OFFICIAL INSPECTIONS 74. 281 



siderable value in releasing potash for certain crops. There was 

 very little gained from the use of common salt with the potato 

 crop. This experiment indicated during its whole course that 

 the application of soda to the granitic soils helped to insure the 

 production of normal crops, even without the addition of pot- 

 ash. At the Experiment Station at Rothamsted, England, 

 nitrate of soda has been found to be of marked value in the 

 growing of crops, irrespective of the nitrogen which it carries. 

 Dr. Hall concludes from these experiments that "in practice the 

 dressing of nitrate of soda on any but the lightest soil will dis- 

 pense with the necessity of a specific potash manuring even for 

 potash loving crops." 



Lime (calcium oxide), hydrated lime (calcium hydrate) air- 

 slaked lime (calcium carbonate), or ground limestone (calcium 

 carbonate), is helpful in liberating potash from the organic 

 matter of the soil. The effect of lime upon the mineral potash 

 of a soil is not so well determined, and there is a difference of 

 opinion. The best New England authorities think that it has 

 little or no effect in freeing mineral potash. 



Gypsum (calcium sulphate) has been found to have some 

 eff'ect in replacing potash in the soil. Its price, however, is 

 probably too high for general application the present year. 

 Acid phosphate, however, of necessity, always carries gypsum. 

 Hence all mixed fertilizers containing available phosphoric acid 

 also carry gypsum. In general multiplying the available phos- 

 phoric acid in a fertilizer by two and a half will give the ap- 

 proximate pounds of gypsum in fertilizers. That is, an acid 

 phosphate carrying i6 per cent of available phosphoric acid 

 will carry about 40 per cent of gypsum. A ton of fertilizer 

 with ten per cent available phosphoric acid would carry about 

 500 pounds of gypsum. 



Growing Potatoes Without Potash. 

 Potatoes are the chief cash crop grown in Maine. It is of 

 first importance for the grower to have what facts are available 

 relative to the likelihood of obtaining a crop in 19 16 without 

 the application of potash. Foreseeing the possibility that the 

 fertilizers in 1916 would contain very little, if any, potash, the 

 Maine Agricultural Experiment Station began in 191 5 at Aroos- 

 took Farm, a series of experiments to determine the effect o£ 



