Vol. VII. No. 164. 



THK AGRICULTURAL NEWS. 



251 



SCIENCE NOTES. 



Effect of Carbon Bisulphide on Soil Fertility. 



The researches of the p;wt few \'ears in soil 

 bacteriology have piodaced information of fhc greatest 

 interest to agriculturists. Ever3'one has oonie to 

 recognize the rAle that i.s accorded to niicro-organif; life 

 ill the soil ill the luitiition of higher plant.s, but it has 

 yet to be deiimn.-tiatrd what are the relative impor- 

 tance of the jihysical, chemical, and bacteriological 

 factors in sdII Kilility. Enough has been accomplished, 

 ho\v,ever. In indicate liiat the biol'igical processes are 

 •of equ.d iiii|i'jitiiK;e with clienncal, and physical 

 processes in liie suil, and theri'fiie de.serve equal con- 

 sidenui'iu in studies of soil fertility. Our kinnvledge 

 of soil-b.ic".erlological processes h;is gained much fiDin 

 the investigalidiis nf the effect nf c.irb'in bisulphide on 

 soil fertility, and, tlieref ire. the fiiluwing abstract from 

 Bulletin No. 1!)4< 'd' the (Iffice of Experiment Stations, 

 United States Depirtmeiit of Agriculture, will be of 

 interest : — 



In 1894- it wa.s observed that the application ot carljon 

 bisulphide increased the crop-producing power of the soil, 

 and it w-as shown that grape-sick soils in Oennany could 

 frequently hi rejuvenated by the use of thi-< substance. The 

 e.\act manner of its acti' 111 was imperfectly inidersto<id until 

 it was demonstrated that it exerted icertain influenci/s upon 

 the bacteria in the soil. It had been found that under normal 

 conditions there is a certain equilibrium lietween the vaiimis 

 groups of soil bacteria,, and later it was shovvii that when 

 carlion bi~ul|iliide was applierl to the soil, its bacteri.d inlialii- 

 tants were iiijuied, 'J'lic amount of injury varies with cluuig- 

 ing conditions of temperature, moisture, and amount of 

 ■carbon bisnljilude ajujlied, iis well as the cliu'ation of 

 its action. 'J'he ditt'ercnt bacterial species are ilepressud 

 in their development in varying degrees, but this 

 depression iHsappears after a certain interval, and is 

 followed liy a very rapid development. The yencial cquili 

 brinm amongst tlie ditterent soil bacteria is thus destroyeil, 

 and the new development may follow along certain cliannels, 

 resulting not only in an increase in number of soil l)acLeria, 

 but also an abnormal predominance of certain species. 

 The new conditions thus establi-shed for a time favfuir 

 .a more ready utilization of the stores of soil nitrogen, 

 and also the lixation of atmospheric nitrogen by certain 

 bacterial sjjecies. It is for this reason that the aiiplication 

 of carbon bisulphide is followed after a time by a very 

 •decided increase in crop yields as compared with the corres- 

 ponding yields for soils not treated. It has further been 

 demonscrated that soils treated with carbon bisulphide 

 showed not only an increase in their total nitrogen content, 

 but also that this increase was the result of the more vigorous 

 growth fif the iiitrogen-fixing Aiouhncter siiecies. 



This action of cirboii bisul[)lii(le iriay jiossibly 

 assist lis, partially ;it least, to understand the peculiar 

 •effects that have been noticerl when green manuring 

 has been practised with miistaid, rye, and other non- 

 leguminous crops. It has been noted frequently that 

 ■crops of several iion-leguniinous plants when ploughed- 

 in in the green state, have been followed, on nitrogen- 

 poor soils, by gieatlj' increased crops. Particular 

 interest amongst scientific agriculturists has been 

 awakened in England in certain experiments wdth 



mustard as green dressings, and the results obtained 

 are being closely followed. 



Drs. Voorhees and Lijiman in their Bidktin, 

 allude to experiments with this plant as follows : — 



.So striking were the benefits in some instances from 

 green manuring with mnstard that it was proposed in some 

 (juarters to include inn.stard among the 'nitrogen gatheiers' 

 rather than among the 'nitrogen c-onsumers.' The first 

 communication of Hellriegel and Wilfarth on the nitrogen- 

 fixation liy legumes, made twenty years ago, and the 

 stimulated research in this field that followed their work, soon 

 furnished conclusive jiroof that mustard is incapable of 

 utilizing atmospheric nitrogen for its growth. But, as 

 Heinze pjiiits out, there may have been more or less just! tica- 

 tion for this belief, .so far as the indirect influence of mustard 

 is concerned. It would seem that at times the action of 

 mustard is not unlike that of carbon bisulphide in affecting 

 the bacterial flora of the soil, and it really appears from facts 

 already known that tlic green mu.stard substance in the .soil 

 retards llir (le\elopnienl of the acid-forming species of 

 bacteiia and encourages the growth of the nitrogen-fixing 

 A'.rtfi)ii'irli;r .species. 



Other plants, such as buckwheat, rye, etc., have 

 given similar results as mustard, and it is possible that 

 similar effects may be produced on the bacterial fioraof 

 the soil. The question of the use of non-leguminous 

 plants for green dressings has frequently lieen brought 

 feiruard m several West Indian Islands, n,nd it is hoped 

 tliat experimental evidence as to their value may soon 

 be forth'-oming, whilt^thc question of a possibihty of 

 a ■ b iclerial weeding,' by which harmful bacteria may 

 be reduced in niimberSj^and beneficial ones stimulated, 

 is worthy of consideration. The effect that the toxic 

 substance excreted from the roots of plants (see Aijri,- 

 cultaral A^fws, Vol. VII, p. 238) may have upon the 

 bacteria in the soil, or how far green dressings m.ay 

 neutralize its action, has yet to be investigated. 



CACAO FROM BRITISH HONDURAS. 



The following note on a sample of cacao received 

 from British Honduras appears in the Bulletin uf the 

 Iiiipi'vial Ivi^tituti', Vol. YI, No. 1 : — 



The sample of cacao from British Honduras was received 

 at the lm|)erial Institute from the Colonial Office in 1907. 



The sanqile weigheil 30 lb., and consisted of fairly large, 

 plump, well fermented beans, which posse.s.sed a good ' break ' 

 and were free from mcjuldiness. Its taste was mild and not 

 excessively bitter. 



The i)uality was similar to that of the best grades of 

 Trinidad cacao which reach the English market, and a firm of 

 brokers to whom it was submitted stated that it would meet 

 with a ready sale in this country. It was valued in London 

 at from 110.<. to lll.<. jier cwt., in bag.s, .subject to the usual 

 conditions, at a time when the finer grades of Trinidad cacao 

 were (pKited at llO.v. to llL'.<. per cwt. 



The enormous value of the sisal hemp industry to 

 'Yucatan planters is well known. During the year 1907, the 

 hemp exported reached 100,773,946 kilograms, valued at 

 •$24,874,318. The quantity shipped is somewhat greater 

 than the exports of tiie previous year, but owing to a fall in 

 price, the return obtained was considerably less than that of 

 1906. (British Comular Re^iort.) 



