106 MAINE AGRICULTURAL EXPERIMENT STATION. 1908. 



All of these fertilizers carry less nitrogen than a large crop 

 would remove, but in practice one should depend somewhat upon 

 the nitrogen of the soil and particularly that of the roots and 

 stubble which are plowed under. The phosphoric acid and 

 potash being in marked excess, the question naturally arises in 

 case of failure could it have been due to the lack of nitrogen. 

 While the Prentiss Fertilizer did not carry nitrate nitrogen, it 

 had about a third of its nitrogen in the water soluble form. 

 Applied on wet land in such a season as 1907, it is possible that 

 some of this may have leached out and there would have been a 

 deficiency for this reason. The same loss from leaching, if it 

 occurred, would have taken place had nitrate of soda been used. 



While nitrogen in any available form can be used by plants, 

 it is generally agreed by plant physiologists that plants only take 

 it up after the nitrogen has been changed into nitrate nitrogen. 

 In the case of ammonia salts and organic nitrogen, the change 

 to nitrate nitrogen goes on in the soil due to the action of 

 bacteria. This change takes place only slowly in cold and wet 

 soil and does not proceed at all rapidly until the soil becomes 

 warm. Hence in the first early days of spring, organic nitrogen 

 applied in a fertilizer may be practically unavailable to a plant. 

 For this reason the Station has always recommended that a 

 potato fertilizer carry about a third of its nitrogen in the form 

 of nitrate nitrogen. The potato seems to demand nitrogen in 

 the early part of its growth and while organic nitrogen becomes 

 available later, it might happen that in the early part of the sea- 

 son, a crop manured with only organic nitrogen or nitrogen in 

 the form of ammonia salts, would make a poor growth during 

 the first weeks. It is, of course, possible that loss, so far as the 

 loss can be attributed directly to the fertilizer, was due to the 

 lack of nitrate nitrogen in the fertilizer. There was apparently 

 no fraud, or attempt at fraud, on the part of the manufacturers 

 in omitting nitrate nitrogen because the nitrogen which they fur- 

 nished in the form of ammonium sulphate was according to 

 market prices in 1907 but little cheaper than the nitrogen in the 

 form of nitrate and equally permissable under the State law. 



One of the Station chemists spent a week beginning November 

 11, visiting farmers in the vicinity of Easton and Presque Isle 

 and talked with them regarding the potato crop, particularly in 

 connection with the R. T. Prentiss Company's fertilizer. Some 



