Part II.] MAINTENANCE OF SOIL FERTILITY. 43 



yard manure. Part of this increase is no doubt due to the 

 secondary effect on corn of the largely increased clover crops, 

 but a very considerable gain became manifest from the first 

 application of the lime and before the clover had had oppor- 

 tunity to produce its effect. Moreover, the great corn lands 

 are those well supplied with lime. 



Oats has shown the least effect, varying from nothing on the 

 land receiving a complete fertilizer, with nitrate of soda as the 

 carrier of nitrogen, to 18 per cent on the unfertilized land. 



Wheat has been increased by 8 to 10 per cent after the 

 complete fertilizer and manure, and 27 per cent on the un- 

 fertilized land. 



Clover has shown the greatest increase, the gain in yield 

 of hay ranging from 27 per cent on the manured land to 44 

 per cent on the unfertilized land and that treated with acid 

 phosphate. These figures do not tell the whole story respect- 

 ing the clover crop, however, for a large proportion of the hay 

 on the unlimed land has consisted of sorrel, plantain and other 

 weeds. 



Timothy, the fifth crop in the rotation, has shared in the 

 general prosperity, giving a yield 12 to 25 per cent greater on 

 the limed than on the unlimed land. 



It seems probable that the relatively low effect of the liming 

 on the oats crop is due to the management of the land. The 

 lime is applied to the surface after plowing for corn, and har- 

 rowed in. The corn stubble is plowed under for oats, thus 

 burying much of the lime below the reach of the oat roots. The 

 oat stubble is plowed for wheat, bringing the lime to the sur- 

 face again, where it is in the best situation to benefit the 

 clover and timothy which are seeded on the wheat in the spring. 



Lime performs a double function in the soil. In the first 

 place, its two mineral constituents, calcium and magnesium, 

 are included in the small list of those elements which are in- 

 dispensable to the living organism. Every living cell, whether 

 of plant or animal, contains these elements. For this purpose 

 we would not need to use lime in any larger quantity than we 

 use other fertilizing materials; in fact, our ordinary phos- 

 phates, which are combinations of phosphorus with calcium, 

 would contain enough calcium, at least for most conditions. 



