ALFALFA. 155 



It is possible, by the use of a harrow at the proper season, 

 to in a measure check the coming in of grasses and clovers. 

 These are more shallow rooted than alfalfa and may, therefore, 

 be uprooted without much injuring the latter. A spring-tooth 

 harrow properly set is the most effective type, and a special 

 form of tooth has been designed for this particular use. This 

 implement is advertised as the alfalfa harrow. Its use is most 

 effective when the soil is relatively dry, and immediately after 

 cutting either the first or the second crop will usually prove 

 the best time for the operation. 



Winterkilling. — Any one of the following causes may, 

 under unfavorable conditions, destroy alfalfa : — 



1. Heaving, which is most serious on the heavy soils. 

 Tendency to this is much reduced by allowing a relatively 

 heavy growth to remain in the field for winter protection. 

 Perfect underdrainage, natural or artificial, of course lessens 

 the tendency to heave, which is greater in proportion as the 

 water content of the soil increases.^ 



2. Formation of ice on the surface. This is something 

 which, under extreme weather conditions, may affect any 

 field, but the tendency to this injury is comparatively small 

 in fields where the slopes are such as to rapidly carry off 

 surface water. 



3. The presence of free acid in the soil, for this weakens 

 the plant, rendering it susceptible to unfavorable conditions 

 of any kind. The remedy is of course the application of lime. 



4. Insufficient winter protection, due to too late cutting or 

 excessive or overlate pasturing. 



Recent Experimental Work with Alfalfa at this 



Station. 

 The more important of the recent experiments with alfalfa 

 in this station have been as follows : — 



1. Comparison of Grimm with the common alfalfa. 



2. Comparison of high-grade sulphate with muriate as a 

 source of potash. 



' Much alfalfa was killed during the year of 1913-14. The cause is not surely known; but it 

 seems possible it was due in a measure to the large amount of water in the soil, owing to heavy 

 fall and early winter rains (see p. 170). 



