58 



influence on the yield. In opposition to this, Hellriegel* 

 found sulphate of ammonia more effective on the leguminous 

 crops generally than nitrate of soda. 



On the whole, however, the conclusion cannot be avoided 

 that no nitrogenous manure will prove economical for 

 application to beans; and the subject need not be further 

 discussed. 



CLOVER. 



With this leguminous plant, as with beans, nitrogenous 

 manures are often of little use ; but the evidence afforded 

 by experiment is not quite so consistent as in the case of 

 beans. 



In an early experiment at Rothamsted, the average pro- 

 duce of red clover hay per acre, from six plots, manured in 

 various ways, or left unmanured, was 4 tons 7 cwt. 76 Ibs.; 

 while six similar plots, receiving exactly the same manures, 

 but with the addition of ammonia salts to each, only 

 averaged 4 tons 4 cwt. 3 Ibs. a falling off of about 3! cwt. 

 On the other hand, in the attempted continuous growth 

 of clover at Rothamsted, the produce of hay per acre on 

 the average of the seven crops grown in 29 years was, with 

 mineral manures only, 4171 Ibs. per acre, and with mineral 

 manures and nitrogenous manures in addition, 4555 Ibs. 

 per acre a gain of about 3^ cwt. from the use of the nitro- 

 genous manures. 



Somewhat more favourable results have sometimes been 

 obtained. For instance, Von Knieriemf found, on the 

 average of two seasons, an increase in the clover crop of 

 52 per cent, by the use of sulphate of ammonia and super- 

 phosphate, against 30 per cent, increase with super- 

 phosphate only. In the former case, the benefit of the 

 manuring extended into the second year ; but with super- 

 phosphate only, no effect was perceptible after the year of 

 application. 



The general conclusion arrived at as the result of ex- 

 periment is that, though nitrogenous manures often give 

 an appreciable increase when applied to the clover crop, 

 yet they are very uncertain in their action, sometimes 

 actually diminishing the crop. In any case, they rarely 

 prove economical ; the cost of the manure usually exceed- 

 ing the value of the extra produce. 



GRASS LAND. 



The effect of any manuring on grass land is particularly 

 difficult to estimate, for mere bulk of produce is only one 

 of several factors such as the botanical composition, the 

 feeding value, and the readiness with which stock eat the 

 grass. We will first consider the effect of sulphate of 

 ammonia on the weight of the crop only. 



* "Ann. der Landw.," VII. and VIII. f "Bied. Centr.," 19. 



