20 MEADOWS AND PASTURES 



suppressed. When the grasses have again exhausted part 

 of the available nitrogen and become less vigorous the 

 clover reappears, and so the endless round of nature goes 

 on. Timothy yields much more hay when red clover is 

 sown with it than when sown alone; Bermuda grass 

 thrives best when white or bur clover is grown with it, 

 for any clover will secure nitrogen from the air. 



AN OLD SOD IS RICH. 



"To break a pasture will make a man, to make a pas- 

 ture will break a man," is an old English saying. It is 

 well known that sod ground is rich, especially rich in 

 nitrogen. Grasses will not yield their maximum till they 

 have accumulated a "sod." What is a sod? It is a tough 

 fibrous mass of roots, stems and decaying leaves; half is 

 alive and half is dead. It is made up of all the plants 

 that grow on the pasture grasses, clovers and weeds. 

 It may be as tough almost as a carpet, and can be cut and 

 rolled like a green rug. Sods contain much nitrogen. 

 How do they get it ? It was not till 1901 that we knew of 

 a group of beneficent bacteria that live on decaying veg- 

 etable matter in the soil, the "azotobacter." This group 

 of bacteria revels in old pasture sods ; the bacteria like a 

 soil rich in decaying vegetation, with enough lime, with 

 air in plenty and moisture enough. It is through these 

 azotobacter that old sods, even when clovers have been 

 absent, are yet rich in nitrogen. 



PRODUCTIVITY OF PASTURES. 



Old sods often have double the carrying power of new- 

 ly-seeded grass land. The reasons for this may be va- 

 rious, yet one chief reason is in the presence in the old 



