Scientific Agriculture. 



518 



[December, 1910, 



in which form the element is available 

 for the nourishment of growing plants. 

 This process is called nitrification, and 

 the transformation of organic nitrogen 

 into nitrates undoubtedly results, we 

 are told, from the action of more than 

 one species of bacteria, and takes place 

 in three or more different steps. They 

 ai'e chilled and cease work in cold 

 weather, and cannot live without a 

 supply of oxygen. Stirring the soil 

 admits air into it and this accelerates 

 nitrification. Nor can they live in a 

 sour soil, hence the benefit of lime to 

 infertile areas. In dense unstirred sour 

 soil varieties of bacteria are found which 

 denitrify it : that is, set free the nitro- 

 gen so that it returns to the air. The 

 operations and action of nitrifying 

 bacteria have been closely studied in 

 connection with the growth of legu- 

 minous plants. It has been found that 

 they are most susceptible to the value of 

 nitrogen. Where it exists in the soil 

 they pay little attention to it, but where 

 it is lacking: they accumulate it in 

 nodules on the roots p*nd produce stores 

 of the element. In practicable hus- 

 bandry this has been generally recog- 

 nised, and the introduction of legumin- 

 ous crops into systems of rotation is 

 testimony to the value of the work of 

 the unseen agriculturists. 



At the meeting of the British Associ- 

 ation for the Advancement of Science 

 held in England a few weeks ago great 

 interest was aroused among agricultural 

 experts by the announcement that a 

 micro-organism had been discovered 

 which was destroying these beneficent 

 bacteria. Eminent agricultural scien- 

 tists regarded the discovery as the most 

 noteworthy since the discovery of the 

 fixation of nitrogen by bacteria. It has 

 been clearly established that where the 

 nitrifying bacteria were present in the 

 soil the fertility of plants was manifest ; 

 it has even been asserted that it was in 

 proportion to the bacteria in the soil, 

 Occasions have arisen where it was diffi- 

 cult to discover the cause of the disap- 

 pearance of bacteria from areas of land 

 and its consequent infertility. The 

 statement uoav made is that a definite 

 micro-organism has been isolated which 

 lives upon the bacteria of the soil. 

 Nitrogenous soil was found to contain 

 six million bacteria per gramme, btit 

 after treatment which killed the deadly 

 micro-organisms the number was in- 

 creased to sixty million. Means of des- 

 troying the micro-organism is by the 

 use of bisulphide of carbon, toluene, and 

 boiling water. From what we have said 

 regarding the vitality of the spores of 

 bacteria it can be understood how earth 



which had been boiled or heated to 212 

 deg. recovered its nitrogenous character 

 when cooled and moistened. The spores 

 survived, and as soon as the conditions 

 became favourable began to multiply at 

 the rate ot seventeen million in twenty - 

 four hours. It has recently been dis- 

 covered that soil which has been ster- 

 ilised and restored to its ordinary condi- 

 tion is most fertile and useful for start- 

 ing the growth of plants from seeds. It 

 is now considered that the increase of 

 nitrifying bacteria — the unseen agricul- 

 turists — has been prevented by the 

 presence of the micro-organism. It is 

 larger than the bacteria and preys upon 

 them freely. Now that it has been iso- 

 lated and its characteristics determined 

 hopes are entertained that easy means 

 of dealing with it may be discovered. 

 In the meantime our agriculturists must 

 be on the alert to discover whether it is 

 as destructive in our soils as in that of 

 Rothamsted, England. 



THE MAINTENANCE OP SOIL 

 PRODUCTIVITY. 



(Prom the Agricultural Nexus, Vol. IX., 

 No. 219, September, 1910.) 

 In most parts of the world agricul- 

 tural practice has reached the stage of 

 full recognition, in individual cases, of 

 the necessity of keeping up the fertility 

 of the soil by approved methods. An 

 understanding of the needs of the soil 

 has been gained, so that there is a 

 decreasing tendency to take whatever 

 this may yield without treating it in 

 ways which will prevent its exhaustion. 

 This phase of the methods of agricul- 

 tural production is naturally of the 

 greatest importance, especially as it 

 enables the area concerned in that pro- 

 duction to be conserved effectively. 



The principles of the maintenance of 

 soil productivity are, however, usu- 

 ally employed in a narrow way only. 

 They are considered to relate to matters 

 on a particular estate, or group of 

 estates, or to the production of one 

 given crop. This is insufficient where 

 the agricultural welfare of a whole 

 district, or colony, is concerned. Such 

 welfare depends mainly on the level of 

 the agricultural efficiency of the in- 

 habitants, and therefore on the extent 

 to which agricultural methods suited to 

 the particular conditions are in vogue. 

 Individual effort may be of use in limited 

 areas, but in countries where the means 

 of production are generally inferior, 

 those areas, alone, will profit by it, and 



