D PRESIDEXT S ADDRESS. 



is poor in vegetable or organic matter can be greatly nnprovea 

 in quality. It can be easily understood that leguminous crops 

 do not need artificial fertilisers which contain nitrogen. By 

 manuring the soil with farmyard refuse a large number of special 

 bacteria, whose speciality it is to convert nitrogen into ammonia, 

 are replaced in the soil, and the greatest benefit is thereby derived. 

 Phosphoric acid is of the very greatest importance to all kinds of 

 crops. Unfortunately in this country it is very often in such 

 small quantities that it is too little for what is required. The 

 European standard is .01 per cent, of phosphoric acid or one in 

 one hundred, but in this country it is in many cases only one-fifth 

 of that amount — in fact, not nearly enough for good farming. 

 Phosphoric acid is, as I have already said, usually present in the 

 soil in the form of a phosphate, i.e., in combination with lime 

 or some other like substance, but to be absorbed by plant life 

 it has to be set free from this combination. This, it is generally 

 understood, is accomplished by means of the acidity of the soil. 

 This acidity acting upon the mineral phosphates liberates the 

 phosphoric acid and enables it to be consumed. I have here 

 referred to acidity of the soil. This acidity, I should explain, 

 arises from the decomposition of vegetable matter where there 

 is too small an amount of lime and magnesium present to neutralise 

 it. This acidity, if too great, injuriously affects plant life, but the 

 exact manner of its doing so is not quite understood. It will 

 be observed that the presence of lime is necessary in the soil to 

 counteract the acidity and, in combination with phosphoric acid, 

 to form phosphates, yet if there is too much lime in the soil it 

 will check the solution of the mineral pho?iphates and thereby 

 prevent the release of the phosphoric acid in the manner required 

 by the plants. It can be understood, therefore, how necessary 

 it is in the growing of crops to ascertain whether you have too 

 much acidity in the soil or not. If you have too much acidity 

 it can be corrected by the judicious addition of lime, care being 

 taken, of course, that you do not add too much. If there is too 

 little acidity in the soil, it can be increased by the judicious use 

 of farmyard or green manures which will by their decompositioji 

 add to the acidity and thus bring about the liberation of the 

 phosphoric acid. It has even been proposed to spray alkaline 

 soils with very dilute nitric acid. 



Potash is another very important element for plant life. It 

 prolongs the growing period of a plant and its production of 

 starchy and sugary products. Fortunately it is generally present 

 in sufficient quantities in our soils, except perhaps in those of an 

 exceedingly light, sandy nature. Potash should be present in the 

 soil in the ratio of about one in one thousand, and the vast majority 

 of our soils have this amount. 



Calcium or lime is most necessary in the soil, not only on account 

 of the part which it plays in combination with nitrogen and phos- 

 phoric acid, as already described, but also because it is itself a 

 plant food. 



Magnesium forms part of the food of plants and, though present 

 in'small amounts, there is generally sufficient for any ordinary crop. 



