RELATION OF FERTILISERS TO SOIL FERTILITY. 5 



We know further that certain fertilisers benefit certain crops. We know, 

 for example, that the application of superphosphate will probably increase 

 the yield of wheat and other cereals ; but this knowledge is not derived from 

 information supplied by the composition either of the soil or the wheat 

 plant. 



The wheat crop, grain and straw, contains only half the quantity of 

 phosphoric acid that it does of nitrogen, and much less than it does of 

 potash, and yet we know that neither nitrogenous nor potash manures are 

 anything like as effective as soluble phosphates in increasing the yield. Nor 

 does soil-analysis help us to any extent. The soil may be comparatively rich 

 In phosphates and poor in nitrogen and potash, and still phosphatic 

 manuring is the more effective. Our wheat soils in the semi-dry country are 

 indeed lacking for the most part in humus and nitrogen, and yet it is by the 

 -application of superphosphates and not of nitrogenous manures that crops 

 are successfully grown. 



The case of leguminous plants is of a similar nature ; crops like peas and 

 beans and clover contain more nitrogen than other fertilising ingredients, 

 and yet manuring with nitrogen is resultless, and the ingredients which are 

 -most beneficial are potash and phosphates. Here again, it is immaterial 

 whether the soil is rich or poor in nitrogen or rich in potash. The com- 

 position of fruit-trees doers not explain why potash manuring should be of 

 such special benefit, nor is there any satisfactory explanation why the 

 mangel crop which contains nearly four times as much potash as ihe potato 

 <jrop should not benefit by the application of this ingredient, whereas it is 

 an essential, a " dominant " ingredient for manures applied to potatoes. 



I do not wish to press this point further, but simply to accentuate my 

 statement that the composition either of the crop or of the soil is not an 

 infallible guide to the nature of the manuring required. In fact, we have 

 not advanced much on the principles enunciated by Ville. We still manure 

 with a complete manure, paying special attention to the ingredient which, is 

 *' dominant " for the particular crop. 



Explanations of these peculiarities will no doubt be forthcoming. In the 

 case of leguminous crops, we are acquainted with the process by which they 

 obtain the required nitrogen from the air and are independent of soil 

 nitrates or nitrogenous manuring. 



In the case of wheat, I have suggested an explanation, which I venture to 

 think is the correct one, of the rather extraordinary phenomenon that the 

 application of nitrate or other nitrogenous manure which is essential to 

 the production of wheat in Europe and America is without effect on crops 

 grown locally, its place being taken by superphosphate.* 



Shortly stated, this explanation lies in the different conditions as to nitri- 

 fication prevailing here and in Europe and America during the growth of the 

 crop. In the latter countries the wheat commences to grow in soil from which 

 the nitrates have been washed out, and in which nitrification does not take 



* Agricultural Gazette, New South Wales, vol. xvii., p. 29. 



