302 AGRICULTURE OF MAINE. 



but as containing a certain proportion of zeolitic bodies imme- 

 diately between feldspar and kaolinite. Any soluble salt, and 

 particularly a soluble soda salt, will react with these zeolites and 

 exchange bases to an extent depending on the relative masses 

 of the two bodies, hence nitrate of soda acts on the clay of the 

 soil and brings some potash into solution. To a certain extent 

 this action takes place and in practice the dressing of nitrate of 

 soda, on any but the lightest soil, will dispense with the neces- 

 sity of a specific potash manuring, even for potash loving 

 crops." 



No experiments in New England have been made along this 

 line with the exception of a limited amount at the Amherst, 

 Massachusetts, Experiment Station. The soil there is a silt, 

 and not granitic in its origin. Director Brooks did not find 

 any specific (benefit from the application of nitrate of soda to 

 that soil as a liberator of potash. 



Lime (calcium oxide), 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 <letermined, 

 and there is a difference of opinion. The 'best New England 

 authorities think that it has little or no effect in freeing min- 

 eral potash. 



Gypsum (calcium sulphate) has been found to have some 

 eft'ect in replacing potash in the soil. Its price, hoavever, is 

 proba/bly too high for general application the present year. 

 Acid phosphate, however, of necessity always carries g}'psum. 

 Hence all mixed fertilizers containing availasble phosphoric 

 acid also carry gypsum,. I'n general, multiplying the available 

 phosphoric acid in a fertilizer by two and a half will give the 

 approximate pounds of gypsum in fertilizers. That is, an aicid 

 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. 



Mixed Commercial Fertilizers in 191 6. 



The present year fertilizers may be had ranging from one to 

 six per cent of ammonia, from eight to ten per cent of available 



