102 The Rothamsted Barley Experiments. 



4*75 per cent, of nitrogen. It also contains a large amount 

 of carbonaceous organic matter, and about 8 per cent, of 

 mineral matter. By the annual application of rape-cake, 

 whether without or with the addition of mineral manures, 

 more barley than the average crop of the country has been 

 obtained ; but, in proportion to the nitrogen it contained, less 

 than by ammonia-salts or nitrate of soda. The nitrogen of 

 the nitrogenous organic matter of rape-cake is much less 

 rapidly available than that of ammonia-salts or nitrates ; 

 indeed, analysis of the soil has shown that the rape-cake has 

 left a considerable residue of nitrogen near the surface. 



Since, for twenty or more years in succession, ammonia- 

 salts, or nitrate of soda, with mineral manure (without 

 silica), have yielded considerably more of both wheat and 

 barley than the average crops of the country, and more also 

 than either farmyard manure or rape-cake, it follows that the 

 return to the soil of carbonaceous organic matter as manure 

 is unessential, so far as the successful growth of either of 

 these crops is concerned. 



Thus, from a comparison of the produce obtained by the 

 different manures, it has been shown that carbonaceous 

 organic matter, supplied so largely in farmyard manure and 

 rape-cake, is, at any rate, not essential as manure for either 

 wheat or barley ; that mineral manures alone will not yield 

 fair crops of either; that nitrogenous manures give much 

 more produce than mineral manures alone ; and that the 

 mixture of nitrogenous and mineral manures will give full 

 crops for many years in succession. In other words, the 

 supply by manure of matter yielding, by decomposition, 

 carbonic acid and other carbon compounds within the soil 

 has little or no effect ; mineral manures alone will not enable 

 the growing plant to obtain sufficient nitrogen from the soil 

 or the atmosphere. When nitrogen in an available form was 

 liberally provided, the mineral constituents of the soil were 

 insufficient for its full effect ; but when so supplied, the 

 mineral manures, which alone had little effect, greatly 



