14 SOIL FERTILITY. 



has been made, the variation in the amounts of plant food 

 material (with the exception of lime) as shown by the 

 analyses of the soils that have been considered has very 

 similar extremes. And with favourable physical and 

 biological conditions, crops, suitable to ' the particular 

 climate in which their cultivation is undertaken, under 

 correct soil management should give yields comparable with 

 those obtained in other countries. 



That the obtaining and maintaining of correct soil 

 moisture content in our soils is the factor that must claim 

 first attention, is recognised. The utilisation of the rain- 

 fall to the greatest extent is therefore necessary, and it is 

 desired to mention here that humus and tilth of soil have a 

 very great influence upon soil moisture. Humus, by 

 improving the tilth increases the water absorptive power 

 of the soil by permitting of easier penetration of rain, and 

 the presence of this material in the soil increases the re- 

 tention of water absorbed. 



The improvement of tilth by the application of lime has 

 already been mentioned. 



It has been shown that twenty-seven per cent of the 

 Queensland soils now being considered, have been found 

 to have a low humus content, and considering the value 

 humus has in connection with soil moisture, it is apparent 

 that the increase and maintenance of the organic matter 

 in these soils is of the very greatest importance. And 

 acknowledgment of the importance of this subject is 

 evidenced by the fact that green manuring forms part of 

 some cultural systems adopted in this country. 



That this matter receives consideration in countries 

 where it has been shown the soils contain somewhat similar 

 amounts of organic matter, is illustrated by the following 

 statements. 



Thus HiJgard* writes in connection with the humus 

 of the soils of California : — 



" That excessive aeration results in serious loss of 

 humus, as well as nitrogen, is very obvious in the arid 



*0p. cit. 



