PASTURES, MEADOWS, AND FORAGE 183 



since the clovers are host plants to the grasses. 

 They start early and protect the later-growing 

 grasses. Most of the clovers live but from one 

 to three years. The clovers, in common with 

 other legumes, contain a large percentage of 

 potential nitrogen (110, 138, 190). The pasture 

 grasses are much benefited by a full supply of 

 nitrogen, but they can secure little, if any, from 

 the air, and hence must supply their needs as 

 best they can from that found in the soil. It 

 will then be understood how eagerly the hungry 

 grasses feed on the decaying short-lived clovers. 

 It will also be understood why clovers are called 

 host plants. 



313. The short-lived host plants may be per- 

 petuated, and the grasses kept young and vig- 

 orous, by sowing seeds of the clovers and 

 grasses every two or three years in early spring, 

 and scarifying the surface with a sharp-toothed 

 harrow, this to be followed by the roller. The 

 harrowing will not only tear out some of the 

 superannuated grass roots (270) and old plants 

 and cover the seeds, but it will tend to aerate the 

 surface soil and to promote bacterial activity. 

 From time to time, a light dressing of farm 

 manures or of commercial fertilizers should be 

 applied, spread evenly, in the fall. 



314. An inspection of the field should be 

 made each spring, in order that seed may be 



