161 



l)oth barley ami wheat were foniul to be iiuicli more suseeptible to this trouble 

 than oats. 



In the Woburn experiments sodium nitrate produces no such unfavorable 

 effect as that foIlowin>: the use of aninionium salts. In these experiments, 

 however, a mixture of the sulphates of i)otassium. so<1ium. and magnesium 

 with superpliosi)hate has apparently produced no injurious results as yet upon 

 the barley crop, the effect of this dressing corresponding to that obsened upon 

 the cereal crops on plat 8 in our tests. When to this dressing, however, am- 

 monia salts are added, the yield is reduced to a point below that of the unfer- 

 tilized land unless lime is added, but with lime the mixed minerals and anunonia 

 salts produce a larger yield than the same mixed minerals with an equivalent 

 quantity of nitrogen carried in sodium nitrate. 



i;)octor Voelcker has studi<'d. by jiot tests, the effect of those fertilizing sub- 

 stances upon the ]ihysical condition of the soil, and finds: 



"(1) That there is a great difference in the mechanical condition of the soil 

 produced by the different ai)i)licati<)ns, in regard to the caking of the surface 

 and the rapidity with which water passes through it. Thus distilled water 

 (say rain water) goes through most slowly, the moistui"e being mostly retained; 

 nitrate of soda fonns a hard crust on the surface, thereby often retaining the 

 water on the surface: with sulphate and nnnMate of ammonia a crust is also 

 formed, but the drying of the soil causes large fissures to appear, and through 

 these the litpiid flows away more (piickly than in the other cases. 



"(-I Variable amounts of organic matter are removed, the distilled water 

 removing comparatively little, while ammonia salts give deeply colored solu- 

 tions when the drainage first runs. 



"(3) As regards removal of lime, it has been ascertained that the order in 

 which this, as well as magnesia, is washed out is: (n) (the least) water. (&) 

 nitrate of soda, (c) sulphate of anunonia. and ((/) (the most) nuiriate of am- 

 monia. The rate of removal of lime is about twice as rapid with nuiriate of 

 ammonia as with nitrate of soda. The results with iwtash. ])hosphoric acid, etc., 

 are being worked out. 



"(41 It has been noticed that the rate of removal of lime varies greatly 

 with the season of the year, being most active in the spring and summer (the 

 time of most active nitrification ) and almost ceasing toward the winter, but 

 commencing again the following spring." « 



He has also attacked the (luestion as to the nature of the acidity of this 

 soil, first by thoroughly washing the soil, and, second, Ity drying it on a stone 

 floor for several months. Both methods resulted in the removal of the acid 

 character, and, further, the acidity of the liquor from the washed soil disap- 

 peared after exposure for a time to the air. Discussing these results Doctor 

 Voelcker says : 



" At first sight one would be disposed to think that the acidity might arise 

 from sulphuric acid or hydrochloric acid consequent on the continued use of 

 sulphate and muriate of ammonia on a soil poorly supplied with lime. But 

 this has been shown not to be so, for the washings of the soil * * * are 

 not acid with either of these two acids ; however, the fact that the acidity 

 passes off equally on the exposure of the soil to the atmosphere and on expos- 

 ure of the soluble liquid poured oft' when the soil is washed shows that it can 

 not be due to mineral acids, but is more probably the result of a feebly soluble 

 organic acid or acid salt." & 



Doctor Voelcker has carried this inquiry further by grow-ing plants in soil 

 from this plat (1) after it had been exposed to the air as above mentioned, (2) 

 after thoroughly washing it, (3) in soil taken from the headland of the field 

 and treated with liquid used in washing the acid soil, (4) in a check pot of 

 the untreated soil from the acid plat, and (5) in another to which calcium chlo- 

 rid had been added. The results were that neither wheat nor barley would grow 

 on the untreated soil nor on that treated with calcium chlorid. but both grew 

 well on the washed and exposed soils, and also on the soil treated with the 

 water used in washing. From these results Doctor Voelcker draws the follow- 

 ing conclusions, stating, however, that they are only preliminary and require 

 much further investigation before they can be definitely formulated : 



"(1) That the acidity of the soil, brought about by the continual use of am- 

 monia salts, or else the condition of soil consequent on its formation, is the 

 cause of the failure of the land to produce barley and wheat. 



"Jour. Roy. Agr. Soc. England, 64 (1903), p. 357. 

 b Ibid., p. 358. 



2133(>— No. 164—06 M 11 



