THE DECOMPOSITION OF SWEET CLOVER (MELILOTUS 



ALBA DESR.) AS A GREEN MANURE UNDER 



GREENHOUSE CONDITIONS i 



L. A. Maynard 



The practice of green-manuring as a method of restoring and main- 

 taining soil fertility has become more and more general as evidence 

 regarding its value has accumulated and methods of procedure have been 

 worked out. The choice of a green manure best suited to given conditions 

 has been a subject of much investigation. The literature of the subject 

 abounds with data regarding alfalfa, crimson clover, and various other 

 plants that gather nitrogen from the air. 



A plant of this type to which little attention has been given is sweet 

 clover. This has long been regarded as a weed because of its occurrence 

 in waste places, its general rank growth, and its ability to thrive under 

 conditions unfavorable for the development of other plants. The fact 

 seems to have been overlooked that these very characteristics, coupled 

 with nitrogen-gathering power, are the features desired in a soil renovator. 

 Recently several writers have called attention to the possibilities of sweet 

 clover for this purpose, but experimental data are lacking. The present 

 investigation is a study of the ability of the plant to gather nitrogen, 

 and the rate with which this nitrogen becomes available when the plant 

 material is incorporated with the soil. 



Sweet clover obtains its name from the peculiar sweetish fragrance 

 of its flowers, due to an ethereal oil, coumarin. The plant is known by 

 a variety of other names, such as Melilotus, Bokhara, giant clover, and 

 wild alfalfa. Three species are common in the United States — the 

 white biennial {Melilotus alba Desr.), the large yellow biennial {Melilotus 

 officinalis Lam.), and the small yellow annual {Melilotus indica All.). 

 This investigation concerns itself with the first species, which is commonly 

 referred to as Bokhara, or merely as sweet clover. The name Bokhara is 

 obtained from a district in Asiatic Russia, supposedly the original home 

 of the plant. 



Sweet clover is an erect, stemmy plant, reaching a height of from 

 eighteen to thirty inches the first year; a single plant growing by itself 

 will tend to branch more than do plants growing together. When young 

 the plant resembles alfalfa, but its leaves are usually more broadly ovate 

 and its foliage is less dense. At bloom it is easily recognized by its 



1 The work described in this bulletin was done in the Department of Agricultural Chemistry, under 

 the direction of Professor George W. Cavanaugh. 



