62 RESULTS WITH BARLEY 



of our discussion, instead of the average of the whole twenty 

 years. 



Return per unit of Ammonia. On plot 5 the return per 

 cwt. of sulphate of ammonia of 10-5 bushels of barley is very 

 nearly the same as the return obtained on the corresponding 

 plot 4A, in the Rothamsted experiments. The Woburn return 

 is thus not considerably above that obtained at Rothamsted, 

 as it was in the case of the wheat experiments, but nearly 

 equal to it. The causes of the better return from ammonia 

 salts at Rothamsted in the case of barley have been already 

 noticed. 



The double dressing of ammonia salts on plot 8 gives appa- 

 rently a much less profitable return than the smaller dressing on 

 plot 5 ; if, however, we take into account the effect of the residue 

 of the ammonia salts applied on plot 8, the return from the am- 

 monia is greatly improved. Plot 8 in the barley experiments at 

 Woburn was divided after the first six years, and the ammonia 

 salts were subsequently applied alternately to the two halves, 

 as in the wheat experiments already described. We have thus 

 each year a means of estimating the effect of the residue of the 

 manure applied in the preceding season. If we add the increase 

 of crop produced by the residues of manure on plot 8 to the 

 crop credited to this plot in Table XV., we have an average 

 produce of 56*5 bushels of barley in the sixteen years, and a 

 return of 9-2 bushels for each cwt. of sulphate of ammonia 

 employed. It by no means follows, however, that if the larger 

 dressing of ammonia salts, plus the residue of the preceding 

 dressing, had been every year available on the same plot, that 

 an equally good return would have been obtained ; the crop 

 would probably under these circumstances have gone down, 

 and an inferior return would have been obtained. 



Influence of Ash Constituents. On the Woburn soil 

 the application of superphosphate and alkalies is apparently 

 much less necessary than at Rothamsted. At Rothamsted the 

 addition of superphosphate and alkalies to 200 Ibs. of ammonia 

 salts increased the crop by an average of 13-7 bushels during 

 the first twenty years. At Woburn the same quantities of 

 superphosphate and alkalies only produce an average increase 



