2 9 



manure produced a small crop (which would, of course, 

 leave comparatively little organic matter in the soil), the 

 residue would also produce little effect. But the exact 

 opposite of this occurred in the above experiment. A dry 

 season on the light soil at Woburn may interfere with 

 nitrification during the hottest part of the year, when 

 normally it takes place most rapidly. If this happens, the 

 washing away of nitrogen in the form of nitrate during the 

 autumn will be comparatively small. 



The comparison given in Table XIII. between ammonia 

 salts and nitrate of soda is important, because it illustrates 

 one marked difference in the action of these two principal 

 nitrogenous manures. The figures relating to nitrate of 

 soda show clearly that if this manure is not used by the 

 crop to which it is applied, it will be practically lost ; for 

 on plot 9A, though in the dry year of 1895 ^ e cr P was 

 a good deal under the average obtained by the direct 

 application of nitrate, in 1896 the residue gave a crop 

 below the average of those obtained from such residues. 

 (See Table XII.) On the other hand, the residue of the 

 ammonia salts, under the same conditions, produced a crop 



3*8 bushels above the average. 







EFFECT OF APPLYING TOO MUCH SULPHATE. 



Passing on from this question, a word must be said with 

 regard to the effect of different quantities of sulphate of am- 

 monia on crops. All the injurious effects arising from the 

 use of nitrogenous manures too late in the season such as 

 the late ripening of the crop, the over-production of leaf and 

 poor yield of grain, &c. may also be produced by their 

 application in too large quantity. In both cases, it must 

 be observed, the injury is done, not by any unsuitability 

 of the manures for use on the farm (a conclusion too often 

 arrived at from very insufficient evidence), but by their use 

 in an injudicious manner. 



The quantities of sulphate of ammonia usually suitable 

 for the chief farm crops will be mentioned later, when the 

 crops are considered in detail. For the present, however, 

 it must be noticed that no absolute rule can be laid down 

 as to the quantity of any manure that will give the best 

 results. Soils and seasons differ enormously ; and the 

 effect of manures varies in proportion. Even in the case 

 of similar soils and seasons, differences in condition of the 

 former may cause different results from any dressing of 

 manure. The benefit arising from the use of nitrogenous 

 manures on barley after wheat, and the injury they do to 

 barley after roots fed off by sheep, is a good example of 

 this. 



The effect of the application of a given quantity of sul- 

 phate of ammonia or other nitrogenous manure, depends 

 also on whether the crop has a plentiful supply of the 



