CLOVERS AND OTHER LEGUMES 259 



dust. It may be applied with a special machine made 

 for this purpose, or with a manure spreader, the crushed 

 stone being put on top of a layer of manure. 



If the soil is only shghtly acid, from two to three tons 

 per acre are applied ; if it is strongly acid, the appUcation 

 should be increased to five or six tons, or even more, as 

 no harm results from using more than is necessary. The 

 only rehable way to determine the amount required is 

 to make trial of the different rates of application. It 

 should be disced or harrowed into the surface soil but not 

 plowed under. 



If crushed hmestone can not be procured, lime of any 

 kind may be used. In such case, the apphcation may be 

 not more than half as great as if limestone were used; 

 and, except in the case of air slaked lime, it should not 

 be allowed to come into contact with plants, as injury may 

 result. 



197. How to add Humus and Phosphorus to the Soil. — 



In soils that have long been cultivated without a careful 

 system of rotation, humus is deficient ; and unless phos- 

 phorus has been appUed to the soil, it is probably lacking 

 also. Humus may be added to the land by plowing under 

 green crops; or both humus and phosphorus may be 

 added to it by the application of barnyard manure. If the 

 latter is used, it is advisable to apply with it pulverized 

 rock phosphate, or floats. 



At least ten tons of manure should be applied to each acre 

 and not less than five hundred pounds per acre of floats. 



198. How Bacteria are added to the Soil. — The soil 

 from a field in which any clover is estabUshed and thriving, 

 contains very many of the bacteria which are necessary 

 to that crop. 



