EFFECT OF COMMON SALT. 339 



of the barley plants as mueh or even more food tlian was 

 the case with the plot manured witli guano, on whicli the 

 sum of the nutritive substances was greater. 



In estimating the results of these experiments we must 

 take into account the fact established by Dr. Zoeller, that 

 soda seems to take a definite part in the production of 

 barley seed. It is clear that the nitrates used did not 

 simply act as agents in distributing other nutritive sub- 

 stances, but the soda as well as the nitric acid had their 

 own share in the production of the crop. In the fourth 

 experiment the field received as much nitric acid as in the 

 second, but the base combined with the acid was potasli 

 and not soda ; and in the fifth experiment tlie addition of 

 common salt produced a remarkable increase in the corn 

 crop. However, in the third and fifth experiments tlie 

 quantity of salt apphed was evidently too high, and the 

 excess brought down the crop below that obtained with 

 nitrate of soda alone. 



Upon the more exhausted field in 1858 the crop 

 obtained by guano in corn and especially in straw ex- 

 ceeded all the rest. In the arable soil of this field the 

 amount of nutritive substances was on the whole smaller, 

 and the addition of fresh elements of food made itself felt 

 in a much higher degree than the distribution or dissemi- 

 nation of the substances already present in the soil. Still 

 by the addition of common salt the crop of wheat was 

 also increased. 



The effect of potash upon wheat is as striking as that of 

 soda upon barley. 



As reo:ards the effect of common salt and salts of soda 

 generally, the analysis of the ash of turnips and potatoes, 

 kitchen-garden and meadow plants, shows that, as a rule, 

 the ashes of the former contain a considerable quantity of 

 soda, and the ashes of the latter are proportionately rich 



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