SOIL AND SUBSOIL. 



I2 3 



waters containing lime salts, the ulmic substances are neutral- 

 ized and precipitated. Such neutralization, preferably by 

 means of lime, is the first step towards the reclamation of lands 

 bearing " sour " vegetation. The acid reaction characterizing 

 the ulmic substances is also characteristic of many woodlands, 

 notably in the United States of the soils of the " Long-leaf- 

 pine " region of the Cotton States, both upland and lowland, 

 as well as of many deciduous forests in northern climates. 

 Hence liming, whether artificial or natural, effects a most not- 

 able improvement, together with a marked change of vegeta- 

 tion, in these lands. 



It has been long known that after long-continued cultivation, soils 

 originally of neutral or slightly basic reaction become acid : and the 

 liming of such lands is an ancient practice in Europe. The matter, 

 however, received but scant attention until Wheeler and Hartwell, of 

 the Rhode Island Experiment Station, demonstrated the almost univer- 

 sal acid condition of the older lands of that State, and the excellent 

 effects produced by neutralization with lime, or even with the alkali 

 carbonates. 1 The current neutralization of the humus-acids is unques- 

 tionably one of the cardinal advantages of calcareous lands ; for such as 

 contain only small amounts of lime carbonate will of course become acid 

 more quickly under cultivation. 



Humin Substances. In the presence of only a moderate 

 amount of moisture, therefore under the influence of a more or 

 less rapid circulation of air, and in the presence of earthy 

 carbonates (especially that of lime) to prevent the formation 

 of acids, or to neutralize them as formed, the normal process 

 of humification occurs; mainly under the influence of fungous 

 instead of bacterial growths. The various molds take a 

 prominent part in the conversion of the vegetable substance 

 into black, neutral, insoluble humus compounds. Such fungous 

 vegetation is always accompanied by the evolution of carbonic 

 gas, and the resulting fungous tissues are markedly richer in 

 nitrogen and carbon than the substance of the higher plants 

 from which they were derived (see chapt. 9). Com- 

 parative analyses show that in the normal process of humifica- 

 tion of vegetable substances, oxygen and hydrogen are elimi- 



1 Reports of the Rhode Island Exp't Station, 1895. an( ^ ff 



