green-manure crop in orchards. 



FARM MANURE 



29. Importance of farm manure. The term farm manure 

 is used in this book to designate the solid and liquid voidings 

 of animals, together with the litter with which these voidings 

 are mixed. Barnyard manure, stable manure, animal manure, 

 and stall manure are other terms often used to designate this 

 product. Farm manure is the most important manurial re- 

 source of the farm; it contains fertility that has been drawn 

 from the soil and must be returned to it, if profitable crop pro- 

 duction is to be maintained. It not only benefits the soil by 

 returning nitrogen, phosphorus, and potassium, but it ren- 



