On the Groioth of Barley hy different Manures, S^c. 493 



That exclusively mineral manures, and especially those con- 

 taining phosphoric acid, annually increased the produce of barley ; 

 even doing so in the first year of their application on land in the 

 condition described. 



That with barley grown continuously on the same land (as was 

 the case with wheat), nitrogenous manures had a much more 

 striking- effect than mineral manures. 



Tliat by the annual supply of nitrogenous manures alone (nitrate 

 of soda or ammoniacal salts), larger successive crops both of corn 

 and straw were obtained, than by the annual use of 14 tons of 

 farmyard manure — with all its minerals, and certainly more nitro- 

 gen than either the nitrate or ammoniacal salts employed by its 

 side. 



That within certain limits, even on this comparatively exhausted 

 soil (and it would probably be more neaily so on soils in ordinarv 

 condition for the crop), nitrate of soda, ammoniacal salts, and 

 rape-cake, all increase the produce of barley, approximately in 

 proportion to the amounts of nitrogen they respectively supplied. 

 Their comparative effects will, however, vary somewhat according 

 to season, the nitrate being generally more rapid in its action. 



That to obtain a maximum amount of increase in proportion 

 to the nitrogen given in manure, the bailey-crop will, on the 

 average of seasons, bear a considerably less acreage amount of it 

 than is required by the wheat crop under similar circumstances. 



That the effect of a given amount of nitrogen, if not excessive, 

 will be considerably increased by the addition of certain mineral 

 manures, especially those containing phosphates. The action of 

 the mineral manures is very much increased under such circum- 

 stances ; that is, their application gives very much more increase, 

 when there is present a liberal supply of available nitrogen loitldn 

 the soil, than when there is not. 



In other words, a soil brought by previous cropping into a 

 condition to require manure of some kind before it will grow a 

 full crop of corn, when afterwards cropped year after year with 

 barley, only yields full crops when a liberal amount of nitrogen 

 is supplied to the soil. Mineral manures, especially phosphates, 

 considerably increase the action of the nitrogen so supplied ; but 

 the effect of such mineral manures on the increase of crop, will be 

 extremely limited, without there be a liberal amount of available 

 nitrogen within the soil itself. 



The conclusions enumerated above have been arrived at by the 

 consideration of experiments on the growth of barley by various 

 constituents of manure, applied year after year on the same land. 

 It will be interesting, with the information thus gained, to inquire 



