930 EXPERIMENT STATION RECORD. 



However, if it is limited to two, or even one sample, let the total depth be that to 

 which the intended crop is known to feed." The author suggests that in the study 

 of soils by chemical methods it be assumed "that the availaljie plant food rarelj'- 

 extends to a depth of more than 12 in., and that plants penetrating below that depth 

 do so for the purpose of obtaining moisture." Such an assumjition would simplify 

 and increase the accuracy of sampling. 



Development and distribution of nitrates in cultivated field soils, F. H. 

 King and A. R. WiiiTSox [Wisconxiu Sta. Rpt. 1901, pp. 210—2Sl,fig><. 5). — Tn con- 

 tinuation of previous inve.stigations (E. S. R., 13, pp. 24, 229) determinations of 

 nitrates were made twice each month in the uppei 4 ft. of the plats used in former 

 experiments, "the objei-t being to learn what diffei'ences may result with differences 

 of season and with change of croi>. 



"The work with the total soluble salts as indicated by Whitney's electrical method 

 has been discontinued because it was learned that while his method gave results 

 which agreed fairly well with the gravimetric method for the surface foot of <jur 

 soils, there was a wide disagreement when the second, third, and fourth feet wei'e 

 compared, the gravimetric method giving more soluble salts with the sands and less 

 with the clays than the electrical method did, while there was an approximate 

 agreement with the loams which are intermediate in texture." 



It is shown that as an average for plats which were cropped last year there w as 

 131.4 lbs. per acre more of nitrates in the surface 4 ft. in the spring of 1901 than in 

 1900, and 291.93 lbs. more at the beginning of Septenil)er. 



The nitrates in the plant (leaves and stems) grown mu the various jilats wei'e 

 determined at different stages by the following method: 



"A sample of plants from the field was first chopped tine ami mixed. From this 

 mixture 20 gm. were weighed out, placed in a wedgwood mortar, thoroughly 

 crushed, and finally worked up with 250 cc. of distilled water placed in the mortar; 

 20 cc. of this solution was drawn off into an evaporating dish and heated over a 

 water bath for a few minutes, to partly coagulate the organic matter. It was then 

 allowed to cool, after which 6 to 8 drops of subacetate of lead (U. S. P.) are added, 

 with stirring to precipitate albuminoids. Then about 1 gm. of powdered animal 

 charcoal, previously digested in sulphuric aci<l and very thoroughly washed, is added, 

 allowed to stand for an hour with occasional stirring, and then filtered and waslied 

 with distilled water, making it finally up to 100 cc. 



"The method of jsrocuring a clear solution is that of A. Pagnoul (E. 8. R., 8, j). 

 386), sliglitly modified. An aliquot of this solution is then evaporated and treated 

 as described in [a previous bulletin] (E. S. R., 13, p. 230). . . . 



"To determine the moisture content of the sample, for computation usually 100 gm. 

 of the cut material was dried." 



The results, together with those of determinations of nitrates in the surface foot of 

 soil, made as a I'ule the preceding day, are reported in detail. They show "that in 

 the case of the corn the nitrates, whether expressed in terms of the plant moisture 

 or of the dry matter in the plant, have, in general, decreased with the degree of 

 maturity in the crop; but with the potatoes or clover this relation is not so marked. 



"Where the determinations have been made in the leaves and stems separately 

 the results show a greater concentration of nitrates in the stems, as would be 

 expected if the nitrates are broken down in the leaves or converted into organic 

 nitrogen compounds. 



" Everywhere the degree of concentration of nitrates in the sajj of the plant stems 

 is much higher than it is in the soil moisture. This appears very strange from the 

 physical point of view and much more in harmony with the views formerly lield by 

 Berthelot and Andre, that nitrate of potash is continually formed in the stems of 

 plants, Init not accepted as correct by most authorities at present." 



