Vol. XIII. No. 313. 



THE AGRICULTURAL NEWS. 



133 



CHEMICAL NOTES. 



REPORT ON AGRICULTURAL CHEMISTRY 



FOR 1913. 



The annual review of the progre.ss made in agricultural 

 chemistry and vegetable physiology during 1913, is contained 

 in Volume X of the reports issued by the Chemical Society 

 of London. 



Whilst nothing of very exceptional importance has to 

 be recorded for the year, activity in research has been well 

 maintained and much useful work has been accomplished, 

 especially in connexion with soil chemistry and bacteriology. 



In connexion with the atmosphere, the amount of 

 combined nitrogen present has received attention, and it has 

 been shown that in regard to this source of supply for the 

 plant the rain is of no great importance Various interest- 

 ing analyses of rain-water for other substances has been 

 made. 



Chemical work on the soil has, as already stated, been 

 very considerable. Reference may be made to the rainera- 

 logical vork of the United States Bureau of Soils, and to 

 the study of the plasticity of clay and elfects of frost on 

 soil colloids. Considerable further progress has been made 

 in isolating the organic constituents of the soil, a subject 

 which has been referred to from time to time in this journal. 

 The question of the existence of humic acids has been 

 investigated and seems now to be definitely settled in favour 

 of the old idea. 



A typical line of research during 1913 has been the 

 effects of partial sterilization of soil both by heat and by 

 antiseptics. This subject has also been dealt with in the 

 AgricultHral News. In connexion with the partial sterili- 

 zation of soils, some interesting re.sults have been obtained 

 which throw light on the action of lime on soil organisms. 

 It has been shown that lime has an antiseptic action 

 intermediate between the effects produced by heating soil 

 and by volatile antiseptics, respectively. Lastly, work has 

 been done on heating soils to high temperatures and in 

 connexion with losses of ammonia from soils. 



Ammonification, nitrification and denitrification have 

 received attention. A new denitrifying organism has been 

 obtained from the soil. An interesting series of experiments 

 has been described on the ammonification of dried blood in 

 soils, as affected by antagonism between anions. The results 

 are of considerable interest and suggest possibilities in 

 reclaiming the large areas of alkaline soils. In the course of 

 investigation on the production of nitrates in soils, an 

 interesting result has been that the rotation of crops increases 

 the number of bacteria as compared with continuous 

 cropping. Work has been conducted on the production of 

 ammonia from amino acids in the soils. Fixation of 

 elementary nitrogen by Azolohacler n-oot'occum was found to 

 be increased when air was actuated by pitch blende, some- 

 what better results being obtained with weak than with 

 stronger radioactive intensity. 



In regard to investigation work on plant nutrition, the 

 Rothamsted experiments during the year have appeared to 

 negative the soil toxin theory which received considerable 

 support in America. In general, results on plant nutrition 

 have tended to show clearly that the composition of soil 

 solution is by no means constant but varies according to the 

 manures applied. The growth of crops depends not merely 

 on the amount of plant food but within wide limits on the 



concentration of the solution. The continuous growth of the 

 same crop for sixty or seventy years does not leave behind 

 a specific toxin having an injurious effect on the same or 

 other crops. 



Whilst the question of the direct assimilation of 

 ammonium salts by plants may be considered to have been 

 decided during the year under review beyond doubt, a good 

 deal remains to be done in connexion with the behaviour of 

 different plants towards ammonium salts and the effect of 

 the compounds as compared with nitrates. An important 

 point in this problem is the question of preference for 

 nitrate or ammonium during different stages of growth, and 

 also the question as to whether the ammonium salts are 

 assimilated as a whole. An interesting line uf work has 

 been that conducted on the assimilation of nitrites. 



The report under review concludes with a summary of 

 the work done with plant stimulants and manures. The 

 prevailing idea now is that most poisonous substances will 

 act as stimulants to plant growth in certain states of dilution. 

 Reference is made to the pot experiments conducted with 

 rice and vines, also to the experiments in England which 

 consisted in the application of lithium during germination, 

 the effect of zinc salts on wheat, ammonium sulphate on 

 barley, etc. Experimental work has been done on the effect 

 of ammonium sulphite as a manure, together with the 

 manurial value of cyanamide and molasses. 



Effect of Carbon Bisulphide and Toluene 



on Nitrification. — It is stated in the Journal of the 

 Chemical Societi/ (February 1914) that nitrification in the 

 soil is not affected by O^lcc. of toluene in 100 grammes of 

 soil. A large amount of toluene generally has an inhibitory 

 effect for a short time. Carbon bisulphide at the rate of less 

 than about Ic.c. to 108 grammes of soil has no appreciable 

 effect; more than Ic.c. generally retards nitrification for 

 a time; even with as much as .5c.c, the retarding effect is 

 soon overcome. The conclusion is drawn that toluene or 

 carbon bisulphide applied to fields will not materially affect 

 nitrification if applied at the rate of O'lc.c. per 100 grammes 

 of soil. 



Effect of Arsenic on Soil Processes.— The 

 arsenic of 'insoluble' insecticides is not completely insoluble 

 according to the publication mentioned in the previous note — 

 the greatest amount is soluble when Paris green has been 

 used and the least with lead arsenate. The trisulphide seems 

 to become more soluble after remaining in soils. Ammonifi- 

 cation and nitrification are not decreased by the pre.sence of 

 100 per million of sodium arsenate in soils rich in calcium 

 and iron; smaller amounts may have a considerable stimulat- 

 ing action. Zinc arsenite, lead arsenate and arsenate 

 trisulphide stimulate ammonification and are only toxic when 

 comparatively large amounts are present. All the arsenic 

 compounds stimulate nitrification which, however, is checked 

 by large amounts of Paris green and arsenic trisulphide. The 

 only substance which is likely to be injurious to soil bacteria 

 in practice is Paris green, and the quantity added will have 

 to be large. The beneficial action of arsenic on ammonifica- 

 tion and specially nitrification, is attributed partly to 

 stimulation and partly to its influence on injurious species 

 of bacteria. 



