1856.] invohedin Agricultural Experiments. 291 



sions, a series of trials on a scale rather befitting a public body 

 than a private individual. As a general result of these it was found 

 that mineral manures alone did not suffice for full crops of cereals, 

 but that ammonia was required to be added to them for proper 

 success. The air then did not supply enough of the latter substance. 

 As regards root crops, such as turnips, the result was different, 

 mineral bodies, especially phosphates and sulphates, being found to 

 be highly beneficial, while ammonia did not appear to be required 

 as an addition ^to the manure. Alkalies were found favourable to 

 the leguminous crops. When the different habits of the plants are 

 considered, the results appear to be more comprehensible. Cereals 

 have a small expanse of leaf, and a short period of life. In the 

 17 weeks of their growth at Rothamstead, they receive 800 or 900 

 tons of water as rain, of which about 500 tons are evaporated by 

 passing through the crop. But in reality they make half their dry 

 substance in four or five weeks, pjven admitting that they re- 

 ceived all the ammonia of the rain, only about 12 lbs. of nitrogen 

 would be thus received by the crops, instead of the 50 lbs. which 

 they require. In the case of the short-lived cereals, to which a 

 gain of time is everything, it would be natural to expect that an 

 augmentation of ammonia would be favourable to their growth. 



The turnip, on the other hand, grows steadily over 21 weeks, 

 making dry substance all the time, and with its broad leaves can 

 take in more air food. Then, as regards earth food. The wheat 

 has long greedy roots, which it throws out in all directions in search 

 of food ; the turnip, with its small delicate fibres, is dependant on 

 the food in its immediate vicinity. The wheat is an accomplished 

 forager, like the light Zouave, and if food be in the soil it will pro- 

 cure it. The turnip is like the bulky English soldier who, unless 

 food is brought up to his tent door, is likely to fare badly. These 

 habits of the plants determine why an artificial supply of an ingre- 

 dient of air food is more necessary to one, and of earth food to the 

 other ; but this result, though a valuable accession to our know- 

 ledge, in no way shakes the original laws of nutrition. 



It is not, however, quite clear that even cereals with high cul- 

 tivation may not get ammonia enough for themselves out of the 

 air, without an artificial supply being given. At Lois Weedon, a 

 soil frequently stirred and well worked has, without any manure, 

 grown for ten years full crops of wheat of 34 bushels, on half an 

 acre placed under growth, the other half being kept under fallow. 

 In this instance, the absorption and radiating power of the soil 

 being much increased by the frequent stirring, more anmionia is 

 absorbed, and more dew containing ammonia is deposited, while 

 the weathering of the soil has hitherto liberated sufficient mineral 

 ingredients for full crops. 



If no other conclusion had been drawn by farmers from the 

 Rothamstead experiments than that, in soils of an ordinary condition, 

 an artificial supply of ammonia must be furnished to cereals, a 



