48 RESULTS OF EXPERIMENTS AT ROTHAMSTED, 



Dr. B. E. Dietzell made vegetation experiments, in which plants 

 were watered with distilled water, the drainage was returned to the 

 soils, and the pots and their contents were exposed to free air, but 

 protected by a linen roof. A rich garden soil, containing 0-415 per cent. 

 of nitrogen, was used, several different conditions as to manuring were 

 adopted, and Peas and Clover were the subjects of experiment. Thus, 

 the plants were of the Leguminous family ; but notwithstanding this, 

 there was, in no case, a gain of nitrogen. In one there was neither 

 gain nor loss, and in all the others there was a loss, in some cases 

 amounting to 15 per cent, of the total nitrogen involved. 



That there should be loss with a soil containing 0-415 per cent, of 

 nitrogen, that is about three times as much as most ordinary arable 

 soils, is not at all surprising; and it is seen that, neither from the 

 combined nitrogen of the atmosphere, or that due to other accidental 

 sources, nor from free nitrogen, either directly or indirectly,, did these 

 reputed " nitrogen collectors " gain nitrogen to compensate the losses 

 from the rich soil. 



Professor Frank also made vegetation experiments in free air. His 

 soil was a humus-sand, containing only 0-0957 per cent, of nitrogen ; 

 distilled water was used for watering, and the vessels were deep and 

 narrow cylinders, without any arrangement at the bottom for drainage, 

 or for aeration. In three experiments without a plant, in one with 

 two Lupins, and in one with one Lupin and Incarnate Clover 

 together, there was a loss of nitrogen ; whilst in one with three Lupins, 

 and in one with one Lupin, there was a gain. Frank considered it 

 probable that where a loss was indicated with vegetation, there had 

 nevertheless been a gain, but not enough to compensate the loss. 



In another experiment, with a soil about 12 times as rich in 

 nitrogen, and many times richer than ordinary arable soils, he found a 

 loss, due mainly to evolution of free nitrogen ; and, referring to this 

 result, he says that, if such losses take place in ordinary agriculture, 

 there must be natural compensation. 



In the experiments in the deep and narrow vessels, without 

 drainage, and without plants to cause evaporation, movement, and 

 aeration, loss by evolution of free nitrogen is only what would be 

 expected. Such loss would also be expected in the two cases of loss 

 with growth, in both of which there was admittedly decomposing 

 organic matter. It was also to be expected in the very rich soil. But 

 it is doubtful whether, in the two cases of gain with growth, and 

 therefore movement within the soil, and aeration of it, there would be 

 any loss. In none of the experiments with loss, however, were the 

 conditions comparable with those of ordinary soils, under ordinary 

 treatment ; and the losses found cannot be taken as any indication of 

 what takes place in ordinary practice. It is probable that, in such 

 practice, the loss by evolution of free nitrogen is much less than is 

 generally assumed in discussions of this subject. Doubtless there is, 

 however, frequently considerable loss by the drainage of nitrates. 



Frank considers that, independently of direct evidence against the 



