320 Agricultural Gazette of N.S.W. [May 3, 1920^ 



Nothing will exhaust the soil more quickly than lime if used alone. Bear 

 and Salter* found that the use of quicklime in excess of the needs of the soil 

 caused a loss of nitrogen, phosphorus and organic matter from the surface 

 soil considerably larger than the increased yields produced would justify. 

 When the organic matter is maintained and the supply of plant food material 

 is kept up, the application of lime may be profitable. In America the cost of 

 ground limestone (which is most largely used) is only about 5s. or 6s. per ton, 

 while here this substance is quoted at about 30s. per ton, with agricultural 

 (or air-slaked) lime at nearly double this price. This precludes the application 

 of lime on a large scale in this State; but experiments are in progress to 

 determine the value of lime on maize soils in those districts where the rainfall 

 is high and where much loss of this substance from the soil may be 

 expected on account of leaching. 



Do Commercial Fertilisers Impoverish the Soil? 



In many districts the cry is heard from farmers that commercial fertilisers^ 

 impoverish the soil. Such farmers argue that it has been their experience- 

 that once they start to use commercial fertilisers (especially superphosphate) 

 they are compelled to continue the practice, for if they leave off, they find 

 the yields poorer than on land to which no fertiliser had been applied. This 

 is undoubtedly in many cases the truth, but its full significance has not been 

 realised — it certainly does not constitute an argument in favour of no- 

 fertiliser ; the fact that increased and profitable yields have been realised 

 seems to have been lost sight of. As has been shown, fertilisers add to the 

 soil only a portion of the plant food removed by the crops, with the inevitable 

 result that the total plant food in the soil gradually decreases and the land 

 itself is steadily impoverished under continuous culture or one-crop farming. 

 But fertilisers supply this plant food in an easily available form, whereas 

 there is a limit to the use which can be made of the plant food in the soil 

 because of the large amount of it which is highly insoluble. This is mainly 

 the reason why fertilisers give increased yields, and explains to some extent 

 why fertilisers must be continued. The increased crops obtained from the 

 use of fertilisers take more plant food from the soil than poorer crops grown 

 without fertiliser ; and it is the first business of every farmer (and an 

 economically sound practice) to rob the soil of its fertility by making the land 

 produce its utmost in crops. The farmer should recognise, however, that he 

 cannot have his cake and eat it too. If he does not wish his land to become 

 poorer, he should be content with poor crops. 



Successive good crops of maize or other crops in continuous culture without 

 rotation (whether due to good seasons, good cultivation or fertilisers) must 

 make the soil poorer in available plant food, and this is what makes fertilisers 

 necessary (especially phosphatic fertilisers, like superphosphate, bonedust, 

 &c., l>ecause there is no other means of supplying the element phosphorus) 

 and all the more necessary on soil to which fertilisers have been previously 

 added. There can be no room for complaint so long as fertilisers give a 



* Wtist Virginia Agr. Expt. S-d,. i.iiil. IGO (1916). 



