254 THE MONTHLY BULLETIN. 



This pronouncement of the chemists as to the fertility of land, though 

 all chemists now hold a greatly modified view of the relations of the 

 chemicals in a soil to the fertility of the soil, was first vigorously com- 

 bated by a theory of soil-fertility advanced by soil-physicists. The 

 physicists hold that the quantity of mineral foods in a soil is of far 

 less importance than the quantity of water, and that the cultivator 

 should largely devote his energies to controlling the moisture in the 

 land so that the mineral salts may be readily dissolved and be made 

 available as a plant food. They insist upon the very great importance 

 in soil-fertility of such other physical factors as temperature, aeration 

 and the texture of the soil. The most radical advocates of the physical 

 theory declare that chemical fertilizers are of little or no value for 

 the food they add to the soil. 



It seems to an onlooker that the chemists have not sufficiently recog- 

 nized the importance of the physical condition of the soil in their 

 teaching. At any rate it is now certain that in practice in every field 

 of agriculture, following instructions from chemistry, far too much 

 importance is attached to putting chemicals into the soil and far too 

 little to the physical means of making available for food the unavailable 

 material now there. While many of the differences between chemists 

 and physicists are more suited to controversy than to real practice 

 in soil-fertility, yet much good is bound to come from the discussions 

 now going on between the sciences they represent. 



It is not quite a quarter of a century since the writer received instruc- 

 tion in what was called agricultural chemistry. The teacher, a pioneer 

 chemist, gave, or supposed he gave, instruction regarding the fertility 

 of soils. He had received his light from the flood of light which began 

 with Liebig. .The instruction ran, in brief, that chemistry could provide 

 for practically all the needs of soil-fertility. To the teacher and student 

 of that day the now important fields of soil physics and bacteriology 

 were wholly arid and unproductive. The centuries old riddle of how 

 leguminous crops fertilize land had then just been solved by the dis- 

 covery that bacteria, the underworld of life, take nitrogen from the 

 air and store it in the roots of clover, peas, beans and their like. This 

 revelation, one of the most important in all time for agriculture, has 

 been followed in quick succession by one astonishing discovery after 

 another by the bacteriologist. Now it is proved that the earth is 

 literally alive with bacteria — a living earth, not a dead, inert one — an 

 earth teeming with good, bad and indifferent organisms. 



Now we are told that not only do bacteria store nitrogen in the roots 

 of legumes but other bacteria change the ammonia formed by the decay 

 of plant and animal matter into nitrates in the soil, thus saving and 

 putting into better form nitrogen which otherwise would have escaped 

 into the air. Still other of the soil bacteria decompose nitrates, setting 

 free nitrogen, which unless combined with the salt of some mineral 

 escapes and is lost. We are taught that the farmer can control the 

 rate of nitrification and denitrification in the soil by drainage, aeration, 

 cultivation, and by regulating the temperature of the soil. Thus, 

 literally, bacteria can be domesticated and set to work at making 

 nitrogen for the farm. As, often, fertility of the soil is determined 

 by the rate at which nitrates are formed, the regulation of the bacteria 

 of nitrification is an important factor in keeping up the fertility of 



