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THE AGRICULTURAL NEWS. 



October 23, 1915. 



plays the leading part in the formation of the oxygen 

 required b) the roots of the rice. Certain cultural 



i! s after harvest also help to conserve a store 



ofoxygenin the bo the arrival of the 



rains. 



1 1 i- evidenl I herefore, that the preseni f oxygen 



in essentia] factor in soil fertility as regards the 

 ivth of crops. It is equally necessary in relation to 

 the developmenl of bacteria. This latter aspect of the 

 subject is sufficiently interesting and important to 

 warrant special consideration. In the first place it 

 maybe pointed out thai an adequate supply of air is 

 especially import ant for leguminous plants. As is well 

 known, the roots of these plants are provided with 

 special factories (nodules) in which, by means of 

 bacteria, atmospheric nitrogen is worked up into com- 

 plex nitrogenous substances which the plants can use as 

 ■ I. Both oxygen and nitrogen, the chief constituents 

 of the air, are essential raw materials for these factories 

 and must therefore be provided if these plants are to 

 thrive. This can only be done by efficient soil 

 ventilation, and by the provision of ample means of 

 gaseous interchange between the soil and the air. 

 In connexion with this, Howard goes so tar as to 

 -;i\ ilei-e can lie noipiestioii that the future of Java 

 indigo (a leguminous plant ) in Bihar depends on soil 

 ventilation. . . the preseni chances of the industry 

 are most hopeful if only the planters are willing to 

 place the cultivation oi the crop on a proper basis and 

 give up their present methods. 



( In another page m this issue tin: conclusions 

 arrived at by J. H. Walton 4 - 1! A., B.Sc, concerning the 

 fixation of nitrogen by the free-living organism 

 Azotobacter in Indian soils are given, from our 

 present point of view his most interesting conclusion is 

 the beneficial influence of good cultivation ofthe soil 

 (i.e., aeration ) upon the organism's act i\ ities. In one 

 experiment two plots were taken, and in the case ofthe 

 first, the soil was left untouched while in the second 



plol the --oi] was cultivated \\eekl\ to a depth of li 



inches. At the beginning of tic « cperiment, Plot 1 

 contained 65*2, and 1'lot 2, 63'8 milligrammes of 

 nitrogen per 100 gms. of soil respectively. Alter the 



elapse of tell Weeks, the soils Were |, I 1 1 , 1 1 \ - . < I . alld 



Plot I was found to contain <>T4 and Plot 2, 66'5 

 milligrammes of nitrogen per 100 grms. oi soil. In 

 Plot I. therefore, there was ■> loss of 0*8 milligrammes, 



while in Plot -. which was cultivated, there was 



a gain of -7 milligrammes. The importance, indeed 



• if, .... f ni of An, ■■;. ulturt in I 



Bacteriological Series, Vol. I, No. I. 



the necessity ofagood supply of oxygen for azotobacter 



has been noted by all previous investigators. S. K. 

 Ashby, B.Sc, formerly of Rothamsted and now 

 Microbiologist to tic Jamaica Department of Agri- 

 culture, stronglj emphasizes this in his paper on the 

 assimilation of atmospheric nitrogen,} and although 

 he has isolated the organism from cultivated soils in 

 Jamaicaf it had not at the time of writing thi paper 

 referred to below been found in old pasture ami old 

 meadow land. Its absence was no doubt due to acidity 

 and anaerobic conditions induced by the permanent 

 cultivation. 



The reference which has just, been made to 

 permanent crops may arouse a desire in the reader's 

 mind to enquire how the roots of grass fare as regards 

 aeration. Probably the roots of grass secure their air 

 supply through being so near to the surface of the soil. 

 Further, an important agent of aeration is the common 

 earthworm and possibly ants and termites. It will lie 

 remembered as well that of all cultivations pastures 

 require drainage most. This secures not only the 

 removal of superfluous water bul also means thesuction 

 of air through the soil. Gaseous interchange is also 

 brought about bj the law of diffusion of gases and by 

 variation in atmospheric pressure and temperature. 

 These explanations would appear sufficient to meet, 

 what might first be regarded as an anomaly. 



In connexion with grass, an interesting comment, 

 on the work at Woburn on the effects of grass on the 

 roots of trees, is made by Howard in the paper referred 

 to at the beginning of this article. The Duke of 



Bedford and S. U. Bickering at the above-menti d 



place, consider that grass roots give off a toxin 

 which poisons the tree roots. This toxin however, 

 has not yel been isolated, bul its presence is inferred 

 from the results of numerous experiments. These 

 authors have now studied the influence of grass on 

 other crops like tobacco, and have come to the conclu- 

 sion that 'every growing crop results in the formation 

 of a substance which is toxic to the growth of other 



plants and still more so to itself. Howard states thai 

 the results obtained in the ease of tobacco are exceed- 

 ingly like those observed at 1'usa when tobacco is 



water-logged or grown on heavy lands which have 

 been green-manured. It is well known that the roots 

 of the tobacco crop require a gri al deal of air. and it is 

 also known that green manuring results m the pro- 

 duction of much carl lioxide in the soil, it s,-,.ms 



probable that the Woburn results, in which the wash- 

 es* lr ' in Bulletin, S ol. \ 111. p. 96. 

 tji Igricultural Scicnc; Vol. II, p. 35-51, 



