30O AGRICULTURE OF MAINE. 



valuable source of nitrogen. Dried starfish carry about five 

 per cent of nitrogen, two per cent of lime, but practically no 

 potash or phosphoric acid. 



PHOSPHORIC ACID. 



Bone and the mineral phosphates which are found from fos- 

 sil bones are the sources of commercial phosphoric acid. The 

 finely ground mineral phosphates, called floats, may have some 

 place in our agriculture with the advance in price of acid phos- 

 phate. These have been largely recommended for use in the 

 A'liddle West. It is to be remembered that the value of their 

 crops per acre is only about a third of that of the average crop 

 in New England. The more available acid phosphates, even 

 at a higher price, have proven to be economical for New Eng- 

 land conditions. In no case would the speaker advise the use 

 of floats for direct application to the land for most crops, as 

 they are slow in action. In Ohio they have been found to be a 

 valuable addition to farm manure. 



Basic slag is a good alkaline source of phosphoric acid, but 

 its price is prabalbly too high to be considered in 1916. 



Both bone and bone tankage are much more available than 

 floats. Of somewhat slow action they are valuable in making 

 up a part of the phosphoric acid in mixed goods, whether these 

 be home or factory mixed. 



Acid phosphate is still the best source of phosphoric acid for 

 Maine farms. The price this year is, however, high. Quickly 

 available phosphoric acid has a tendency to hasten the develop- 

 ment of the root system of plants, and for this reason it is par- 

 ticularly valuable for crops that need to make an early growth. 

 Starting the plants early in this way gives them a longer season 

 and makes it more possible for them to utilize plant food in 

 the soil than would otherwise be the case. 



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 feldspar 

 which would doubtless come into practice were it not for the 

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

 t)ack to its normal price. 



