4 N, H. AGR. EXPERIMENT STATION. [Bulletin 170 



been substituted for tillage in order to maintain production under 

 the conditions of lessened cultivation. 



Many general observations lead one to believe that the present 

 method of using commercial fertilizers in the production of hay 

 is often unprofitable. There seems to be very little doubt that, 

 in the common use of fertilizers, a very large proportion of the 

 plant food added is never converted into profitable plant 

 products. It is doubtful if the use of commercial fertilizers 

 can long be substituted for tillage and other important soil factors 

 which enter into profitable plant production. 



The soils of New Hampshire are extremely varied in character 

 and are, for the most part, of granitic origin. Almost any type 

 may be found between the limits of sand and pure boulder clay. 

 The sands in many instances are rich in feldspathic and other 

 minerals. Many of the types have been considerably washed 

 while others seem to have been formed in place. Areas of lime- 

 stone soil are very limited and are found in only a few sections. 



In connection with the use of commercial fertilizers in the 

 production of grass, some very interesting facts have been found. 

 Many of the grass fertilizers carry a large amount of potassium. 

 Also the tillable soils are on the average very rich in potassium. 

 Those soils which are relatively poor in potassium contain large 

 amounts in the aggregate. Some of the boulder clay soils con- 

 tain as high as 3% potassium oxide. Assuming that an acre foot 

 of soil weighs three million pounds, such a soil would contain 

 forty-five tons potassium oxide per acre. Some of the medium 

 clay soils carry about 2% potassium oxide while the light soils 

 carry still less. Some very sandj'' soils have been found which 

 contain as much as 1% potassium oxide. Such soils carry a con- 

 siderable amount of mineral in connection with the sand. 



With these large quantities of potassium oxide present in the 

 soil, there came the question of the use of potassium in commer- 

 cial fertilizers. Could not the soil, under proper tillage condi- 

 tions, supply enough potassium for the needs of the crop without 

 the addition of potassium from artificial sources? It is a fact that 

 where potassium is added in comparatively large quantities as a 

 fertilizer constituent, that this amount is very insignificant when 

 compared with the amount of potassium present in the soil under 

 natural conditions. To illustrate: sixty pounds of potassium 



