PRESIDENT S ADDRESS. 7 



Silica and iron are also essential, but these are universally present. 



Now, having told the farmer what chemicals are necessary for 

 him to have in his soil if he wants his crops to flourish and his 

 stock to thrive, I can easily imagine his saying : " How am I to 

 find out whether these chemicals are there and whether in a suitable 

 form ? " My answer to him is that he can only do so accurately 

 by having his soil analysed : yet he can also make a very shrewd 

 guess that if he or others have year after year been cultivating 

 the ground without ever having put anything back into it he has 

 been lessening the quantity of chemicals nature at first provided, 

 and therefore he would be justified in assuming that the soil was 

 short of most of these necessary ingredients, and he would be 

 doing well were he to attempt to artificially restore what had 

 been in the past removed. 



It may interest some sceptical farmers to know the result of 

 certain experiments carried out in the Transvaal regarding the 

 accuracy of the contention that the chemicals I have mentioned 

 are necessary for plants to live upon. The result of these experi- 

 ments was published in the Agricultural Department Journal of 

 October last. Grains of barley were grown in glass vessels con- 

 taining water, and to this water were added small, carefully- 

 weighed quantities of those chemicals I have mentioned as being 

 necessary for plant life. In some cases the whole of the chemicals 

 were added whilst in separate other cases one or other of these 

 chemicals was left out. During the growth of the plants the glass 

 vessels in which the barley was growing were kept in the dark, 

 and only the leaves and stems were exposed to the light, in imitation 

 of nature's plan. The barley in the pots where all the chemicals 

 had been added, grew, reached maturity, and produced grains. 

 In those where the nitrogen was withheld the barley grew vigorously 

 at first, but when the nitrogen contained in the seed itself was 

 exhausted the plant died of nitrogen starvation. Where no 

 phosphoric acid was added there was practically no root develop- 

 ment at all and the plant soon died off. From this experiment it 

 would appear that to get a good lot of roots there must be an 

 ample supply of phosphoric acid. Where no potash was added 

 the barley grew for a considerable time but never made any appear- 

 ance of producing grain. Where no lime was supplied the barley 

 grew at first very well, but gradually got weaker and died of lime 

 starvation. 



The question now to be considered is how deficiences in plant 

 food are to be supplied to the soil. In good soils these chemicals 

 actually exist but not in the required form for absorption by plants. 

 The best system is to have good cultivation and have the soil 

 moved about and kept open. This allows oxygen to get at the 

 roots of the plants, and it facilitates the work of the beneficial 

 bacteria which have the task of converting mineral nitrogen into 

 nitrates to be consumed by plants. Where the soil is poor either 

 in consequence of its original poverty or its having become so, 

 through bad cultivation, plant foods can only be replaced by a 

 manure. To ascertain accurately the form of manure which is 

 necessary, an exact analysis of the soil must be made to find out 



