BESTORING FERTILITY TO THE SOIL. 337 



in the size of the Indian corn crops, as compared with the 

 wheat crops in the States, is partly accounted for by their 

 greater freedom from weeds, which are large consumers of 

 nitric acid, and, in the case of the wheat crop, frequently re- 

 duce the yield by several bushels per acre. It must, however, 

 be borne in mind that, though the wheat is robbed of its food 

 where there are weeds, still if there were no weeds, the amount 

 of nitric acid which the crop could not get hold of, would, in 

 all probabilty, be washed out of the soil during the ensuing 

 winter. I come to the conclusion, therefore, that the nitro- 

 gen alone, which would be required to produce one bushel of 

 wheat, would cost not much less than fifty cents ; and that, in 

 consequence, wheat-growing by means of artificial manures, 

 will not pay upon very poor land. 



I have said that the land, about which I was consulted, had 

 not been plowed for several years, and that although nature 

 had done all she could to clothe the soil with vegetation, the 

 most disheartening feature in the case was, the poverty of the 

 weeds. A thistle may be a giant or a dwarf, according to cir- 

 cumstances ; here they were all dwarfs. The plaintain, which 

 I believe is sometimes sown in these districts for. food, has a 

 very deep root ; here the plants were abundant, but the leaves 

 were very small and lay so close to the ground, that, as the 

 manager informed me, " the sheep were often injured from the 

 amount of sand which they swallowed with the leaves when 

 feeding." 



At Rothamsted, the analyses of the rain water passing 

 through the ordinary soil of one of my fields, which has been 

 kept free from vegetation, have shown that the amount of 

 nitric acid liberated in a soil, and washed ou^ each year, is very 

 large. Taking the ten years during which these special experi- 

 ments have been in progress, I should think that the loss of 

 nitrogen would be equal to, or possibly exceed, the amount of 

 that substance removed by the average crops grown in the 

 United States. 



The results obtained by the rain gauges, are further com- 

 pletely confirmed by those in an adjoining field, where wheat 

 and fallow have been grown alternately for twenty-seven years. 

 The liberation of nitric acid, during the year of rest, produced 

 for a time a large growth of wheat, but it was done at a very 

 great waste of the fertility of the soil, and ihe produce is now, 

 in proportion, considerably lower than ihafc growD ou the con- 

 tinuously unman ured land. 

 15 



