152 MASS. EXPERIMENT STATION BULLETIN 154. 



Potash. — Alfalfa, in common with clovers and other legumes, 

 does well only when there is a liberal supply of potash in 

 available forms in the soil. Potash fertilizers should be freely 

 used in most cases in preparing for this crop. Potash in the 

 form of sulphate, in the writer's experiments, appears much 

 superior to potash applied in the form of muriate.^ 



PJiosphoric Acid. — Although usually relatively less deficient 

 in our soils as compared with the needs of alfalfa than lime 

 and potash, it should be applied in some form, and among 

 the different materials available basic slag meal seems usually 

 to prove best, no doubt because it contains a large proportion 

 of lime. 



Nitrogen. — A large amount of nitrogen in the soil is not 

 essential; from some points of view it is undesirable. To give 

 the crop a good start, a fair amount of this element in avail- 

 able form in the soil is essential, but beyond that it is un- 

 necessary and even harmful, — unnecessary because the alfalfa 

 can draw nitrogen from the air, and harmful because it 

 favors the grasses which may drive the alfalfa out. 



Varieties. 



There are a very large number of varieties of alfalfa now 

 known. Many which may prove valuable have recently been 

 introduced from Siberia by the South Dakota Experiment 

 Station, but these are as yet insufficiently tested. There are 

 but three kinds which deserve attention, known respectively 

 as the common,^ithe Grimm and the variegated. 



Common Alfalfa. — This appears to be simply an unnamed 

 strain. If from northern-grown seed, especially seed descended 

 from generations of alfalfa grown in the north, it is fairly 

 hardy and satisfactory. 



Grimm. — A specially selected strain which originated in 

 Minnesota; noted for hardiness and productiveness. It took 

 its name from the farmer said to have been one of the most 

 prominent in calling attention to the variety and promoting 

 its dissemination. Comparative trials at this station and in 

 many parts of the northern United States have indicated 



' See page 157. 



