946 MANURES AND MANURING 



In the colorimetric method, the Hquid was first centrifuged, and after 

 the indicator sohition had been added, the coknir produced was measured 

 by comparison with that of a sohition of known hydrogen-ion concentra- 

 tion. The indicators used were methyl red, the sodium salt of phenolsulph- 

 one-phthalein, phenolphthalein, the recently prepared tetrabromophenol- 

 sulphone-phthalein, diprop}^ red, and brcmothymol sulphone-phthalein. 

 Each soil sample was tested with two of these indicators. The results were 

 in close agreement with one another, and with the elect rometric determina- 

 tion. The hydrogen-ion concentration expressed as the hydrogen-ion 

 exponent of Sorensen, v?ried from 4.4 to 8.6, the exponent 7 indicating 

 neutrality. The application of the colorimetric method to soils under 

 field conditions is now being investigated. 



M.^NTjREs 734 - Relation of Green Manures to the Failure of Certain Seedlings.— frede. b. 



."iND (Agricultural Bacteriologist, Agricultural Experiment Station of the University of 



MAXTJRiis'G Wisconsin), in Journal of Agricultural Science, Vol. V, No. 25, pp. 1161-1176, 2 plates. 



Washington, D. C, March 20, 191 6. 



In a previous report it had been shown that if green manures are turn- 

 ed under and cotton planted immediately^ a decrease in germination may 

 result, while if the operation is repeated three weeks later germination 

 is perfectly normal. 



With a view to studying this phenomenon, fresh experiments in jars 

 and in the field were made with green manures of crimson clover, in the pro- 

 portion of about I per cent, of the soil, and with different kinds of seeds. 

 The effect of some products of decomposition, heat, bacteria and fungi was 

 also studied. 



The investigations as a whole confirmed the injurious action of green 

 manure on seed germination. It appears to be due to some parasitic fun- 

 gus {Rhizoctonia sp.). During the first period of decomposition of the green 

 manure, many fungi develop, some of them having a destructive action on 

 germs. Oil seeds in particular are very liable to be injured. Starchy seeds 

 on the contrary are highly resistant. Cotton and so^-a seeds are extremely 

 sensitive to green manure. The germination of flax, pea-nuts, hemp, 

 mustard and clover is likewise reduced, though to a less extent, by the 

 presence of decomposing vegetable tissue. The germination of buckwheat, 

 corn, oats and wheat is not affected by green manure. 



The injurious action of green manure on oil seeds is confined mostly 

 to the first stages of decomposition. The experiments undertaken appeared 

 to show that two weeks after the green manure has been turned in, it no 

 longer has any serious harmful effect on the germination of oil seed. The 

 addition of small quantities of lime appears to increase the injury to germi- 

 nation, the greater or less rapidity of the latter to some extent influencing 

 the amount of such injury. Thus slow germination is marked by a high 

 percentage of diseased seedlings. 



Appended is a bibliography of 21 works relating to the question. 



