28o MAINE AGRICULTUR-\L EXPERIMENT STATION. I915. 



meeting recently to discuss this subject and arrive at definite 

 recommendations for the crops for 1916. Based upon this dis- 

 cussion and the conclusions there reached, supplemented by a 

 few special studies made by this Station, chiefly at its Aroostook 

 Farm, the writer prepared an address for the ]\Iaine Seed 

 Improvement Association.* The following is taken from th.it 

 address : • • 



POTASH. 



Feldspar carries considerable potash, but experiments have 

 not shown it to be of any direct value as applied to land. 

 There are patented processes for extracting potash from feld- 

 spar which would doubtless come into practice were it not for 

 the fact that as soon as the war is over potash will probably go 

 back to its normal price. While it is hoped that supplies of 

 potash may be found that will make this country independent 

 of foreign sources, not enough will be produced before planting 

 time to at all relieve the present shortage. 



Outside of a limited amount of ashes, available potash is 

 practically unobtainable for most crops. Commercial fertilizers 

 for 19 1 6 will, for the most part, be made to carry no potash or 

 at the most only one per cent. This one per cent will add five 

 dollars to the cost of fertilizer per ton. 



POTASH LIBERATORS. 



There are no such things as potash substitutes in agriculture, 

 but some materials, such as the sodium and calcium salts, 

 will under certain conditions more or less replace the potash in 

 the soil and render it available for the growing of plants. 



Among the soda salts are nitrate of soda, soda ash and 

 common salt. Gypsum (calcium sulphate) is the most impor- 

 tant calcium salt. x\lkaline sources of lime and soda such as 

 calcium carbonate and lime and of soda ash, do not seem to be 

 so effective in releasing the potash of soils as are the chlorides 

 and nitrates. 



Field experiments conducted for 20 years at the Rhode 

 Island Experiment Station seem to indicate that soda has con- 



*This is printed in pamphlet form under the title of "Growing Crops 

 Without Potash in 1916," and can be had on application to the Station. 



