May, m±) 



435 



Scientific Agriculture, 



stant, and are known as equivalent 

 quantities. As these quantities are dif- 

 ferent in the case of each element, it 

 follows that, when one of them is sub- 

 stituted by another, in a salt, there 

 must be a change from the absolute 

 weight of the old compound to that of 

 the new. 



Plants, again, all contain organic acids, 

 which vary in nature in the different 

 kinds. These are necessary, in order 

 that the life-processes of the plant shall 

 continue. They usually exist combined 

 with one or more of the bases, acts as 

 a stimulus to the formation of the 

 organic acids, and this matter receives 

 support from the observation of de 

 Saussure, to the effect that the bases 

 are found in greatest quantity in those 

 parts ot the plant nearest to the re- 

 gions in which assimilation is taking 

 place ; thus the leaves contain propor- 

 tionately more ash than the branches, 

 and the latter more ash than the trunk. 



Liebig stated further that it is not 

 likely that a plant, under normal con- 

 ditions, produces a much greater quan- 

 tity of any given acid than it requires 

 for the existence ; it is also to be ex- 

 pected that the amount of alkaline base 

 in a plant will always remain the 

 same, no matter in what kind of soil 

 it is growing. It was explained by Liebig 

 that any deficiency in regard to one 

 base would be supplied by the substi- 

 tution of an equivalent amount of 

 another base. Ic results from this cir- 

 cumstance that, as the weights of the 

 base vary, the absolute weight of the 

 ash must differ according to the kind 

 of substitution in the compounds which 

 it contains. Another conclusion reached 

 by Liebig, which is pertinent to the 

 matter under discussion, was that, even 

 where plants have been grown in soils 

 containing very different proportions 

 of lime magnesia and potash, the equi- 

 valent amount of these bases, expressed 

 in terms of oxygen, is the same, within 

 reasonable limits, for similar quantities 

 of wood and of the ash. 



The results of the work Liebig and 

 Others were expressed more clearly by 



Champion and Pellet, and their state 

 ments virtually corresponded with what 

 has just been put forward. In regard to 

 the interchange-ability of the bases, the 

 author of the paper mentioned at the 

 head of this article agrees that this 

 exists, but draws attention to the pre- 

 sence of limits to the extent to which 

 any one base may be excluded by the 

 substitution of one or more that are 

 different. When this critical point is 

 passed, the plant ceases to develop 

 favourably ; this fact is supported by 

 the work and opinion of Loew in Japan, 

 Bernardini, and May at Washington. 

 Claassen has also reached the same con- 

 clusion, as the result of investigations 

 with sugar beets, and Pellet has shown 

 that the heart rot of the beet is most 

 prevalent in soils possessing an undue 

 proportion of potash and a deficiency of 

 magnesia. Further Marchal, of Gem- 

 bloux, has proved that the formation of 

 nodules on the roots of leguminous 

 plants receives interference from an 

 excess of potash in the soil, and that the 

 development of the plants themselves is 

 adversely affected ; so that the ultimate 

 effects are lessened yields, with the 

 minimum fixation of atmospheric nitro- 

 gen. Lastly, other investigators nave 

 made the observation, in the case of 

 certain plants, that an excess of potash 

 produces decay ; and that if some of the 

 potash is replaced by other bases, as for 

 example magnesia, the plants can be 

 made to revive and resume normal 

 growth. 



Sufficient has been said to indicate 

 that much harm is likely to arise through 

 the absorption of an undue proportion 

 of potash by plants. The condition may 

 bring about large changes in the nature 

 of the crops; and it certainly causes a 

 diminution in the power of plants to 

 assimilate nitrogen, so that from a prac- 

 tical point of view a waste takes place of 

 this important and comparatively ex- 

 pensive item of plant food. Prom the 

 point of view of economy the matter is 

 affected in another way. Next to nitro- 

 gen, potash is the most costly element 

 that has to be supplied to plants ; thus 

 its supply in excess leads to waste oa this 



