376 FORAGE PLANTS AND THEIR CULTURE 



plots which received acid phosphate or a mixture of acid 

 phosphate and potash salts the growth of clover predomi- 

 nated more and more as the season advanced. On the 

 other hand, where the nitrate of soda was used alone or 

 in a mixture with acid phosphate and potash the orchard- 

 grass predominated; that is, the minerals enabled the 

 clover to crowd the grass, while the nitrate of soda enabled 

 the grass to crowd the clover." 



440. Gypsum. Gypsum was formerly much used for 

 its favorable effect on clover, but in the United States 

 now seems to be employed only in western Oregon. At 

 the Oregon Experiment Station, increases in yield of from 

 20 to 200 per cent were secured. The rate of application 

 varies from 40 to 200 pounds to an acre. 



The cessation of the use of this substance in the East- 

 ern States is perhaps largely the result of the increased 

 use of lime. There is difference of opinion as to the 

 action of gypsum, but it is generally agreed that it is in- 

 effective on poor land. 



441. Lime. Lime has in general given an increased 

 yield when applied to the soil before sowing red clover. 

 Usual applications are 1000 to 2000 pounds of burned 

 lime or twice as much of ground limestone to an acre. 



Most investigators regard the litmus test as a fairly 

 reliable indication that the soil needs lime, but in some 

 cases this does not hold true. For example, at the Ohio 

 Experiment Station clover grew normally on one soil and 

 but poorly on two others, all of which reddened litmus 

 paper. Lime alone did not benefit the first soil for 

 clover but improved the crop on the last two, though it 

 did not bring about a full yield. 



442. Irrigation. Clover is not much grown on irrigated 

 lands, principally because alfalfa will yield far larger 



