1912] on Recent Advances in Agricultural Science. r)21 



There are two possible recuperative actions to make up for the crops 

 removed —the Azotobacter working upon the carbonaceous matter 

 returned in the turnip crop, and the growth of the clover, for that 

 crop as we know gathers nitrogen from the atmosphere by means of 

 the organisms living in the nodules upon its roots. AVhen neither 

 clover IS grown nor are the roots put back the soil is slowly losing 

 nitrogen ; when either occurs singly a fair production is maintained 

 without loss of soil nitrogen ; when both take place during the rotation 

 the average removals from the soil become as high as thirty-iive 

 bushels per acre of wheat, thirty-four of barley, and more than two 

 tons of clover hay, yet the soil is if anything gaining rather than losing 

 in fertility, though no extraneous nitrogen is being introduced. 



Thus we see that we can maintain indefinitely a production of over 

 four quarters per acre of wheat, and their equivalent in other crops, by 

 natural agencies alone without recourse to external supplies of nitro- 

 gen, provided we repair the small annual losses of phosphoric acid 

 and potash, which of course cannot be regenerated from the atmo- 

 sphere. But such a level of production, though equal to the average 

 of the British Isles, is below that which a modern intensive farmer 

 must attain, and the lesson that we have to bear in mind is that at a 

 higher level, say that of five quarters of wheat, the wasteful actions 

 of which we have spoken are increased out of all proportion. Hence 

 we have to add as manurial nitrogen not merely the difference between 

 that contained in the extra quarter of wheat, but four to five times 

 that amount to repair the waste, and so on to an even greater extent 

 if we still further raise the fertiUty and the production. 



The essential wastefulness of highly intensive agriculture such as 

 must be forced upon the race as the new countries fill up is a serious 

 question, but the prospect of reducing the waste is not entirely hope- 

 less. The losses, as we have seen, are due to bacteria, which attack the 

 nitrogen compounds with liberation of nitrogen gas, the particular 

 bacteria doing this being most active in soils rich in organic matter, 

 until at Rothamsted we only recover in the wheat crop about one 

 quarter of the nitrogen applied in the heavy dressing of farmyard 

 manure. The problem before us is to bring the soil bacteria under 

 control, and we already begin to see in various ways that such control 

 is not impossible. For example, the researches of Drs. Russell and 

 Hutchinson at Rothamsted have already proved that in one simple 

 way we can so rearrange the micro-fauna and flora of the soil as to 

 obtain a much higher duty from the reserves of nitrogen therein 

 contained. 



It is too long a story to enter upon now. I can only briefly say 

 that by putting the soil through various processes of partial steriliza- 

 tion, such as heating or treatment with antiseptics, like chloroform or 

 toluene, we can eliminate certain organisms which keep in check the 

 useful bacteria in the soil — i.e. the bacteria which break down the 

 nitrogen compounds lo the state of ammonia, a form assimilable by 



