370 



THE AGRICULTURAL NEWS. 



November 26, 1910. 



nnheated soil, was also kept, undLT exactly simi- 

 lar conditions. The temperature at which the soil 

 Avas maintained, during keeping, was about 15°C., in 

 both cases. It was found, in saturating the soils with 

 water, that those which had been heated required less 

 for the purpose than those to which this treatment had 

 not been given. In order to gain an idea of the extent 

 of possible accidental variations, complete duplicatf 

 experiments were devised: theie showed that such varia- 

 tions were very small. The results obtained indicated 

 that very definite and complex changes occurred during 

 the time that the soils were being kept. In the case 

 of the unheated soils, or those which had not been heat- 

 ed to any large extent, the st>luble matter increased 

 during the time of heating while, with the more highly 

 heated ones, it diminished; these changes affected both 

 the organic and the inorganic matter in the soils. There 

 was an intermediate condition, ranging between temper- 

 atures of heating of -50 to 10.5C., in which there was 

 little or no change in composition. Such were the 

 results obtained iu the soils kept in the open pans. 



As regards the soils that were kept in sealed Masks, 

 those which were less heated suffered, as before, an in- 

 crease in the soluble matter; but the diminution in this, 

 that was obtained with the highly iieated soils in the 

 open pans was not experienced. In the second instance 

 as a matter of fact, the |iro]iortion of organic matter 

 remained almost constant, or even increased slightly: 

 this was also the case with the organic matter. It is thus 

 indicated strongh^ that the lessening of soluble matter 

 in heated s)il exposed to the air is due to oxidation, 

 while the presence or absence of air has nothing to dn 

 with the increase in the solu'cle matter that takes place 

 on keeping the less heated soil. Examination of the 

 results obtained throughout the course of the experi- 

 ments shows that, even with the le.ss heated soil, there 

 is a decrease in tlie aimiunt of soluble matter during 

 the first ten days. That this decrease continues longer 

 in the case of the more highly heated soils is due to tlie 

 fact that these contain a larger proportion of oxidizible 

 matter. 



In the investigations, attention was given to the 

 extent to which the reduction of the amount of soluble 

 matter in a heated soil is effected by the action of bacte- 

 ria, in addition to atmospheric oxidation. It was 

 shown that this reduction takes place largely in the 

 absence of bacteria, even when the soil is not periodic- 

 ally moistened. A matter of mterest and importance 

 to the soil investigator is the demonstration that air- 

 dried samples of soil change in composition during the 

 time that they are being stored, previous to analysis. 



The last portion of the work was concerned more 

 directly with the comparison of the results of the examin- 

 ation of the .soils, in the way described, with the effects 

 on the germination of seeds. It was found that, in the 

 case of the heated soil kept in pans, the decrease in 

 soluble matter was accompanied by a lessening of the 

 retardation of the germination of seeds. A further 

 fact shown was that, though the soluble matter formed 

 in the highly heated soil prevented germination to 

 some extent, the soluble matter that is formed gradu- 

 ally in the less heated soils has no such action. In any 

 case, as regards the first soils, the effect had entirely 

 disappeared by the 10()th day, even though the ulti- 

 mate extent of the decrease in soluble matter had nob 

 been reached. Thus it is shown that not all the soluble 

 substance formed in the more highly heated soils is of 

 a toxic nature: but that even after it has disappeared, 

 much of the soluble matter produced by this heatinc is 

 left. Former e.'cperimenls had indicated that the 

 amount of retardation of germination was proiiorti'jual 

 to the increisc in the quantity of insoluble organic mat- 

 ter; the subseqiu^nt experiments, however, d-monstra'e 

 that this is not always the case. 



Additional ol)Sei-\ations were made f r the purpose 

 of ascertaining if any periodical variation takes place, 

 in regard to the soluble matter in the soil, tmder ordin- 

 ary conditions. These showed that the amount of 

 organic and inorganic matter decreased throughout the 

 earlier part of the year, but increased siibsecpiently. 

 It is suggasted that this may be ilue, under the con- 

 ditions of the tri^l, simply to the effect of rainfall acting 

 through the exposed soil surrounding that which was 

 purposely j)roiected for the experiment. 



To summarize the more imjiortant results of the 

 w'ork, it is shown that the retarding influence on the 

 germination of seeds, evidencetl by heated soils, is gradu- 

 ally reduced when these are exposed, moist, to the air, 

 even when bacterial action is not possible: but that this 

 is not the ca.se when they are kept moist in the absence 

 of air. This would indicate that the destruction of the 

 poisonous substance is due to oxidation. Secondly, 

 that toxic matter of the kind found in quantity ia heated 

 soil appears to be present in all soils, but that its 

 amount in those whirh ha\e not been heated is so small 

 that it is soon oxidized. Lastly, air-dried soils, whether 

 they have been heated or not, suffer a reduction in solu- 

 ble constitiu'nts, and in toxic substances where these 

 were originally present, after being kept for some 

 moiiths — a reduction closely similar to that shown by 

 moist soils kept in air for about ten days. 



