8 March, 1907.] The Outlook for Agricitltiire. I3r 



element to the soil in the form of .artificial fertilizers. On the wheat 

 lands the addition of nitrogen actually diminishes the yield. Where the 

 rainfall is above 25 inches the addition of nitrogen increases the yield 

 of grain and also the total weight of the crop, but the former effect is 

 not so marked as the latter. For the most part the soil appears to be 

 abundantly furnished with nitrifying bacteria ; all leguminous crops flourish 

 luxuriantly, and so far as our experiments have gone, the addition of 

 nitrogen-fixing bacteria to the seed has had no apparent effect in assisting 

 the crop. Considering that all animal excreta and farm-yard manure 

 are proportionate! v very rich in nitrogen, it appears practicable, by good 

 farm methods, not onl\ to keep up, but also to rapidly increase the 

 amount that exists on \irgin land. The nitrogen problem is important, 

 but bv scientific methods it may easily be solved, and at present I think 

 there is no indication that it will become as important as it is in Europe 

 and America. While we are not yet able to explain all the phenomena, 

 it appears certain that in this respect we are favoured either by the soil 

 or the climate ; nitrates seem to accumulate rapidlv. For market garden 

 crops and potatoes, esneciallv on the lighter sandv soils, it is found that 

 a light dressing of nitrogen, in readily available form, insures a profitable 

 crop ; but for cereals, and for ordinarv fodder crops, the cost of supplying 

 the necessarv amount of nitrogen is not a serious problem to the farmer, 

 and it appears to me that with improved farm practice, it will become 

 even less formidable as general farming takes the place of cereals alone. 

 The presence of lime in suitable amount facilitates the process of 

 rendering the nitrogen a\ai]aljle, as will be noticed later on. 



The Problem of Phosphoric Acid. 



Turning next to phosphoric acid, we may look upon this constituent as 

 being, in a special sense, the controlling factor in the development of 

 plant 'life. It is remarkable that the world supply of nitrogen, phosphoric 

 acid, and lime at present available for the use of existing plants and 

 animals has all been combined and rendered available by past generations 

 of living things. Originally all the phosphoric acid of the soil formed 

 part of the most ancient rocks in the form chiefly of apatite. It has 

 graduallv become concentrated on the surface of ihe soil li\ the inter- 

 vention of plants and animals. Comparatively little is lenehed out of 

 the soil by the rain, onlv the barest trace being present in sea water. In 

 the case of rock phosphate, the seaweed growing in shallow depths has 

 collected this trace of phosphoric acid from the sea water, just as the 

 coral and other organisms have collected the lime. From the sea-weed 

 the conversion into rock phosphate is accomplished through the medium 

 of the fish and birds. We are at the present time drawing on the 

 accumulations that have been made in past geological ages. In the case 

 of the phosphoric acid of the soil this has been gradually accumulatmg in 

 the surface lavers through the medium of the plant, but its concentration 

 is brought about through the intervention of the animal. The neadv 

 insoluble phosphate of lime of the bones of vertebrates cfrers striking 

 analogies to the similarl\- insoluble carbonate of lime of the shells of 

 invertebrates. 



It is often asked if there is not a certaintv in the e:nl\ luture that 

 such soils will l)ecome exhausted of their supi)lv of jjlant AkjiI. .and liecorae 

 unprofitable. So long as live stock are kept in considerable numlx'rs. this 

 is not likelv to happen. I take it that Australian soils owe their small 



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