16 SOIL FERTILITY. 



" The humus content of all soils, principally from con- 

 siderations of a physical character, might be appreciably 

 increased with advantage. There is reason to think, as 

 will be shown later on when dealing with the mechanical 

 characteristics of the soils under discussion, that the 

 mechanical Avorking and the water holding capacity of 

 certain of the lands of the north would be improved by an 

 increase in the organic supplies of these soils. In the 

 Mallee, where, owing to a limited rainfall, especial benefits 

 from the increased moisture point of view might be expected, 

 the humus content, it will be noted, reaches its lowest figure." 



In the foregoing pages particular attention has been 

 devoted to lime and organic matter on account of their 

 many functions in connection with soil fertility. 



It is of course known that the total amount of 

 phosphoric acid and potash in the soil is not increased by 

 liming and green manuring, but that these operations 

 increase the availability of the phosphoric acid and potash 

 of the soil — deficiency of phosphoric acid or potash can 

 only be rectified by application of fertilisers containing 

 these substances. 



Liming or marling was a practice of the ancients, as was 

 also the ploughing in of legumes and farm yard manure, 

 and from then up to the present time these operations have 

 been conducted by agricultural communities to maintain 

 and increase soi' fertility. Therefore it is not claimed 

 that anj^thing new has been stated in connection with the 

 subject, but it is thought that reiteration of the value and 

 importance of the methods taken to assure soil fertility 

 is still very necessary. 



In modern times artificial fertilisers have been used, 

 a,nd their value when correctly applied has received Avide 

 recognition . 



Soils in many parts of the world have been for various 

 reasons abandoned, one reason being that of soil exhaus- 

 tion, but now in many cases these soils, their fertility restored 

 by correct treatment, are again being cultivated. Thus 

 it may be stated that though there are many soil problems 



