Potato Culture. 157 



Phosphoric acid, 4.219 lbs. 



Nitrogen, 3,053 " 



Potash, 16,317 " 



An analysis of the soil from the plats on which the potatoes 

 were grown shows the following amounts of potential plant-food 

 per acre to the depth of one foot : 



Phosphoric acid 3>784 lbs. 



Nitrogen, 3.074 " 



Potash, 1^,063 " 



This computed to a depth of eight inches, for comparison with 

 the previous analysis given, shows the following amounts: 



Phosphoric acid, ....'.. 2,523 lbs. 



Nitrogen, 2,049 " 



Potash, 8,042 " 



It will thus be seen that with a soil containing little more than 

 half the amount of potential plant-food ordinarily contained in 

 soils, a yield was secured from three to four times the average 

 yield of the state. 



The fact has been mentioned that this soil was gravelly. In 

 securing a sample for analysis we found in the surface foot 56.79 

 per cent of material fine enough to pass through a sieve of 18 

 meshes to the inch, and 41.85 per cent of gravel which would 

 not pass through the sieve. The loss due to drying and waste 

 was 1.36 per cent. 



In the ordinary analysis of soils the gravel is not taken into 

 consideration and only that part is now analyzed which passes 

 through a sieve of 50 meshes to the inch. To determine more 

 fully what potential plant-food was in the land, it was decided to 

 analyze the gravel, or that portion which failed to pass through a 

 sieve of 18 meshes to the inch. The result of the analysis showed 

 the following amounts of potential plant-food locked up in the 

 gravel of a surface foot of one acre of the land : 



Phosphoric acid 4,008.8 lbs. 



Potash, 11,329.8 " 



The manipulation that was necessary to cause the soil to pass 

 through the sieve also broke down some of the gravel. It was 

 found after sifting all the soil out that by working the remain- 

 ing gravel with the hand a portion of it was so rotten that it 



