36 FIELD AND GARDEN PRODUCTS 



to the preparation of the seed bed for the alfalfa. Green-manure 

 crops are especially efficient in increasing the humus content of the 

 soil, and this is exactly what many soils require if alfalfa is to be 

 raised upon them. In the South cowpeas, crimson clover, vetches, 

 and even bur clover are successfully used. In the States farther 

 north crimson clover, cowpeas, soy beans, and vetches may be util- 

 ized. It is usually best to follow the green-manure crop with some 

 clean-culture crop before seeding the land to alfalfa, as the decaying 

 vines induce acid conditions in the soil that are unfavorable to the 

 alfalfa plants. (F. B. 192.) 



Commercial Fertilizers. If barnyard manure is not available 

 and if there is not time for the utilization of green-manure crops, it 

 is necessary to apply commercial fertilizer to any soil that may be 

 lacking in fertility. This fertilizer should be reasonably rich in 

 phosphoric acid and potash, but may be poor in nitrogen. However, 

 the kind and amount of fertilizer necessary vary greatly with the 

 soil and section, and exact recommendations can not be made. In 

 the humid sections of the country it is especially important to pro- 

 vide a well-drained soil for alfalfa. In the irrigated districts the 

 problem of drainage to prevent or reduce the accumulation of alkali 

 is often serious. In the regions of heavy rainfall natural drainage 

 must be provided. It has been found that alfalfa requires much 

 more complete drainage of the soil than do other field crops. Where 

 the underdrains are unable to carry off the rainfall rapidly enough, 

 it is sometimes the practice to backfurrow, leaving the dead furrows 

 at intervals of a rod or less. This permits the water to run off 

 quickly in the event of heavy rains. Alfalfa is often killed by over- 

 flows from streams. During its growing period it will not usually 

 withstand more than twenty-four hours of complete submergence or 

 more than forty-eight hours of partial overflow. During the dor- 

 mant period of winter, however, fields have been known to remain 

 under flowing water for two weeks without serious injury. 



A Well-Limed Soil Essential. No other forage crop requires 

 as much lime in the soil as does alfalfa. It is apparently necessary 

 that the soil acidity be neutralized by the lime and that there be 

 also an excess for the actual use of the plant. In one test an analysis 

 was made of the mineral constituents of certain crops. The per- 

 centage of lime in the alfalfa ash was 34.9, while red clover had but 

 20.6 per cent, and timothy had only 4.7 per cent. Throughout the 

 East and South alfalfa is most easily produced on the limestone soils. 

 Even these often require liming for the success of the alfalfa, as the 

 rains tend to leach the lime out of the surface layers of the soil. 



Weed-Free Soil. Young alfalfa plants are very tender and apt 

 to be killed by weeds during their early stages of growth. For this 

 reason it is essential that the land be as free from weeds as possible. 

 This condition can be brought about by raising some cultivated crop 

 for two or three seasons previous to planting alfalfa. The same re- 

 sults can also be secured by seeding the land successively to crops, 

 such as cowpeas, which naturally prevent the growth of weeds. If 

 a weedy soil must be used, the land should be plowed several months 



